# Patent

## Title
Piezoelectric ceramic, method for manufacturing piezoelectric ceramic,  piezoelectric element, and electronic device

## Abstract

A piezoelectric ceramic contains a main component, Mn as a first auxiliary component, and a second auxiliary component containing at least one element selected from the group consisting of Cu, B, and Si. The main component contains a perovskite metal oxide having the following general formula (1):

(Ba1-xCax)a(Ti1-yZry)O3(0.100≦x≦0.145,0.010≦y≦0.039)  (1)

The amount b (mol) of Mn per mole of the metal oxide is in the range of 0.0048≦b≦0.0400, the second auxiliary component content on a metal basis is 0.001 parts by weight or more and 4.000 parts by weight or less per 100 parts by weight of the metal oxide, and the value a of the general formula (1) is in the range of 0.9925+b≦a≦1.0025+b.

## Background
TECHNICAL FIELD
The present invention relates to a piezoelectric ceramic and more particularly to a lead-free piezoelectric ceramic and a method for manufacturing the lead-free piezoelectric ceramic. The present invention also relates to a piezoelectric element, a multilayered piezoelectric element, a method for manufacturing a multilayered piezoelectric element, a liquid discharge head, a liquid discharge apparatus, an ultrasonic motor, an optical apparatus, a vibratory apparatus, a dust removing device, an image pickup apparatus, and an electronic device, each including the piezoelectric ceramic.
BACKGROUND ART
In general, piezoelectric ceramics are ABO3 perovskite metal oxides, such as lead zirconate titanate (hereinafter referred to as “PZT”). However, PZT contains lead as an A site element, and its effect on the environment is regarded as a problem. Thus, there is a demand for piezoelectric ceramics of lead-free perovskite metal oxides.
One known piezoelectric ceramic of a lead-free perovskite metal oxide is barium titanate. In order to improve the characteristics of barium titanate, materials based on barium titanate are being developed. PTL 1 and NPL 1 disclose materials having an improved piezoelectric property in which the A site of barium titanate is partly substituted by Ca and the B site is partly substituted by Zr. However, these materials disadvantageously have a Curie temperature as low as 80° C. or less and therefore cause depolarization and deterioration in piezoelectric property under a high-temperature environment, such as in a car in summer. Furthermore, these materials disadvantageously have a low mechanical quality factor and therefore tend to generate heat and, upon the application of an alternating voltage, cause depolarization.
PTL 2 and NPL 2 disclose materials in which the A site of barium titanate is partly substituted by Ca and to which Mn, Fe, or Cu is added. These materials have a higher mechanical quality factor than barium titanate but disadvantageously have a poor piezoelectric property.
CITATION LIST
Patent Literature


    PTL 1 Japanese Patent Laid-Open No. 2009-215111
    PTL 2 Japanese Patent Laid-Open No. 2010-120835


Non Patent Literature


    NPL 1 “Journal of Applied Physics”, 2011, Vol. 109, 054110-1 to 054110-6
    NPL 2 “Japanese Journal of Applied Physics”, 2010, Vol. 49, 09MD03-1 to 09MD03-4


SUMMARY OF INVENTION
Technical Problem
The present invention addresses these problems and provides a lead-free piezoelectric ceramic having a high and stable piezoelectric constant and a high and stable mechanical quality factor in a wide operating temperature range and a method for manufacturing the lead-free piezoelectric ceramic.
The present invention also provides a piezoelectric element, a multilayered piezoelectric element, a method for manufacturing a multilayered piezoelectric element, a liquid discharge head, a liquid discharge apparatus, an ultrasonic motor, an optical apparatus, a dust removing device, an image pickup apparatus, and an electronic device, each including the piezoelectric ceramic.
Solution to Problem
In order to solve the problems described above, the present invention provides a piezoelectric ceramic, which contains a main component, Mn as a first auxiliary component, and a second auxiliary component containing at least one element selected from the group consisting of Cu, B, and Si. The main component contains a perovskite metal oxide having the following general formula (1):

(Ba1-xCax)a(Ti1-yZry)O3(0.100≦x≦0.145,0.010≦y≦0.039)  (1)

wherein the amount b (mol) of Mn per mole of the metal oxide is in the range of 0.0048≦b≦0.0400, the second auxiliary component content on a metal basis is 0.001 parts by weight or more and 4.000 parts by weight or less per 100 parts by weight of the metal oxide, and the value a of the general formula (1) is in the range of 0.9925+b≦a≦1.0025+b.
Advantageous Effects of Invention
The present invention can provide a lead-free piezoelectric ceramic having a high and stable piezoelectric constant and a high and stable mechanical quality factor in a wide operating temperature range.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic view of a piezoelectric element according to an embodiment of the present invention.
FIG. 2A is a schematic cross-sectional view of a multilayered piezoelectric element according to an embodiment of the present invention.
FIG. 2B is a schematic cross-sectional view of a multilayered piezoelectric element according to another embodiment of the present invention.
FIG. 3A is a schematic cross-sectional view of a liquid discharge head according to an embodiment of the present invention.
FIG. 3B is a schematic perspective view of the liquid discharge head illustrated in FIG. 3A.
FIG. 4 is a schematic view of a liquid discharge apparatus according to an embodiment of the present invention.
FIG. 5 is a schematic view of a liquid discharge apparatus according to an embodiment of the present invention.
FIG. 6A is a schematic view of an ultrasonic motor according to an embodiment of the present invention.
FIG. 6B is a schematic view of an ultrasonic motor according to another embodiment of the present invention.
FIGS. 7A and 7B are schematic views of an optical apparatus according to an embodiment of the present invention.
FIG. 8 is a schematic view of an optical apparatus according to an embodiment of the present invention.
FIGS. 9A and 9B are schematic views of a dust removing device including a vibratory apparatus according to an embodiment of the present invention.
FIG. 10A is a schematic perspective view of a piezoelectric element of a dust removing device according to an embodiment of the present invention.
FIG. 10B is a side view of the piezoelectric element illustrated in FIG. 10A.
FIG. 10C is a schematic perspective view of the piezoelectric element illustrated in FIG. 10A.
FIGS. 11A and 11B are schematic views illustrating the vibration principle of a dust removing device according to an embodiment of the present invention.
FIG. 12 is a schematic view of an image pickup apparatus according to an embodiment of the present invention.
FIG. 13 is a schematic view of an image pickup apparatus according to an embodiment of the present invention.
FIG. 14 is a schematic view of an electronic device according to an embodiment of the present invention.
FIG. 15 is a phase diagram illustrating the relationship between the x-values and the y-values of piezoelectric ceramics according to Examples 1 to 38 and Comparative Examples 1 to 12 of the present invention. The x-values and the y-values surrounded by the dotted line are within the scope of claim 1.



DESCRIPTION OF EMBODIMENTS
Embodiments of the present invention will be described below.
A piezoelectric ceramic according to an embodiment of the present invention contains a main component, Mn as a first auxiliary component, and a second auxiliary component containing at least one element selected from the group consisting of Cu, B, and Si. The main component contains a perovskite metal oxide having the following general formula (1):

(Ba1-xCax)a(Ti1-yZry)O3(0.100≦x≦0.145,0.010≦y≦0.039)  (1)

The amount b (mol) of Mn per mole of the metal oxide is in the range of 0.0048≦b≦0.0400, the second auxiliary component content on a metal basis is 0.001 parts by weight or more and 4.000 parts by weight or less per 100 parts by weight of the metal oxide, and the value a of the general formula (1) is in the range of 0.9925+b≦a≦1.0025+b.
The term “main component” means that a principal component for exhibiting the piezoelectric property is the perovskite metal oxide having the general formula (1). Thus, the piezoelectric ceramic may contain a minute amount of inevitable impurities resulting from its manufacture.
Regarding Perovskite Metal Oxide
The term “perovskite metal oxide”, as used herein, refers to a metal oxide having a perovskite structure, which is ideally a cubic structure, as described in Iwanami Rikagaku Jiten, 5th edition (Iwanami Shoten, published on Feb. 20, 1998). A metal oxide having a perovskite structure is generally represented by a chemical formula of ABO3. In a perovskite metal oxide, elements A and B in the form of ions occupy particular positions of a unit cell referred to as the A site and the B site, respectively. For a cubic unit cell, the element A occupies the vertexes of the cube, and the element B occupies the body-centered position of the cube. The element O as an oxygen anion occupies the face-centered positions of the cube.
In the metal oxide having the general formula (1), the metallic elements at the A site are Ba and Ca, and the metallic elements at the B site are Ti and Zr. Part of Ba and Ca may occupy the B site. Likewise, part of Ti and Zr may occupy the A site.
In the general formula (1), although the molar ratio of the B site element to the element O is 1:3, small variations in the molar ratio (for example, 1.00:2.94 to 1.00:3.06) are within the scope of the present invention, provided that the metal oxide has the perovskite structure as the primary phase.
The term “primary phase” means that a peak having the highest diffraction intensity in the X-ray powder diffraction of a piezoelectric material belongs to the perovskite structure. The metal oxide may be of a “single phase” almost entirely occupied by crystals having the perovskite structure.
The perovskite structure of the metal oxide can be determined by structural analysis using X-ray diffraction or electron diffraction.
The term “ceramic”, as used herein, refers to an aggregate of crystal grains (also referred to as a bulk), that is, a polycrystalline, containing a metal oxide as the base component and sintered by heat treatment. The term “ceramic” also includes a ceramic processed after sintering.
The value a of the general formula (1), which represents the ratio A/B of the number of moles of Ba and Ca at the A site to the number of moles of Ti and Zr at the B site, is in the range of 0.9925+b≦a≦1.0025+b. The value b denotes the amount (mol) of first auxiliary component Mn per mole of the metal oxide. When the value a representing the ratio A/B is smaller than 0.9925+b, this tends to result in abnormal grain growth and a decrease in the mechanical strength of the metal oxide. When the value a representing the ratio A/B is larger than 1.0025+b, this results in an excessively high grain growth temperature, making sintering of the metal oxide impossible. The phrase “making sintering of the metal oxide impossible” means that the piezoelectric ceramic has a low density or contains many pores and defects. Most of the first auxiliary component Mn occupies the B site. An increase in the value b representing the amount of Mn results in an increase in the number of B sites, which requires a corresponding increase in the value a.
The value x of the general formula (1), which represents the molar ratio of Ca at the A site, is in the range of 0.100≦x≦0.145. A value x of less than 0.100 results in structural phase transition in the operating temperature range (for example, −20° C. to 100° C.), thereby adversely affecting the durability of the piezoelectric ceramic. A value x of more than 0.145 results in a deterioration in piezoelectric property. The value x is preferably in the range of 0.100≦x≦0.140, more preferably 0.105≦x≦0.130.
The value y of the general formula (1), which represents the molar ratio of Zr at the B site, is in the range of 0.010≦y≦0.039. A value y of less than 0.010 results in a deterioration in piezoelectric property. A value y of more than 0.039 results in structural phase transition in the operating temperature range (for example, −20° C. to 100° C.) and low temperature stability of the piezoelectric ceramic. The value y is preferably in the range of 0.010≦y≦0.035, more preferably 0.015≦y≦0.030.
Composition Analysis Method and Composition of Piezoelectric Ceramic
The composition of a piezoelectric ceramic according to an embodiment of the present invention may be determined by any method. The method may be X-ray fluorescence analysis, ICP spectroscopy, or atomic absorption spectrometry. The weight ratio and the molar ratio of the elements of the piezoelectric ceramic can be determined by using any of these methods.
The first auxiliary component is Mn. The amount b (mol) of Mn per mole of the metal oxide having the general formula (1) is in the range of 0.0048≦b≦0.0400. A piezoelectric ceramic according to an embodiment of the present invention containing the amount of Mn in this range has an improved mechanical quality factor without reduction of piezoelectric constant. The term “mechanical quality factor” refers to a coefficient that represents elastic loss resulting from vibration in the evaluation of a piezoelectric ceramic as an oscillator. The mechanical quality factor is observed as the sharpness of a resonance curve in impedance measurement. Thus, the mechanical quality factor is a coefficient that represents the sharpness of resonance of an oscillator. An increase in mechanical quality factor results in a decrease in energy loss due to vibration.
An improvement in insulation property or mechanical quality factor ensures long-term reliability of the piezoelectric ceramic when the piezoelectric ceramic is driven as a piezoelectric element by the application of a voltage.
A value b of less than 0.0048 results in a low mechanical quality factor of less than 400. A low mechanical quality factor disadvantageously results in an increase in the power consumption of a resonance device that includes a piezoelectric element composed of the piezoelectric ceramic and a pair of electrodes. The mechanical quality factor is preferably 400 or more, more preferably 600 or more. In this range, no excessive increase in power consumption occurs in practical operation. A value b of more than 0.0400 unfavorably results in a deterioration in piezoelectric property or the occurrence of hexagonal crystals, which do not contribute to the piezoelectric property.
Mn can occupy the B site. Mn can have a valence of 4+. In general, Mn can have a valence of 4+, 2+, or 3+. In the presence of conduction electrons in crystals (for example, in the presence of oxygen vacancies in crystals or in the presence of donor elements occupying the A site), Mn having a valence of 4+ can trap the conduction electrons and improve insulation resistance by reducing its valence to 3+ or 2+. In terms of the ionic radius, Mn having a valence of 4+ can easily substitute for the main component Ti of the B site. Mn having a valence of less than 4+, such as 2+, acts as an acceptor. The presence of Mn as an acceptor in perovskite crystals results in the formation of holes or oxygen vacancies in the crystals.
In the presence of a large amount of Mn having a valence of 2+ or 3+, holes cannot be compensated for with oxygen vacancies alone, and the insulation resistance decreases. Thus, Mn can mostly have a valence of 4+. A minor proportion of Mn may have a valence of less than 4+ and occupy the B site of the perovskite structure as an acceptor or form oxygen vacancies. Mn having a valence of 2+ or 3+ and oxygen vacancies can form defect dipoles and thereby improve the mechanical quality factor of a piezoelectric material.
The second auxiliary component content of a piezoelectric ceramic according to an embodiment of the present invention on a metal basis is 0.001 parts by weight or more and 4.000 parts by weight or less, preferably 0.003 parts by weight or more and 2 parts by weight or less, per 100 parts by weight of the metal oxide.
The second auxiliary component content is a weight ratio of the second auxiliary component to 100 parts by weight of the constituent elements of the metal oxide having the general formula (1) on an oxide basis, which is calculated from the amounts of Ba, Ca, Ti, Zr, Mn, and metals of the second auxiliary component of the piezoelectric ceramic measured, for example, by X-ray fluorescence analysis (XRF), ICP spectroscopy, or atomic absorption spectrometry.
The second auxiliary component is at least one of Cu, boron (B), and Si. B and Si can segregate at interfaces between crystal grains of the piezoelectric ceramic. This reduces a leakage current flowing through the interfaces between crystal grains and increases insulation resistance. Cu can dissolve in crystal grains and increase insulation resistance. At least 0.001 parts by weight of the second auxiliary component in the piezoelectric ceramic can increase insulation resistance. Less than 0.001 parts by weight of the second auxiliary component undesirably results in reduced insulation resistance. More than 4.000 parts by weight of the second auxiliary component in the piezoelectric ceramic undesirably results in a reduced dielectric constant and a deterioration in piezoelectric property. The weight ratio G1/G2 of the weight G1 of Si to the weight G2 of boron (B) may be in the range of 2.0≦G1/G2≦3.8. This range results in particularly suitable insulation resistance. The Si content may be 0.003 parts by weight or more and 1.000 parts by weight or less. The Cu content may be 0.100 parts by weight or more and 2.000 parts by weight or less. The boron (B) content may be 0.001 parts by weight or more and 1.000 part by weight or less.
A multilayered piezoelectric element has a thin piezoelectric ceramic layer between electrodes and therefore requires durability in a high electric field. Because of its particularly high insulation resistance, a piezoelectric ceramic according to an embodiment of the present invention is suitable for a multilayered piezoelectric element.
A piezoelectric ceramic according to an embodiment of the present invention may contain the metal oxide having the general formula (1) and a third auxiliary component other than the first auxiliary component and the second auxiliary component, provided that the third auxiliary component does not adversely affect the characteristics of the piezoelectric ceramic. The amount of the third auxiliary component may be 1.2 parts by weight or less per 100 parts by weight of the metal oxide having the general formula (1). More than 1.2 parts by weight of the third auxiliary component may result in a deterioration in the piezoelectric property or the insulation property of the piezoelectric ceramic. The metallic element content of the third auxiliary component except Ba, Ca, Ti, Zr, Mn, Cu, B, and Si may be 1.0 part by weight or less on an oxide basis or 0.9 parts by weight or less on a metal basis per 100 parts by weight of the piezoelectric ceramic. The term “metallic element”, as used herein, includes metalloid elements such as Ge and Sb. When the metallic element content of the third auxiliary component except Ba, Ca, Ti, Zr, Mn, Cu, B, and Si is more than 1.0 part by weight on an oxide basis or more than 0.9 parts by weight on a metal basis per 100 parts by weight of the piezoelectric ceramic, this may result in a marked deterioration in the piezoelectric property or the insulation property of the piezoelectric ceramic. The total amount of Li, Na, Al, Zn, Sr, and K of the third auxiliary component may be 0.5 parts by weight or less on a metal basis per 100 parts by weight of the piezoelectric ceramic. When the total amount of Li, Na, Al, Zn, Sr, and K of the third auxiliary component is more than 0.5 parts by weight on a metal basis per 100 parts by weight of the piezoelectric ceramic, this may result in insufficient sintering. The total amount of Y and V of the third auxiliary component may be 0.2 parts by weight or less on a metal basis per 100 parts by weight of the piezoelectric ceramic. When the total amount of Y and V of the third auxiliary component is more than 0.2 parts by weight on a metal basis per 100 parts by weight of the piezoelectric ceramic, this may make polarization treatment difficult.
A piezoelectric ceramic according to an embodiment of the present invention may contain Nb inevitably contained in a commercially available raw material for Ti and Hf inevitably contained in a commercially available raw material for Zr.
The main component having the general formula (1), the first auxiliary component, and the second auxiliary component can constitute 98.5% by mole or more of a piezoelectric ceramic according to an embodiment of the present invention. The perovskite metal oxide having the general formula (1) preferably constitutes 90% by mole or more, more preferably 95% by mole or more, of the piezoelectric ceramic. The parts by weight of the first auxiliary component, the second auxiliary component, and the third auxiliary component may be measured by any method, including X-ray fluorescence analysis, ICP spectroscopy, and atomic absorption spectrometry.
Structural Phase Transition Point
A piezoelectric ceramic according to an embodiment of the present invention may have no structural phase transition point (hereinafter also referred to as a phase transition point) at a temperature in the range of −20° C. to 100° C.
Generally known barium titanate has an orthorhombic-to-tetragonal transition temperature (hereinafter referred to as To→t) of approximately 17° C. and a tetragonal-to-orthorhombic transition temperature (Tt→o) of approximately 5° C. While repeatedly passing through these structural phase transition points, the piezoelectric ceramic may gradually be depolarized because of variations in unit cell volume and polarization axial direction, resulting in a deterioration in piezoelectric property. Thus, barium titanate is difficult to use in a wide temperature range. A piezoelectric ceramic according to an embodiment of the present invention has To→t of less than −20° C. and is unlikely to cause the problem of barium titanate. A piezoelectric ceramic according to an embodiment of the present invention has a Curie temperature of 100° C. or more and can maintain its piezoelectricity even at an excessively high temperature of 80° C. as in a car in summer.
The term “Curie temperature”, as used herein, refers to a temperature at which the ferroelectricity of a material is lost. In general, the piezoelectric property of a piezoelectric material is also lost at the Curie temperature or higher. The Curie temperature may be determined by directly measuring the temperature at which ferroelectricity is lost or measuring the temperature at which the relative dielectric constant reaches its maximum in a very small alternating electric field.
A piezoelectric ceramic according to an embodiment of the present invention can maintain a tetragonal structure at a temperature in the range of −20° C. to 100° C., maintain a high mechanical quality factor, and avoid an orthorhombic crystal region in which the mechanical quality factor decreases. Thus, the piezoelectric ceramic can have a high and stable piezoelectric constant and a high and stable mechanical quality factor in a wide operating temperature range.
Crystal Grain Size
The average equivalent circular diameter of crystal grains of a piezoelectric ceramic according to an embodiment of the present invention is preferably 1 μm or more and 10 μm or less. Having an average equivalent circular diameter in this range, a piezoelectric ceramic according to an embodiment of the present invention can have satisfactory piezoelectric property and mechanical strength. An average equivalent circular diameter of less than 1 μm may result in a deterioration in piezoelectric property. An average equivalent circular diameter of more than 10 μm may result in a reduced mechanical strength. The average equivalent circular diameter is more preferably 1 μm or more and 4.7 μm or less.
In a piezoelectric ceramic according to an embodiment of the present invention, crystal grains having an equivalent circular diameter of 25 μm or less may constitute 99 percent by number or more of the crystal grains of the piezoelectric ceramic. When the percentage by number of the crystal grains having an equivalent circular diameter of 25 μm or less is in this range, the piezoelectric ceramic can have a satisfactory mechanical strength. The mechanical strength has a high negative correlation with the percentage of crystal grains having a large equivalent circular diameter. When the percentage by number of the crystal grains having an equivalent circular diameter of 25 μm or less is less than 99 percent by number, this results in an increase in crystal grains having an equivalent circular diameter of more than 25 μm, possibly resulting in a reduced mechanical strength.
The term “equivalent circular diameter”, as used herein, refers to a “projected area equivalent circular diameter” generally referred to in microscopy and refers to the diameter of a perfect circle having the same area as the projected area of a crystal grain. In the present invention, the equivalent circular diameter may be determined by any method. For example, the equivalent circular diameter may be determined by the image processing of an image of a surface of the piezoelectric ceramic taken with a polarizing microscope or a scanning electron microscope. Since the optimum magnification depends on the particle size to be measured, an optical microscope or an electron microscope may be selected in accordance with the particle size. The equivalent circular diameter may be determined from an image of a polished surface or a cross section rather than the ceramic surface.
Density of Piezoelectric Ceramic
A piezoelectric ceramic according to an embodiment of the present invention preferably has a relative density of 90% or more and 100% or less.
The relative density is the ratio of the measured density to the theoretical density, which is calculated from the lattice constant of the piezoelectric ceramic and the atomic weights of the constituent elements of the piezoelectric ceramic. The lattice constant can be measured by X-ray diffraction analysis. The density can be determined in accordance with Archimedes' principle.
A relative density of less than 90% may result in a deterioration in piezoelectric property, mechanical quality factor, or mechanical strength.
The lower limit of the relative density is more preferably 93% or more.
Method for Manufacturing Piezoelectric Ceramic
A method for manufacturing a piezoelectric ceramic according to an embodiment of the present invention will be described below.
Examples of Metallic Elements in Piezoelectric Ceramic
A method for manufacturing a piezoelectric ceramic according to an embodiment of the present invention includes sintering a compact containing Ba, Ca, Ti, Zr, Mn, and at least one metallic element selected from the group consisting of Cu, B, and Si at a temperature of 1200° C. or less. As described in detail below, a method for manufacturing a piezoelectric ceramic according to an embodiment of the present invention allows Ag, Pd, Au, Cu, Ni, or another metal that has a lower melting point and is more inexpensive than Pt and other noble metals, or an alloy thereof to be baked as an electrode on the piezoelectric ceramic. Thus, the method has industrially advantageous effects.
Raw Materials for Piezoelectric Ceramic
A common method for sintering an oxide, carbonate, nitrate, or oxalate solid powder containing the constituent elements of a piezoelectric ceramic at atmospheric pressure may be employed in the manufacture of the piezoelectric ceramic. The raw materials include a metallic compound, such as a Ba compound, a Ca compound, a Ti compound, a Zr compound, a Mn compound, a Cu compound, a B compound, and/or a Si compound.
Examples of the Ba compound include barium oxide, barium carbonate, barium oxalate, barium acetate, barium nitrate, barium titanate, barium zirconate, and barium zirconate titanate.
Examples of the Ca compound include calcium oxide, calcium carbonate, calcium oxalate, calcium acetate, calcium titanate, calcium zirconate, and calcium zirconate titanate.
Examples of the Ti compound include titanium oxide, barium titanate, barium zirconate titanate, and calcium titanate.
Examples of the Zr compound include zirconium oxide, barium zirconate, barium zirconate titanate, and calcium zirconate.
Examples of the Mn compound include manganese carbonate, manganese oxide, manganese dioxide, manganese acetate, and trimanganese tetroxide.
Examples of the Cu compound include copper(I) oxide, copper(II) oxide, copper carbonate, copper(II) acetate, and copper oxalate.
Examples of the B compound include boron trioxide.
Examples of the Si compound include silicon oxide.
A raw material for controlling the value a representing the ratio A/B of the number of moles of Ba and Ca at the A site to the number of moles of Ti and Zr at the B site of the piezoelectric ceramic according to an embodiment of the present invention is not particularly limited. A Ba compound, a Ca compound, a Ti compound, and a Zr compound have the same effect.
Granulated Powder and Compact
The term “compact”, as used herein, refers to a solid formed of a solid powder. A piezoelectric ceramic can be formed by firing a compact. The compact can be formed by uniaxial pressing, cold hydrostatic pressing, hot hydrostatic pressing, casting, or extrusion molding. The compact may be formed using a granulated powder. Sintering of a compact formed of a granulated powder has an advantage that the grain size distribution of the sintered body tends to become uniform.
The raw material powder of a piezoelectric ceramic according to an embodiment of the present invention may be granulated by any method. Spray drying can make the particle size of the granulated powder more uniform.
A binder for use in granulation may be poly(vinyl alcohol) (PVA), poly(vinyl butyral) (PVB), or an acrylic resin. The amount of binder is preferably in the range of 1 part by weight to 10 parts by weight per 100 parts by weight of the raw material powder of the piezoelectric ceramic, more preferably 2 parts by weight to 5 parts by weight in order to increase the density of the compact.
Sintering of Compact
In the present invention, a compact may be sintered by any method.
Examples of the sintering method include sintering in an electric furnace, sintering in a gas furnace, electric heating, microwave sintering, millimeter-wave sintering, and hot isostatic pressing (HIP). Sintering in an electric furnace or a gas furnace may be performed in a continuous furnace or a batch furnace.
The sintering temperature of the ceramic by the sintering method is 1200° C. or less. A homogeneous piezoelectric ceramic can be manufactured at a sintering temperature of 1200° C. or less. A sintering temperature of more than 1200° C. may result in the aggregation of the second auxiliary component and adversely affect the mechanical strength of the piezoelectric ceramic. The lower limit of the sintering temperature is not particularly limited and may be a temperature above which the compounds can react and crystals can grow sufficiently. The sintering temperature is preferably 1000° C. or more and 1200° C. or less, more preferably 1100° C. or more and 1200° C. or less, such that the ceramic grain size is in the range of 1 to 10 μm. A piezoelectric ceramic sintered in the temperature range described above has satisfactory piezoelectric performance.
In order to ensure the reproducibility and stability of the characteristics of a piezoelectric ceramic manufactured by sintering, sintering may be performed at a constant temperature within the range described above for two hours or more and 24 hours or less. Two-step sintering may be performed.
A piezoelectric ceramic manufactured by sintering may be polished and then heat-treated at a temperature of 1000° C. or more. Heat treatment of the piezoelectric ceramic at a temperature of 1000° C. or more can relieve the residual stress of the piezoelectric ceramic resulting from mechanically polishing and thereby improves the piezoelectric property of the piezoelectric ceramic. Heat treatment of the piezoelectric ceramic can also remove the raw material powder, such as barium carbonate, precipitated at grain boundaries. The heat-treatment time may be, but is not limited to, one hour or more.
Electrode
FIG. 1 is a schematic view of a piezoelectric element according to an embodiment of the present invention. The piezoelectric element includes a first electrode 1, a piezoelectric ceramic 2, and a second electrode 3. The piezoelectric ceramic 2 is a piezoelectric ceramic according to an embodiment of the present invention.
The first electrode 1 and the second electrode 3 are placed on the piezoelectric ceramic 2 to form the piezoelectric element, thereby allowing the evaluation of the piezoelectric property of the piezoelectric ceramic 2. Each of the first electrode 1 and the second electrode 3 has a thickness in the range of approximately 5 to 2000 nm and is made of an electroconductive material. The electroconductive material is not particularly limited and may be any material that is commonly used for piezoelectric elements. Examples of the electroconductive material include metals, such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu, and compounds thereof.
Each of the first electrode 1 and the second electrode 3 may be made of the electroconductive material alone or may be a multilayer made of two or more of the electroconductive materials. The material(s) of the first electrode 1 may be different from the material(s) of the second electrode 3.
The first electrode 1 and the second electrode 3 may be manufactured by any method, for example, by baking of a metal paste, sputtering, or vapor deposition. The first electrode 1 and the second electrode 3 may have a desired patter.
Polarization Treatment
The piezoelectric element may have a unidirectional spontaneous polarization axis. Having the unidirectional spontaneous polarization axis can increase the piezoelectric constant of the piezoelectric element.
The polarization method for the piezoelectric element is not particularly limited. Polarization treatment may be performed in the atmosphere or in a silicone oil. The polarization temperature may be in the range of 60° C. to 150° C. The optimum conditions for polarization may vary with the composition of the piezoelectric ceramic of the piezoelectric element. The electric field applied in polarization treatment may be in the range of 800 V/mm to 2.0 kV/mm.
Method for Measuring Mechanical Quality Factor
The piezoelectric constant and the mechanical quality factor of the piezoelectric element can be calculated from the resonance frequency and the antiresonant frequency measured with a commercially available impedance analyzer in accordance with the Standard of Electronic Materials Manufacturers Association of Japan (JEITA EM-4501). This method is hereinafter referred to as a resonance-antiresonance method.
Structure of Multilayered Piezoelectric Element
A multilayered piezoelectric element manufactured using a piezoelectric ceramic according to an embodiment of the present invention will be described below.
A multilayered piezoelectric element according to an embodiment of the present invention includes piezoelectric ceramic layers and electrode layers alternately stacked on top of one another. The electrode layers include an internal electrode. The piezoelectric ceramic layers are formed of a piezoelectric ceramic according to an embodiment of the present invention.
FIG. 2A is a schematic cross-sectional view of a multilayered piezoelectric element according to an embodiment of the present invention. The multilayered piezoelectric element includes piezoelectric ceramic layers 54 and electrode layers alternately stacked on top of one another. The electrode layers include an internal electrode 55. The piezoelectric ceramic layers 54 are formed of a piezoelectric ceramic according to an embodiment of the present invention. The electrode layers may include external electrodes, such as a first electrode 51 and a second electrode 53, as well as the internal electrode 55.
The multilayered piezoelectric element illustrated in FIG. 2A includes two piezoelectric ceramic layers 54 and one internal electrode 55 interposed therebetween, and the multilayered structure is disposed between the first electrode 51 and the second electrode 53. The number of piezoelectric ceramic layers and the number of internal electrodes are not particularly limited and may be increased, as illustrated in FIG. 2B. The multilayered piezoelectric element illustrated in FIG. 2B includes nine piezoelectric ceramic layers 504 and eight internal electrodes 505 alternately stacked on top of one another, and the multilayered structure is disposed between a first electrode 501 and a second electrode 503. The multilayered piezoelectric element further includes an external electrode 506a and an external electrode 506b for connecting the internal electrodes 505 to each other.
The size and shape of the internal electrodes 505 and the external electrodes 506a and 506b may be different from the size and shape of the piezoelectric ceramic layers 504. Each of the internal electrodes 505 and the external electrodes 506a and 506b may be composed of a plurality of portions.
Each of the internal electrodes 55 and 505 and the external electrodes 506a and 506b has a thickness in the range of approximately 5 to 2000 nm and is made of an electroconductive material. The electroconductive material is not particularly limited and may be any material that is commonly used for piezoelectric elements. Examples of the electroconductive material include metals, such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu, and compounds thereof. Each of the internal electrodes 55 and 505 and the external electrodes 506a and 506b may be made of the electroconductive material alone or a mixture or an alloy of the electroconductive materials or may be a multilayer made of two or more of the electroconductive materials. The internal electrodes 55 and 505 and the external electrodes 506a and 506b may be made of different materials.
A multilayered piezoelectric element according to an embodiment of the present invention includes an internal electrode containing Ag and Pd. The weight ratio M1/M2 of the weight M1 of Ag to the weight M2 of Pd is preferably in the range of 0.25≦M1/M2≦4.0. A weight ratio M1/M2 of less than 0.25 is undesirable because of a high sintering temperature of the internal electrode. A weight ratio M1/M2 of more than 4.0 is also undesirable because the internal electrode has an island structure and a heterogeneous surface. The weight ratio M1/M2 is more preferably in the range of 2.3≦M1/M2≦3.0.
The internal electrodes 55 and 505 may contain at least one of Ni and Cu, which are inexpensive electrode materials. When the internal electrodes 55 and 505 contain at least one of Ni and Cu, the multilayered piezoelectric element may be baked in a reducing atmosphere.
As illustrated in FIG. 2B, the plurality of electrodes including the internal electrodes 505 may be connected to each other in order to synchronize the driving voltage phases. For example, internal electrodes 505a may be connected to the first electrode 501 through the external electrode 506a. Internal electrodes 505b may be connected to the second electrode 503 through the external electrode 506b. The internal electrodes 505a and the internal electrodes 505b may be alternately disposed. The electrodes may be connected by any method. For example, an electrode or an electric wire for connection may be disposed on a side surface of the multilayered piezoelectric element, or a through hole passing through the piezoelectric ceramic layers 504 may be formed and coated with an electroconductive material to connect the electrodes.
Method for Manufacturing Multilayered Piezoelectric Element
A method for manufacturing a multilayered piezoelectric element using a piezoelectric ceramic according to an embodiment of the present invention will be described below.
A method for manufacturing a multilayered piezoelectric element according to an embodiment of the present invention includes (A) preparing a slurry of a metallic compound powder containing at least Ba, Ca, Ti, Zr, and Mn and at least one second auxiliary component or element selected from the group consisting of Cu, B, and Si, (B) forming a compact from the slurry, (C) forming an electrode on the compact, and (D) sintering a plurality of the compacts at a temperature of 1200° C. or less to manufacture the multilayered piezoelectric element.
The metallic compound powder used in (A) may be a powder of a Ba compound, a Ca compound, a Ti compound, a Zr compound, and/or a Mn compound. Examples of the Ba compound include barium oxide, barium carbonate, barium oxalate, barium acetate, barium nitrate, barium titanate, barium zirconate, and barium zirconate titanate.
Examples of the Ca compound include calcium oxide, calcium carbonate, calcium oxalate, calcium acetate, calcium titanate, calcium zirconate, and calcium zirconate titanate.
Examples of the Ti compound include titanium oxide, barium titanate, barium zirconate titanate, and calcium titanate.
Examples of the Zr compound include zirconium oxide, barium zirconate, barium zirconate titanate, and calcium zirconate.
Examples of the Mn compound include manganese carbonate, manganese oxide, manganese dioxide, manganese acetate, and trimanganese tetroxide.
Examples of the Cu compound include copper(I) oxide, copper(II) oxide, copper carbonate, copper(II) acetate, and copper oxalate.
Examples of the B compound include boron trioxide.
Examples of the Si compound include silicon oxide.
An exemplary method for preparing the slurry in (A) will be described below. The metallic compound powder is mixed with a solvent. The weight of the solvent is 1.6 to 1.7 times the weight of the metallic compound powder. The solvent may be toluene, ethanol, a mixed solvent of toluene and ethanol, n-butyl acetate, or water. After mixing in a ball mill for 24 hours, a binder and a plasticizer are added to the mixture. The binder may be poly(vinyl alcohol) (PVA), poly(vinyl butyral) (PVB), or an acrylic resin. When the binder is PVB, the weight ratio of the solvent to PVB may be 88:12. The plasticizer may be dioctyl sebacate, dioctyl phthalate, dibutyl phthalate, or an ammonium carboxylate. When the plasticizer is dibutyl phthalate, the weight of dibutyl phthalate is the same as the weight of the binder. The mixture is again mixed in the ball mill overnight. The amount of solvent or binder is controlled such that the slurry viscosity is in the range of 300 to 500 mPa·s.
The compact in (B) is a sheet of the mixture of the metallic compound powder, the binder, and the plasticizer. The compact in (B) may be formed by a sheet forming method. The sheet forming method may be a doctor blade method. In accordance with the doctor blade method, the slurry is applied to a substrate with a doctor blade and is dried to form a sheet of the compact. The substrate may be a poly(ethylene terephthalate) (PET) film. A surface of the PET film on which the slurry is to be applied may be coated with a fluorine compound in order to facilitate the removal of the compact. The slurry may be dried by natural drying or hot-air drying. The thickness of the compact is not particularly limited and may be adjusted to the thickness of the multilayered piezoelectric element. The thickness of the compact can be increased with increasing viscosity of the slurry.
The electrode in (C), more specifically, an internal electrode 5 or an external electrode may be manufactured by any method, for example, baking of a metal paste, sputtering, vapor deposition, or printing. In order to reduce the driving voltage, the thickness and the intervals of piezoelectric ceramic layers 4 may be reduced. In such a case, a multilayered body containing precursors of the piezoelectric ceramic layers 4 and the internal electrodes 5 is fired. The material of the internal electrodes 5 should not change its shape or cause a deterioration in electrical conductivity at the sintering temperature of the piezoelectric ceramic layers 4. The sintering temperature of the piezoelectric ceramic is in the range of 1100° C. to 1200° C., which is lower than the sintering temperature of conventional barium titanate piezoelectric ceramics. Thus, a metal that has a lower melting point and is more inexpensive than Pt, such as Ag, Pd, Au, Cu, or Ni, or an alloy thereof may be used for the internal electrodes 5 and external electrodes 6a and 6b. The external electrodes 6a and 6b may be formed after firing the multilayered body. In this case, the external electrodes 6a and 6b may be made of Al or a carbonaceous electrode material, as well as Ag, Pd, Cu, or Ni.
These electrodes may be formed by screen printing. In accordance with screen printing, a metal paste is applied to the compact disposed on a substrate through a screen printing plate using a blade. The screen printing plate has a screen mesh. The metal paste is applied to the compact through the screen mesh. The screen mesh of the screen printing plate may have a pattern. The pattern can be transferred to the compact using the metal paste, thereby patterning an electrode on the compact.
After the electrode is formed in (C), one or a plurality of compacts removed from the substrate are stacked and press-bonded, for example, by uniaxial pressing, cold hydrostatic pressing, or hot hydrostatic pressing. Hot hydrostatic pressing can apply isotropically uniform pressure. Heating the compacts to approximately the glass transition point of the binder can enhance press bonding. A plurality of compacts can be press-bonded in order to achieve the desired thickness.
For example, 10 to 100 layers of the compacts can be heat-pressed at a temperature in the range of 50° C. to 80° C. at a pressure in the range of 10 to 60 MPa for 10 seconds to 10 minutes. The electrodes may have an alignment mark in order to accurately stack the compacts. The compacts may have a positioning through hole in order to accurately stack the compacts.
The sintering temperature of 1200° C. or less in (D) allows the use of a metal that has a lower melting point and is more inexpensive than Pt, such as Ag, Pd, Au, Cu, or Ni, or an alloy thereof.
In a method for manufacturing a multilayered piezoelectric element according to an embodiment of the present invention, the slurry may contain a perovskite metal oxide containing at least one of Ba and Ca and at least one of Ti and Zr. Examples of the perovskite metal oxide include barium titanate, barium zirconate, barium zirconate titanate, calcium titanate, calcium zirconate, and calcium zirconate titanate.
When the slurry contains the perovskite metal oxide, this advantageously promotes grain growth and increases the density of the compact.
Liquid Discharge Head
A liquid discharge head including a piezoelectric element according to an embodiment of the present invention will be described below. A liquid discharge head according to an embodiment of the present invention includes a liquid chamber and a discharge port in communication with the liquid chamber. The liquid chamber has a vibrating unit that includes a piezoelectric element or a multilayered piezoelectric element according to an embodiment of the present invention.
FIG. 3A is a schematic cross-sectional view of a liquid discharge head according to an embodiment of the present invention, and FIG. 3B is a schematic perspective view of the liquid discharge head illustrated in FIG. 3A. As illustrated in FIGS. 3A and 3B, the liquid discharge head includes a piezoelectric element 101 according to an embodiment of the present invention. The piezoelectric element 101 includes a first electrode 1011, a piezoelectric ceramic 1012, and a second electrode 1013. As illustrated in FIG. 3B, the piezoelectric ceramic 1012 may be patterned.
FIG. 3B is a schematic perspective view of the liquid discharge head illustrated in FIG. 3A. The liquid discharge head includes a discharge port 105, an individual liquid chamber 102, a communicating hole 106 that connects the individual liquid chamber 102 to the discharge port 105, a liquid chamber partition wall 104, a common liquid chamber 107, a diaphragm 103, and the piezoelectric element 101. Although the piezoelectric element 101 is rectangular in FIG. 3B, the piezoelectric element 101 may be of another shape, such as elliptical, circular, or parallelogrammic. In general, the piezoelectric ceramic 1012 has a shape similar to the shape of the individual liquid chamber 102.
The piezoelectric element 101 of the liquid discharge head will be described in detail below with reference to FIG. 3A. FIG. 3A is a cross-sectional view of FIG. 3B in the width direction of the piezoelectric element. Although the piezoelectric element 101 has a rectangular cross section in FIG. 3A, the piezoelectric element 101 may have a trapezoidal or inverted trapezoidal cross section.
In FIG. 3A, the first electrode 1011 is a lower electrode, and the second electrode 1013 is an upper electrode. The first electrode 1011 and the second electrode 1013 may be arranged differently. For example, the first electrode 1011 may be a lower electrode or an upper electrode. Likewise, the second electrode 1013 may be an upper electrode or a lower electrode. A buffer layer 108 may be disposed between the diaphragm 103 and the lower electrode. These different designations result from variations in the method for manufacturing the device, and each of the cases has the advantages of the present invention.
In the liquid discharge head, the diaphragm 103 bends upward and downward with the expansion and contraction of the piezoelectric ceramic 1012, thereby applying pressure to a liquid in the individual liquid chamber 102. This allows the liquid to be discharged from the discharge port 105. A liquid discharge head according to an embodiment of the present invention can be used in printers and in the manufacture of electronic devices.
The thickness of the diaphragm 103 is 1.0 μm or more and 15 μm or less, preferably 1.5 μm or more and 8 μm or less. The diaphragm 103 may be made of any material, for example, Si. The diaphragm 103 made of Si may be doped with boron or phosphorus. The buffer layer 108 and the first electrode 1011 on the diaphragm 103 may serve as part of a diaphragm. The buffer layer 108 has a thickness of 5 nm or more and 300 nm or less, preferably 10 nm or more and 200 nm or less. The discharge port 105 has an equivalent circular diameter of 5 μm or more and 40 μm or less. The discharge port 105 may be circular, star-shaped, square, or triangular.
Liquid Discharge Apparatus
A liquid discharge apparatus according to an embodiment of the present invention will be described below. The liquid discharge apparatus includes a recording medium conveying unit and the liquid discharge head described above. The liquid discharge apparatus may be an ink jet recording apparatus, as illustrated in FIGS. 4 and 5. FIG. 5 illustrates the liquid discharge apparatus (ink jet recording apparatus) 881 illustrated in FIG. 4 without exteriors 882 to 885 and 887. The ink jet recording apparatus 881 includes an automatic feeder 897 for automatically feeding a recording paper sheet as a recording medium to the main body 896 of the apparatus. The ink jet recording apparatus 881 further includes a conveying unit 899 for conveying a recording paper sheet from the automatic feeder 897 to a predetermined recording position and from the recording position to an outlet 898, a recording unit 891 for recording to the recording paper at the recording position, and a recovering unit 890 for recovering the recording unit 891. The recording unit 891 includes a carriage 892 for housing a liquid discharge head according to an embodiment of the present invention. The carriage 892 travels along a rail.
The carriage 892 travels along a rail in response to electric signals sent from a computer. Upon the application of a driving voltage to electrodes disposed on a piezoelectric ceramic, the piezoelectric ceramic is deformed. Upon the deformation, the piezoelectric ceramic presses the individual liquid chamber 102 via the diaphragm 103 illustrated in FIG. 3B, thereby discharging an ink from the discharge port 105 to print characters.
A liquid discharge apparatus according to an embodiment of the present invention can uniformly discharge a liquid at a high speed and can be reduced in size.
In addition to the printer described above, a liquid discharge apparatus according to an embodiment of the present invention can be used in other ink jet recording apparatuses, such as facsimile machines, multifunction devices, and copying machines, and industrial liquid discharge apparatuses.
Ultrasonic Motor
An ultrasonic motor according to an embodiment of the present invention includes a vibrating member and a moving body in contact with the vibrating member. The vibrating member includes a piezoelectric element or a multilayered piezoelectric element according to an embodiment of the present invention.
FIGS. 6A and 6B are schematic views of ultrasonic motors according to embodiments of the present invention. The ultrasonic motor illustrated in FIG. 6A includes a single plate of a piezoelectric element according to an embodiment of the present invention. The ultrasonic motor includes an oscillator 201, a rotor 202 pressed against a sliding surface of the oscillator 201 by the action of a pressure spring (not shown), and an output shaft 203, which is formed integrally with the rotor 202. The oscillator 201 includes a metal elastic ring 2011, a piezoelectric element 2012 according to an embodiment of the present invention, and an organic adhesive 2013 (epoxy or cyanoacrylate) that bonds the piezoelectric element 2012 to the elastic ring 2011. Although not shown in the figure, the piezoelectric element 2012 includes a piezoelectric ceramic between a first electrode and a second electrode.
Upon the application of two-phase alternating voltages that differ by an odd number times π/4 in phase to a piezoelectric element according to an embodiment of the present invention, a flexural traveling wave occurs in the oscillator 201, and points on the sliding surface of the oscillator 201 go through elliptical motion. The rotor 202 pressed against the sliding surface of the oscillator 201 receives friction force from the oscillator 201 and rotates in a direction opposite to the direction of the flexural traveling wave. A body to be driven (not shown) joined to the output shaft 203 is driven by the rotational force of the rotor 202.
Upon the application of a voltage to a piezoelectric ceramic, the piezoelectric ceramic expands and contracts because of the transverse piezoelectric effect. An elastic body, such as a metal, joined to the piezoelectric element is bent with the expansion and contraction of the piezoelectric ceramic. The ultrasonic motor described herein utilizes this principle.
FIG. 6B illustrates an ultrasonic motor that includes a multilayered piezoelectric element. The oscillator 204 includes a multilayered piezoelectric element 2042 in a tubular metal elastic body 2041. The multilayered piezoelectric element 2042 includes a plurality of layered piezoelectric ceramics (not shown) and includes a first electrode and a second electrode on the outer surfaces of the layered piezoelectric ceramics and internal electrodes within the layered piezoelectric ceramics. The metal elastic body 2041 is fastened with a bolt to hold the piezoelectric element 2042, thereby constituting the oscillator 204.
Upon the application of alternating voltages of different phases to the piezoelectric element 2042, the oscillator 204 causes two oscillations perpendicular to each other. The two oscillations are synthesized to form a circular oscillation for driving the tip of the oscillator 204. The oscillator 204 has an annular groove at its upper portion. The annular groove increases the oscillatory displacement for driving.
A rotor 205 is pressed against the oscillator 204 by the action of a pressure spring 206 and receives friction force for driving. The rotor 205 is rotatably supported by a bearing.
Optical Apparatus
An optical apparatus according to an embodiment of the present invention will be described below. The optical apparatus includes the ultrasonic motor described above in a drive unit.
FIGS. 7A and 7B are cross-sectional views of an interchangeable lens barrel of a single-lens reflex camera, which is an image pickup apparatus according to an embodiment of the present invention. FIG. 8 is an exploded perspective view of an interchangeable lens barrel of a single-lens reflex camera, which is an image pickup apparatus according to an embodiment of the present invention. A fixed barrel 712, a linear guide barrel 713, and a front lens group barrel 714 are fixed to a removable mount 711 of the camera. These components are fixed members of the interchangeable lens barrel.
The linear guide barrel 713 has a linear guide groove 713a for a focus lens 702 in the optical axis direction. The focus lens 702 is supported by a rear lens group barrel 716. Cam rollers 717a and 717b protruding outwardly in the radial direction are fixed to the rear lens group barrel 716 with a screw 718. The cam roller 717a fits in the linear guide groove 713a. 
A cam ring 715 rotatably fits in the internal circumference of the linear guide barrel 713. A roller 719 fixed to the cam ring 715 is caught in an annular groove 713b of the linear guide barrel 713, thereby restricting the relative displacement of the linear guide barrel 713 and the cam ring 715 in the optical axis direction. The cam ring 715 has a cam groove 715a for the focus lens 702. The cam roller 717b also fits in the cam groove 715a. 
A rotation transmitting ring 720 is rotatably held by a ball race 727 at a fixed position on the periphery of the fixed barrel 712. A driven roller 722 is rotatably held by a shaft 720f extending radially from the rotation transmitting ring 720. A large-diameter portion 722a of the driven roller 722 is in contact with a mount side end face 724b of a manual focus ring 724. A small-diameter portion 722b of the driven roller 722 is in contact with a joint 729. Six driven rollers 722 are disposed at regular intervals on the periphery of the rotation transmitting ring 720. Each of the driven rollers 722 satisfies the structural relationship described above.
A low-friction sheet (washer member) 733 is disposed on the inside of the manual focus ring 724. The low-friction sheet 733 is disposed between a mount side end face 712a of the fixed barrel 712 and a front end face 724a of the manual focus ring 724. The low-friction sheet 733 has a circular outer surface having a diameter that fits to the inner diameter 724c of the manual focus ring 724. The inner diameter 724c of the manual focus ring 724 fits to the diameter of an outer portion 712b of the fixed barrel 712. The low-friction sheet 733 can reduce friction in the rotating ring mechanism in which the manual focus ring 724 rotates about the optical axis relative to the fixed barrel 712. The large-diameter portion 722a of the driven roller 722 is pressed against the mount side end face 724b of the manual focus ring 724 because the wave washer 726 presses the ultrasonic motor 725 forward to the front of the lens. Likewise, because the wave washer 726 presses the ultrasonic motor 725 forward to the front of the lens, the small-diameter portion 722b of the driven roller 722 is pressed against the joint 729. The wave washer 726 is prevented from moving toward the mount by a washer 732 bayonet coupled to the fixed barrel 712. The spring force (impellent force) of the wave washer 726 is transmitted to the ultrasonic motor 725 and the driven roller 722 and furthermore presses the manual focus ring 724 against the mount side end face 712a of the fixed barrel 712. In other words, the manual focus ring 724 is pressed against the mount side end face 712a of the fixed barrel 712 via the low-friction sheet 733. Thus, when the ultrasonic motor 725 is rotated by a control unit (not shown) relative to the fixed barrel 712, the driven roller 722 rotates about the shaft 720f because the joint 729 is in frictional contact with the small-diameter portion 722b of the driven roller 722. The rotation of the driven roller 722 about the shaft 720f causes the rotation of the rotation transmitting ring 720 about the optical axis (automatic focusing).
When a manual input unit (not shown) provides the manual focus ring 724 with rotational force about the optical axis, since the mount side end face 724b of the manual focus ring 724 is pressed against the large-diameter portion 722a of the driven roller 722, the driven roller 722 is rotated about the shaft 720f because of friction force. The rotation of the large-diameter portion 722a of the driven roller 722 about the shaft 720f causes the rotation of the rotation transmitting ring 720 about the optical axis. However, the ultrasonic motor 725 is not rotated because of the friction force between a rotor 725c and a stator 725b (manual focusing). The rotation transmitting ring 720 is provided with two focus keys 728 facing each other. These focus keys 728 fit into notches 715b at the tip of the cam ring 715. Upon automatic focusing or manual focusing, the rotation transmitting ring 720 is rotated about the optical axis, and the rotational force is transmitted to the cam ring 715 via the focus keys 728. When the cam ring 715 is rotated about the optical axis, the cam roller 717b moves the cam roller 717a and the rear lens group barrel 716 restricted by the linear guide groove 713a forward or backward along the cam groove 715a of the cam ring 715. This drives the focus lens 702 and allows focusing.
Although an optical apparatus according to an embodiment of the present invention has been described with reference to an interchangeable lens barrel of a single-lens reflex camera, the optical apparatus may also be applied to optical apparatuses that include an ultrasonic motor in a drive unit, for example, cameras, such as compact cameras and electronic still cameras.
Vibratory Apparatus and Dust Removing Device
Vibratory apparatuses for conveying or removing particles, powders, and liquids are widely used in electronic devices.
As an example of a vibratory apparatus according to the present invention, the vibratory apparatus includes a piezoelectric element according to an embodiment of the present invention will be described below.
A dust removing device according to an embodiment of the present invention includes a vibrating member that includes a piezoelectric element or a multilayered piezoelectric element according to an embodiment of the present invention.
FIGS. 9A and 9B are schematic views of a dust removing device 310 according to an embodiment of the present invention. The dust removing device 310 includes a plate of the piezoelectric element 330 and the diaphragm 320. The piezoelectric element 330 may be a multilayered piezoelectric element according to an embodiment of the present invention. The diaphragm 320 may be made of any material. When the dust removing device 310 is used in optical devices, the diaphragm 320 may be made of a translucent or transparent material or a light reflective material.
FIGS. 10A to 10C are schematic views of the piezoelectric element 330 illustrated in FIGS. 9A and 9B. FIGS. 10A and 10C illustrate the front and back sides of the piezoelectric element 330. FIG. 10B is a side view of the piezoelectric element 330. As illustrated in FIG. 10A to 10C, the piezoelectric element 330 includes a piezoelectric ceramic 331, a first electrode 332, and a second electrode 333. The first electrode 332 and the second electrode 333 are disposed on opposite sides of the piezoelectric ceramic 331. As in FIGS. 9A and 9B, the piezoelectric element 330 may be a multilayered piezoelectric element according to an embodiment of the present invention. In this case, the piezoelectric ceramic 331 includes piezoelectric ceramic layers and internal electrodes alternately stacked on top of one another. The internal electrodes are alternately connected to the first electrode 332 and the second electrode 333, thereby allowing the piezoelectric ceramic layers to alternately have a drive waveform of a different phase. As illustrated in FIG. 10C, a surface of the piezoelectric element 330 on which the first electrode 332 is disposed is referred to as a first electrode surface 336. As illustrated in FIG. 10A, a surface of the piezoelectric element 330 on which the second electrode 332 is disposed is referred to as a second electrode surface 337.
The term “electrode surface”, as used herein, refers to a surface of a piezoelectric element on which an electrode is disposed. For example, as illustrated in FIG. 10B, the first electrode 332 may round a corner and extends to the second electrode surface 337.
As illustrated in FIGS. 9A and 9B, the first electrode surface 336 of the piezoelectric element 330 is bonded to the diaphragm 320. Actuation of the piezoelectric element 330 produces a stress between the piezoelectric element 330 and the diaphragm 320, causing out-of-plane oscillations on the diaphragm 320. The dust removing device 310 removes foreign substances, such as dust, on the diaphragm 320 by the action of out-of-plane oscillations. The term “out-of-plane oscillations”, as used herein, refers to elastic oscillations that cause displacements of a diaphragm in the optical axis direction or the diaphragm thickness direction.
FIGS. 11A and 11B are schematic views illustrating the vibration principle of the dust removing device 310. In FIG. 11A, an in-phase alternating electric field is applied to a left-and-right pair of the piezoelectric elements 330 to cause out-of-plane oscillations of the diaphragm 320. The direction of polarization of the piezoelectric ceramic constituting the left-and-right pair of the piezoelectric elements 330 is the same as the thickness direction of the piezoelectric elements 330. The dust removing device 310 is driven in a seventh oscillation mode. In FIG. 11B, an anti-phase alternating voltage is applied to a left-and-right pair of the piezoelectric elements 330 to cause out-of-plane oscillations of the diaphragm 320. The dust removing device 310 is driven in a sixth oscillation mode. The dust removing device 310 can employ at least two oscillation modes to effectively remove dust on the surface of the diaphragm.
Image Pickup Apparatus
An image pickup apparatus according to an embodiment of the present invention will be described below. An image pickup apparatus according to an embodiment of the present invention includes a dust removing device according to an embodiment of the present invention and an image pickup element unit, wherein the dust removing device includes a vibrating member on the light incident side of the image pickup element unit. FIGS. 12 and 13 illustrate a digital single-lens reflex camera, which is an image pickup apparatus according to an embodiment of the present invention.
FIG. 12 is a front perspective view of the main body 601 of the camera viewed from the object side. An imaging lens unit has been removed. FIG. 13 is an exploded perspective view of the inside of the camera, illustrating surrounding structures of a dust removing device according to an embodiment of the present invention and an image pickup unit 400.
The main body 601 of the camera includes a mirror box 605 to which an image light beam passing through an imaging lens is directed. The mirror box 605 includes a main mirror (quick return mirror) 606. The main mirror 606 can make an angle of 45 degrees with the optical axis to direct an image light beam to a penta roof mirror (not shown) or may avoid the image light beam in order to direct the image light beam to an image pickup element (not shown).
The mirror box 605 and a shutter unit 200 are disposed in front of a main body chassis 300 of the main body 601 of the camera in this order from the object side. The image pickup unit 400 is disposed on the photographer side of the main body chassis 300. The image pickup unit 400 is installed such that an image pickup area of the image pickup element is disposed at a predetermined distance from and parallel to the surface of a mount 602 to which an imaging lens unit is to be attached.
Although the digital single-lens reflex camera has been described as an image pickup apparatus according to an embodiment of the present invention, the image pickup apparatus may be an interchangeable-lens camera, such as a mirrorless digital interchangeable-lens camera without the mirror box 605. Among various image pickup apparatuses and electrical and electronic devices that include image pickup apparatuses, such as interchangeable-lens video cameras, copying machines, facsimile machines, and scanners, an image pickup apparatus according to an embodiment of the present invention can particularly be applied to devices that require the removal of dust deposited on a surface of an optical component.
Electronic Device
An electronic device according to an embodiment of the present invention will be described below. The electronic device includes a piezoelectric acoustic component that includes a piezoelectric element or a multilayered piezoelectric element according to an embodiment of the present invention. The piezoelectric acoustic component may be a loudspeaker, a buzzer, a microphone, or a surface acoustic wave (SAW) device.
FIG. 14 is a perspective view of the main body 931 of a digital camera, which is an electronic device according to an embodiment of the present invention. An optical device 901, a microphone 914, an electronic flash unit 909, and a fill light unit 916 are disposed on the front surface of the main body 931. The microphone 914 is disposed within the main body and is indicated by a broken line. An opening for catching external sound is disposed in front of the microphone 914.
A power switch 933, a loudspeaker 912, a zoom lever 932, and a release button 908 for focusing are disposed on the top surface of the main body 931. The loudspeaker 912 is disposed within the main body 931 and is indicated by a broken line. An opening for transmitting sound to the outside is disposed in front of the loudspeaker 912.
The piezoelectric acoustic component may be used in at least one of the microphone 914, the loudspeaker 912, and a surface acoustic wave device.
Although the digital camera has been described as an electronic device according to an embodiment of the present invention, the electronic device may also be applied to various electronic devices that include a piezoelectric acoustic component, such as audio-reproducing devices, audio-recording devices, mobile phones, and information terminals.
As described above, a piezoelectric element and a multilayered piezoelectric element according to an embodiment of the present invention are suitable for liquid discharge heads, liquid discharge apparatuses, ultrasonic motors, optical apparatuses, vibratory apparatuses, dust removing devices, image pickup apparatuses, and electronic devices.
A liquid discharge head manufactured by using a lead-free piezoelectric ceramic according to an embodiment of the present invention can have a nozzle density and a discharge velocity higher than or equal to those of liquid discharge heads manufactured by using a lead-containing piezoelectric ceramic.
A liquid discharge apparatus manufactured by using a lead-free piezoelectric ceramic according to an embodiment of the present invention can have a discharge velocity and discharge accuracy higher than or equal to those of liquid discharge apparatuses manufactured by using a lead-containing piezoelectric ceramic.
An ultrasonic motor manufactured by using a lead-free piezoelectric ceramic according to an embodiment of the present invention can have driving force and durability higher than or equal to those of ultrasonic motors manufactured by using a lead-containing piezoelectric ceramic.
An optical apparatus manufactured by using a lead-free piezoelectric ceramic according to an embodiment of the present invention can have durability and operation accuracy higher than or equal to those of optical apparatuses manufactured by using a lead-containing piezoelectric ceramic.
A vibratory apparatus manufactured by using a lead-free piezoelectric ceramic according to an embodiment of the present invention can have oscillation capability and durability higher than or equal to those of vibratory apparatuses manufactured by using a lead-containing piezoelectric ceramic.
A dust removing device manufactured by using a lead-free piezoelectric ceramic according to an embodiment of the present invention can have dust removal efficiency and durability higher than or equal to those of dust removing devices manufactured by using a lead-containing piezoelectric ceramic.
An image pickup apparatus manufactured by using a lead-free piezoelectric ceramic according to an embodiment of the present invention can have a dust removal function higher than or equal to those of image pickup apparatuses manufactured by using a lead-containing piezoelectric ceramic.
A piezoelectric acoustic component manufactured by using a lead-free piezoelectric ceramic according to an embodiment of the present invention can be used to provide an electronic device that has sound production ability higher than or equal to those of electronic devices manufactured by using a lead-containing piezoelectric ceramic.
A piezoelectric ceramic according to an embodiment of the present invention may be used in ultrasonic transducers, piezoelectric actuators, piezoelectric sensors, and ferroelectric memories, as well as liquid discharge heads and motors.
EXAMPLES
Although the present invention is further described in the following examples, the present invention is not limited to these examples.
A piezoelectric ceramic according to an example of the present invention was manufactured.
Piezoelectric Ceramic
Example 1
A composition (Ba0.870Ca0.130)1.0111(Ti0.970Zr0.030)O3 was weighed as described below. This composition is represented by the general formula (Ba1-xCax)a(Ti1-yZry)O3, wherein x=0.130, y=0.030, and a=1.0111.
Barium titanate having an average particle diameter of 100 nm (BT-01, manufactured by Sakai Chemical Industry Co., Ltd.), calcium titanate having an average particle diameter of 300 nm (CT-03, manufactured by Sakai Chemical Industry Co., Ltd.), and calcium zirconate having an average particle diameter of 300 nm (CZ-03, manufactured by Sakai Chemical Industry Co., Ltd.) were weighed as the raw materials of the main component such that Ba, Ca, Ti, and Zr satisfied the composition (Ba0.870Ca0.130)1.0111(Ti0.970Zr0.030)O3. The value a representing the ratio of the number of moles of Ba and Ca at the A site to the number of moles of Ti and Zr at the B site was controlled with barium oxalate and calcium oxalate.
Manganese dioxide was weighed such that the b mol of the first auxiliary component Mn was 0.0121 mol per mole of the composition (Ba0.870Ca0.130)1.0111(Ti0.970Zr0.030)O3.
Silicon dioxide and boron trioxide were weighed such that the second auxiliary components Si and B were 0.0140 parts by weight and 0.0066 parts by weight on a metal basis, respectively, per 100 parts by weight of the composition (Ba0.870Ca0.130)1.0111(Ti0.970Zr0.030)O3.
These weighed powders were dry-blended in a ball mill for 24 hours. Three parts by weight of a PVA binder was deposited on the surface of 100 parts by weight of the mixed powder with a spray drier.
The resulting granulated powder was charged in a mold and was pressed at 200 MPa with a pressing machine to form a discoidal compact. This compact may be further pressed with a cold isostatic pressing machine.
The compact was held in an electric furnace at a maximum temperature Tmax of 1200° C. for 5 hours and was sintered in the atmosphere for 24 hours in total.
The average equivalent circular diameter of the crystal grains, the percentage by number of crystal grains having an equivalent circular diameter of 25 μm or less (hereinafter referred to as D25), and the relative density of the resulting ceramic were measured. The average equivalent circular diameter was 1.33 μm, D25 was 100%, and the relative density was 96.0%. The crystal grain was observed mainly with a polarizing microscope. A small crystal grain size was determined with a scanning electron microscope (SEM). Photographic images taken with the polarizing microscope and the scanning electron microscope were processed to determine the average equivalent circular diameter and D25. The relative density was measurement in accordance with Archimedes' principle.
The ceramic was polished to a thickness of 0.5 mm, and its crystal structure was analyzed by X-ray diffraction. Only peaks corresponding to a perovskite structure were observed.
The composition of the ceramic was determined by X-ray fluorescence analysis. The analysis showed that Mn was 0.0121 mol per mole of a composition having the chemical formula of (Ba0.870Ca0.130)1.0111(Ti0.970Zr0.030)O3 and that Si and B were 0.0140 parts by weight and 0.0066 parts by weight, respectively, per 100 parts by weight of the composition. This indicates that the weighed composition agrees with the composition after sintering. The amounts of elements other than Ba, Ca, Ti, Zr, Mn, Si, B, and Cu were less than the detection limit or less than 0.0001 parts by weight. The valence of Mn in the sample was determined. A superconducting quantum interference device (SQUID) was used to measure magnetic susceptibility at a temperature in the range of 2 to 60 K. The valence was mostly 4+ as determined by the temperature dependence of magnetic susceptibility.
The crystal grains were again observed. The average equivalent circular diameter was not significantly changed by polishing.
Examples 2 to 38
Piezoelectric ceramics were manufactured in the same manner as in Example 1 except that the ratio of Ba, Ca, Ti, Zr, the first auxiliary component, and the second auxiliary component and the maximum sintering temperature Tmax were changed as shown in Table 1. The raw material of Cu was copper(II) oxide.












TABLE 1









First







auxiliary

Second auxiliary component


















Main component

component

Cu
Si
B
Total
Maximum




















Ba
Ca
Ti
Zr
A/B
Mn

Parts by
Parts by 
Parts by
Parts by
temperature



1-x
x
1-y
y
a
b
a-b
weight
weight
weight
weight
Tmax [° C.]






















Example 1
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 2
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 3
0.870
0.130
0.961
0.039
1.0111
0.0121
0.9990
None
0.0164
0.0066
0.0230
1200


Example 4
0.860
0.140
0.961
0.039
1.0111
0.0121
0.9990
None
0.0187
0.0066
0.0253
1200


Example 5
0.855
0.145
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 6
0.895
0.105
0.965
0.035
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 7
0.860
0.140
0.965
0.035
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 8
0.880
0.120
0.970
0.030
1.0112
0.0122
0.9990
None
0.0210
0.0066
0.0276
1200


Example 9
0.860
0.140
0.970
0.030
1.0111
0.0121
0.9990
None
0.0234
0.0066
0.0300
1200


Example 10
0.895
0.105
0.985
0.015
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 11
0.860
0.140
0.985
0.015
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 12
0.900
0.100
0.990
0.010
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 13
0.855
0.145
0.990
0.010
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 14
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1400


Example 15
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1350


Example 16
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1300


Example 17
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1250


Example 18
0.870
0.130
0.970
0.030
1.0046
0.0121
0.9925
None
0.0140
0.0066
0.0206
1200


Example 19
0.870
0.130
0.970
0.030
1.0146
0.0121
1.0025
None
0.0140
0.0066
0.0206
1200


Example 20
0.870
0.130
0.970
0.030
1.0038
0.0048
0.9990
None
0.0140
0.0066
0.0206
1200


Example 21
0.870
0.130
0.970
0.030
1.0390
0.0400
0.9990
None
0.0140
0.0066
0.0206
1200


Example 22
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
0.0010
None
None
0.0010
1200


Example 23
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
4.0000
None
None
4.0000
1200


Example 24
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0010
None
0.0010
1200


Example 25
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
4.0000
None
4.0000
1200


Example 26
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
None
0.0010
0.0010
1200


Example 27
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
None
4.0000
4.0000
1200


Example 28
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0005
0.0005
0.0010
1200


Example 29
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0100
0.0066
0.0166
1200


Example 30
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0250
0.0066
0.0316
1200


Example 31
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0300
0.0066
0.0366
1200


Example 32
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
2.0000
2.0000
4.0000
1200


Example 33
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
0.0005
0.0005
None
0.0010
1200


Example 34
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
2.0000
2.0000
None
4.0000
1200


Example 35
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
0.0005
None
0.0005
0.0010
1200


Example 36
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
2.0000
None
2.0000
4.0000
1200


Example 37
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
0.0034
0.0034
0.0034
0.0102
1200


Example 38
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
1.3000
1.3000
1.3000
3.9000
1200


Comparative 
0.905
0.095
0.955
0.045
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1400


Example 1














Comparative 
0.850
0.150
0.955
0.045
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 2














Comparative 
0.905
0.095
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 3














Comparative 
0.905
0.095
0.995
0.005
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 4














Comparative 
0.850
0.150
0.995
0.005
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 5














Comparative 
0.850
0.150
0.990
0.010
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
1200


Example 6














Comparative 
0.870
0.130
0.970
0.030
1.0041
0.0121
0.9920
None
0.0140
0.0066
0.0206
1200


Example 7














Comparative 
0.870
0.130
0.970
0.030
1.0151
0.0121
1.0030
None
0.0140
0.0066
0.0206
1200


Example 8














Comparative 
0.870
0.130
0.970
0.030
1.0035
0.0045
0.9990
None
0.0140
0.0066
0.0206
1200


Example 9














Comparative 
0.870
0.130
0.970
0.030
1.0440
0.0450
0.9990
None
0.0140
0.0066
0.0206
1200


Example 10














Comparative 
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0000
None
0
1200


Example 11














Comparative 
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
5.0000
None
5
1200


Example 12









The average equivalent circular diameter, D25, and the relative density were determined in the same manner as in Example 1. Table 2 shows the results.










TABLE 2






Average equivalent 

Relative



circular diameter

density 



[μm]
D25 [%]
[%]


















Example 1
1.33
100
96.0


Example 2
1.01
99.6
90.1


Example 3
1.06
99.7
91.3


Example 4
1.04
99.9
91.9


Example 5
1.02
99.9
91.2


Example 6
1.10
100
93.0


Example 7
1.13
99.9
95.0


Example 8
1.28
99.9
96.2


Example 9
1.36
99.9
96.3


Example 10
4.37
99.8
95.3


Example 11
4.60
100
95.7


Example 12
4.51
99.9
92.4


Example 13
4.59
99.8
91.5


Example 14
12.40
98.1
90.4


Example 15
9.97
99.5
90.6


Example 16
8.42
99.6
91.4


Example 17
4.69
99.7
91.0


Example 18
1.23
99.9
94.3


Example 19
4.53
99.8
95.6


Example 20
1.35
99.5
95.8


Example 21
2.22
99.8
96.7


Example 22
1.31
100
97.2


Example 23
2.66
99.9
96.1


Example 24
1.30
100
96.7


Example 25
3.22
99.9
96.6


Example 26
1.36
99.7
97.0


Example 27
3.12
99.8
96.2


Example 28
1.30
99.6
96.1


Example 29
1.33
99.8
96.4


Example 30
1.50
99.9
96.7


Example 31
2.64
99.8
96.6


Example 32
3.56
100
95.5


Example 33
1.30
99.8
96.7


Example 34
3.44
100
97.1


Example 35
1.36
99.9
96.0


Example 36
3.95
99.6
96.1


Example 37
1.33
100
96.1


Example 38
4.00
99.9
96.4


Comparative
0.92
100
88.8


Example 1





Comparative
0.81
100
81.2


Example 2





Comparative
1.03
100
90.2


Example 3





Comparative
5.61
99.9
90.0


Example 4





Comparative
5.57
99.2
91.2


Example 5





Comparative
5.02
99.8
90.6


Example 6





Comparative
18.4
40.0
90.4


Example 7





Comparative
0.86
100
85.0


Example 8





Comparative
2.03
98.9
92.3


Example 9





Comparative
3.40
98.2
90.2


Example 10





Comparative
0.61
100
85.6


Example 11





Comparative
17.5
42.0
90.4


Example 12












The composition analysis was performed in the same manner as in Example 1. Table 3 shows the results. The third auxiliary component in the table is an element other than Ba, Ca, Ti, Zr, Mn, Si, B, and Cu. Zero indicates less than the detection limit or less than 0.0001 parts by weight. Table 3 shows that the weighed composition in all the samples agreed with the composition after sintering. The valence of Mn in the sample was determined. A superconducting quantum interference device (SQUID) was used to measure magnetic susceptibility at a temperature in the range of 2 to 60 K. The valence was mostly 4+ in all the samples as determined by the temperature dependence of magnetic susceptibility.












TABLE 3









First







auxiliary

Second auxiliary component


















Main component

component

Cu
Si
B
Total
Third 




















Ba
Ca
Ti
Zr
A/B
Mn

Parts by
Parts by 
Parts by
Parts by
auxillary



1-x
x
1-y
y
a
b
a-b
weight
weight
weight
weight
component






















Example 1
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 2
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 3
0.870
0.130
0.961
0.039
1.0111
0.0121
0.9990
None
0.0164
0.0066
0.0230
0


Example 4
0.860
0.140
0.961
0.039
1.0111
0.0121
0.9990
None
0.0187
0.0066
0.0253
0


Example 5
0.855
0.145
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 6
0.895
0.105
0.965
0.035
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 7
0.860
0.140
0.965
0.035
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 8
0.880
0.120
0.970
0.030
1.0112
0.0122
0.9990
None
0.0210
0.0066
0.0276
0


Example 9
0.860
0.140
0.970
0.030
1.0111
0.0121
0.9990
None
0.0234
0.0066
0.0300
0


Example 10
0.895
0.105
0.985
0.015
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 11
0.860
0.140
0.985
0.015
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 12
0.900
0.100
0.990
0.010
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 13
0.855
0.145
0.990
0.010
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 14
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 15
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 16
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 17
0.900
0.100
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 18
0.870
0.130
0.970
0.030
1.0046
0.0121
0.9925
None
0.0140
0.0066
0.0206
0


Example 19
0.870
0.130
0.970
0.030
1.0146
0.0121
1.0025
None
0.0140
0.0066
0.0206
0


Example 20
0.870
0.130
0.970
0.030
1.0038
0.0048
0.9990
None
0.0140
0.0066
0.0206
0


Example 21
0.870
0.130
0.970
0.030
1.0390
0.0400
0.9990
None
0.0140
0.0066
0.0206
0


Example 22
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
0.0010
None
None
0.0010
0


Example 23
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
4.0000
None
None
4.0000
0


Example 24
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0010
None
0.0010
0


Example 25
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
4.0000
None
4.0000
0


Example 26
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
None
0.0010
0.0010
0


Example 27
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
None
4.0000
4.0000
0


Example 28
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0005
0.0005
0.0010
0


Example 29
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0100
0.0066
0.0166
0


Example 30
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0250
0.0066
0.0316
0


Example 31
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0300
0.0066
0.0366
0


Example 32
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
2.0000
2.0000
4.0000
0


Example 33
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
0.0005
0.0005
None
0.0010
0


Example 34
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
2.0000
2.0000
None
4.0000
0


Example 35
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
0.0005
None
0.0005
0.0100
0


Example 36
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
2.0000
None
2.0000
4.0000
0


Example 37
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
0.0034
0.0034
0.0034
0.0102
0


Example 38
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
1.3000
1.3000
1.3000
3.9000
0


Comparative 
0.905
0.095
0.955
0.045
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 1














Comparative 
0.850
0.150
0.955
0.045
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 2














Comparative 
0.905
0.095
0.961
0.039
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 3














Comparative 
0.905
0.095
0.995
0.005
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 4














Comparative 
0.850
0.150
0.995
0.005
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 5














Comparative 
0.850
0.150
0.990
0.010
1.0111
0.0121
0.9990
None
0.0140
0.0066
0.0206
0


Example 6














Comparative 
0.870
0.130
0.970
0.030
1.0041
0.0121
0.9920
None
0.0140
0.0066
0.0206
0


Example 7














Comparative 
0.870
0.130
0.970
0.030
1.0151
0.0121
1.0030
None
0.0140
0.0066
0.0206
0


Example 8














Comparative 
0.870
0.130
0.970
0.030
1.0035
0.0045
0.9990
None
0.0140
0.0066
0.0206
0


Example 9














Comparative 
0.870
0.130
0.970
0.030
1.0440
0.0450
0.9990
None
0.0140
0.0066
0.0206
0


Example 10














Comparative 
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
0.0000
None
0
0


Example 11














Comparative 
0.870
0.130
0.970
0.030
1.0111
0.0121
0.9990
None
5.0000
None
5
0


Example 12









Comparative Examples 1 to 12
Comparative ceramics were manufactured in the same manner as in Example 1 except that the ratio of Ba, Ca, Ti, Zr, the first auxiliary component, and the second auxiliary component were changed as shown in Table 1.
The average equivalent circular diameter and the relative density were determined in the same manner as in Example 1. Table 2 shows the results.
The composition analysis was performed in the same manner as in Example 1. Table 3 shows the results. The third auxiliary component in the table is an element other than Ba, Ca, Ti, Zr, Mn, Si, B, and Cu. Zero indicates less than the detection limit or less than 0.0001 parts by weight. Table 3 shows that the weighed composition in all the samples agreed with the composition after sintering.
A piezoelectric element according to an example of the present invention was then manufactured.
Manufacture of Piezoelectric Element and Characterization
Examples 1 to 38
Piezoelectric elements were manufactured using the piezoelectric ceramics according to Examples 1 to 38.
A gold electrode having a thickness of 400 nm was formed on the front and back sides of the discoidal ceramic by DC sputtering. A titanium film having a thickness of 30 nm was formed as an adhesion layer between the electrode and the ceramic. The ceramic having the electrodes was cut into a 10 mm×2.5 mm×0.5 mm plate-like piezoelectric element.
A 1.4 kV/mm electric field was applied to the piezoelectric element on a hot plate at a temperature in the range of 60° C. to 150° C. for 30 minutes to perform polarization treatment.
The Curie temperature, the piezoelectric constant d31, and the mechanical quality factor (Qm) of each of the piezoelectric elements manufactured using piezoelectric ceramics according to examples and comparative examples of the present invention were measured after polarization treatment. Table 4 shows the results. The “phase transition point” in the table indicates the presence of a phase transition point in the range of −20° C. to 100° C. “Yes” means the presence of a maximum dielectric constant in a very small alternating electric field at a frequency of 1 kHz at a measurement temperature from −20° C. to 100° C. “No” means the absence of the maximum dielectric constant. The Curie temperature was a temperature at which the dielectric constant reached its maximum in a very small alternating electric field at a frequency of 1 kHz. The piezoelectric constant d31 was measured by a resonance-antiresonance method. Table 4 shows its absolute value. The mechanical quality factor Qm was measured by the resonance-antiresonance method.
Resistivity was measured as a measure of the insulation property. Resistivity was measured using a non-polarizing piezoelectric element. Twenty seconds after a 10 V direct current bias was applied between two electrodes of a piezoelectric element, the resistivity of the piezoelectric element was measured from the leakage current. Table 4 shows the results.
When the resistivity is 1×109 Ω·cm or more, preferably 100×109 Ω·cm or more, the piezoelectric ceramic and the piezoelectric element have a satisfactory practical insulation property.













TABLE 4










Phase





|d31|

transition
Resistivity




[pm/V]
Qm
point
[109 Ω · cm]






















Example 1
68.0
712
No
124



Example 2 
74.1
665
No
103



Example 3 
76.1
662
No
112



Example 4 
75.8
675
No
102



Example 5 
75.3
653
No
110



Example 6 
72.0
686
No
111



Example 7 
71.5
667
No
111



Example 8 
69.8
708
No
112



Example 9 
67.4
708
No
117



Example 10
60.4
743
No
120



Example 11
59.3
732
No
131



Example 12
55.4
752
No
113



Example 13
57.6
746
No
105



Example 14
74.3
624
No
110



Example 15
74.3
624
No
120



Example 16
74.3
624
No
109



Example 17
74.3
624
No
106



Example 18
69.3
736
No
108



Example 19
72.3
720
No
105



Example 20
70.4
653
No
104



Example 21
68.5
986
No
120



Example 22
69.6
740
No
89



Example 23
714
731
No
88



Example 24
70.2
701
No
81



Example 25
70.0
700
No
93



Example 26 
69.2
725
No
94



Example 27 
70.3
717
No
87



Example 28 
72.4
698
No
87



Example 29 
71.3
713
No
91



Example 30 
70.5
722
No
109



Example 31 
71.0
707
No
92



Example 32 
68.4
699
No
88



Example 33 
69.9
720
No
89



Example 34 
68.3
715
No
96



Example 35 
70.8
709
No
90



Example 36 
71.2
707
No
91



Example 37 
72.3
692
No
96



Example 38 
70.3
710
No
98



Comparative
X
X
X
0.9



Example 1







Comparative
X
X
X
0.9



Example 2







Comparative 
74.1
700
Yes
0.9



Example 3







Comparative 
37.2
680
No
64



Example 4







Comparative
29.9
660
No
67



Example 5







Comparative
38.2
420
No
59



Example 6







Comparative
50.0
698
No
88



Example 7







Comparative 
X
X
X
0.9



Example 8







Comparative
63.0
210
No
30



Example 9







Comparative 
X
X
X
0.8



Example 10







Comparative 
X
X
X
0.8



Example 11







Comparative
38.2
483
No
98



Example 12














In all the examples, even when the electrodes were made of baked silver paste, the same characteristics as in the case of the gold electrode were obtained.
Comparative Examples 1 to 12
Piezoelectric elements were manufactured using the piezoelectric ceramics according to Comparative Examples 1 to 12 in the same manner as in Examples 1 to 38.
The piezoelectric elements were evaluated in the same manner as in Examples 1 to 38. Table 4 shows the results. The cross mark in the table indicates that resistivity was too low to measure.
Comparing Comparative Examples 1 and 2 with Examples 1 to 38, the value y of more than 0.039 results in a high sintering temperature and an insufficient relative density. This disadvantageously reduces resistivity and makes polarization difficult.
Comparing Comparative Example 3 with Examples 1 to 38, the value x of less than 0.100 results in a phase transition temperature in the range of −20° C. to 100° C. and low durability of the piezoelectric element.
Comparing Comparative Examples 4 and 5 with Examples 1 to 38, the value y of less than 0.010 disadvantageously results in |d31| of much less than 50 [pm/V].
Comparing Comparative Example 6 with Examples 1 to 38, the value x of more than 0.15 disadvantageously results in |d31| of much less than 50 [pm/V].
Comparing Comparative Example 7 with Examples 1 to 38, the value a of less than 0.9925+b results in the growth of abnormal grains and an average equivalent circular diameter of much more than 10 μm, disadvantageously resulting in a much reduced mechanical strength.
Comparing Comparative Example 8 with Examples 1 to 38, the value a of more than 1.0025+b results in suppressed grain growth and an insufficient relative density of 85.0. This disadvantageously reduces the resistivity and makes polarization treatment difficult.
Comparing Comparative Example 9 with Examples 1 to 38, the value b of less than 0.0048 results in Qm of much less than 600 and much reduced driving efficiency.
Comparing Comparative Example 10 and Examples 1 to 38, the value b of more than 0.0400 results in much reduced resistivity. This disadvantageously makes polarization impossible.
Comparing Comparative Example 11 with Examples 1 to 38, less than 0.001 parts by weight of the second auxiliary component results in suppressed grain growth and a reduced relative density. This disadvantageously reduces resistivity and makes polarization impossible.
Comparing Comparative Example 12 with Examples 1 to 38, more than 4.000 parts by weight of the second auxiliary component results in the growth of abnormal grains and an average equivalent circular diameter of much more than 10 μm, disadvantageously resulting in a much reduced mechanical strength.
Evaluation of Durability of Piezoelectric Element
In order to examine the durability of a piezoelectric element, Examples 1 to 13 and Comparative Example 3 were subjected to a cycle test in a thermostat. A hundred of temperature cycles of 25° C.→−20° C.→50° C.→25° C. were performed. Table 5 shows the rate of change in piezoelectric constant d31 in the cycle test.











TABLE 5







Piezoelectric
Piezoelectric




Phase
constant |d31|
constant |d31|
Rate of 



transition 
before cycle test 
after cycle test
change



point
[pC/N]
[pC/N]
[%]



















Example 1
No
68
65.8
−3.3


Example 2
No
74.1
70.7
−4.6


Example 3
No
76.1
73.7
−3.1


Example 4
No
75.8
73.1
−3.5


Example 5
No
75.3
73.6
−2.3


Example 6
No
72
69.1
−4.0


Example 7
No
71.5
68.3
−4.5


Example 8
No
69.8
67.4
−3.4


Example 9
No
67.4
64.8
−3.8


Example 10
No
60.4
58.7
−2.8


Example 11
No
59.3
57.2
−3.6


Example 12
No
55.4
53.8
−2.9


Example 13
No
57.6
55.2
−4.1


Comparative
Yes
74.1
58.2
−21.5


Example 3













Comparative Example 3 has a rate of change of much more than 10% and has lower durability than Examples 1 to 13. Thus, Comparative Example 3 is unfavorable.
A multilayered piezoelectric element according to an example of the present invention was manufactured.
Multilayered Piezoelectric Element
Example 39
A composition (Ba0.870Ca0.130)1.0111(Ti0.970Zr0.030)O3 was weighed as described below. This composition is represented by the general formula (Ba1-xCax)a(Ti1-yZry)O3, wherein x=0.130, y=0.030, and a=1.0111.
Barium carbonate, calcium carbonate, titanium oxide, and zirconium oxide were weighed as the raw materials of the main component such that Ba, Ca, Ti, and Zr satisfied the composition (Ba0.870Ca0.130)1.0111(Ti0.970Zr0.030)O3.
Manganese dioxide was weighed such that the b mol of the first auxiliary component Mn was 0.0121 mol per mole of the composition (Ba0.870Ca0.130)1.0111(Ti0.970Zr0.030)O3.
Silicon dioxide and boron trioxide were weighed such that the second auxiliary components Si and B were 0.0140 parts by weight and 0.0066 parts by weight on a metal basis, respectively, per 100 parts by weight of the composition (Ba0.870Ca0.130)1.0111(Ti0.970Zr0.030)O3.
The weighed powders were mixed with PVB and were formed into a green sheet having a thickness of 50 μm by a doctor blade method.
An electroconductive paste for an internal electrode was applied to the green sheet. The electroconductive paste was a 70% Ag-30% Pd alloy (Ag/Pd=2.33) paste. Nine green sheets to which the electroconductive paste had been applied were stacked and were fired at 1200° C. for 5 hours to yield a sintered body. The sintered body was cut into a 10 mm×2.5 mm piece. The side surface of the piece was polished. A pair of external electrodes (a first electrode and a second electrode) for alternately connecting internal electrodes were formed by Au sputtering. Thus, a multilayered piezoelectric element as illustrated in FIG. 2B was manufactured.
The observation of the internal electrodes of the multilayered piezoelectric element showed that the electrode material Ag—Pd and piezoelectric ceramic layers were alternately stacked on top of one another.
Before the evaluation of piezoelectricity, a sample was subjected to polarization treatment. More specifically, the sample was heated to a temperature in the range of 100° C. to 150° C. on a hot plate. While a voltage of 1.4 kV/mm was applied between the first electrode and the second electrode for 30 minutes, the sample was cooled to room temperature.
The evaluation of the piezoelectricity of the multilayered piezoelectric element showed that the multilayered piezoelectric element had satisfactory insulation property and had satisfactory piezoelectric property similar to the piezoelectric ceramic according to Example 1.
Example 40
A multilayered piezoelectric element was manufactured in the same manner as in Example 39 except that the raw materials of the main component were barium titanate having an average particle diameter of 100 nm (BT-01, manufactured by Sakai Chemical Industry Co., Ltd.), calcium titanate having an average particle diameter of 300 nm (CT-03, manufactured by Sakai Chemical Industry Co., Ltd.), and calcium zirconate having an average particle diameter of 300 nm (CZ-03, manufactured by Sakai Chemical Industry Co., Ltd.). The value a representing the ratio of the number of moles of Ba and Ca at the A site to the number of moles of Ti and Zr at the B site was controlled with barium oxalate and calcium oxalate.
The evaluation of the piezoelectricity of the multilayered piezoelectric element showed that the multilayered piezoelectric element had satisfactory insulation property and better piezoelectric property than Example 39. This is probably because the raw materials were perovskite metal oxides, which promoted grain growth, resulting in the dense multilayered piezoelectric element.
Comparative Example 13
A multilayered piezoelectric element was manufactured in the same manner as in Example 39 except that the composition was the same as in Comparative Example 2, the firing temperature was 1200° C., and the internal electrodes were made of a 95% Ag-5% Pd alloy (Ag/Pd=19).
The internal electrodes were observed with a scanning electron microscope. The observation showed that the internal electrodes were melted and interspersed as islands. Thus, the internal electrodes were not conductive, and the multilayered piezoelectric element was not polarized. Thus, the piezoelectric constant could not be measured.
Comparative Example 14
A multilayered piezoelectric element was manufactured in the same manner as in Comparative Example 13 except that the internal electrodes were made of a 5% Ag-95% Pd alloy (Ag/Pd=0.05).
The internal electrodes were observed with a scanning electron microscope. The observation showed that sintering of the electrode material Ag—Pd was insufficient. Thus, the internal electrodes were not conductive, and the multilayered piezoelectric element was not polarized. Thus, the piezoelectric constant could not be measured.
Comparative Example 15
A multilayered piezoelectric element was manufactured in the same manner as in Comparative Example 13 except that the internal electrodes were made of a 70% Ag-30% Pd alloy (Ag/Pd=2.33).
The internal electrodes were observed with a scanning electron microscope. Although the electrode material Ag—Pd and piezoelectric ceramic layers were alternately stacked on top of one another, resistivity between a pair of external electrodes of the multilayered piezoelectric element was as low as 108 Ω·cm or less because of insufficient sintering of the piezoelectric ceramic layers. Thus, the multilayered piezoelectric element was not polarized, and the piezoelectric constant could not be measured.
Example 41
A mixed powder was prepared in the same manner as in Example 39. The mixed powder was calcined at 1000° C. in the atmosphere for 3 hours while stirring to yield a calcined powder. The calcined powder was crushed in a ball mill. The calcined powder was mixed with PVB and was formed into a green sheet having a thickness of 50 μm by a doctor blade method. An electroconductive paste for an internal electrode was applied to the green sheet. The electroconductive paste was a Ni paste. Nine green sheets to which the electroconductive paste had been applied were stacked and were heat-pressed.
The heat-pressed multilayered body was fired in a tubular furnace. The heat-pressed multilayered body was fired to a temperature up to 300° C. in the atmosphere to remove the binder and was then held at 1200° C. for 5 hours in a reducing atmosphere (H2:N2=2:98, an oxygen concentration of 2×10−6 Pa). During cooling to room temperature, the oxygen concentration was 30 Pa at a temperature of 1000° C. or less.
The sintered body was cut into a 10 mm×2.5 mm piece. The side surface of the piece was polished. A pair of external electrodes (a first electrode and a second electrode) for alternately connecting internal electrodes were formed by Au sputtering. Thus, a multilayered piezoelectric element as illustrated in FIG. 2B was manufactured.
The observation of the internal electrodes of the multilayered piezoelectric element showed that the electrode material Ni and piezoelectric material layers were alternately stacked on top of one another. An electric field of 1.4 kV/mm was applied to the multilayered piezoelectric element in an oil bath at 100° C. for 30 minutes to perform polarization treatment. The evaluation of the piezoelectric property of the multilayered piezoelectric element showed that the multilayered piezoelectric element had satisfactory insulation property and had satisfactory piezoelectric property similar to the piezoelectric element according to Example 1.
Example 42
A liquid discharge head illustrated in FIGS. 3A and 3B was manufactured using the piezoelectric element according to Example 1. An ink was discharged in response to the input of an electric signal.
Example 43
A liquid discharge apparatus illustrated in FIG. 4 was manufactured using the liquid discharge head according to Example 42. An ink was discharged onto a recording medium in response to the input of an electric signal.
Example 44
An ultrasonic motor illustrated in FIG. 6A was manufactured using the piezoelectric element according to Example 1. Upon the application of an alternating voltage, the motor rotated.
Example 45
An optical apparatus illustrated in FIGS. 7A and 7B was manufactured using the ultrasonic motor according to Example 44. Upon the application of an alternating voltage, automatic focusing was observed.
Example 46
A dust removing device illustrated in FIGS. 9A and 9B was manufactured using the piezoelectric element according to Example 1. Upon the application of an alternating voltage after plastic beads were scattered, satisfactory dust removing efficiency was observed.
Example 47
An image pickup apparatus illustrated in FIG. 12 was manufactured using the dust removing device according to Example 44. Dust on a surface of an image pickup unit was satisfactorily removed, and images free of dust defects were obtained.
Example 48
A liquid discharge head illustrated in FIGS. 3A and 3B was manufactured using the multilayered piezoelectric element according to Example 40. An ink was discharged in response to the input of an electric signal.
Example 49
A liquid discharge apparatus illustrated in FIG. 4 was manufactured using the same liquid discharge head as in Example 48. An ink was discharged onto a recording medium in response to the input of an electric signal.
Example 50
An ultrasonic motor illustrated in FIG. 6B was manufactured using the multilayered piezoelectric element according to Example 40. Upon the application of an alternating voltage, the motor rotated.
Example 51
An optical apparatus illustrated in FIGS. 7A and 7B was manufactured using the ultrasonic motor according to Example 50. Upon the application of an alternating voltage, automatic focusing was observed.
Example 52
A dust removing device illustrated in FIGS. 9A and 9B was manufactured using the multilayered piezoelectric element according to Example 40. Upon the application of an alternating voltage after plastic beads were scattered, satisfactory dust removing efficiency was observed.
Example 53
An image pickup apparatus illustrated in FIG. 12 was manufactured using the same dust removing device as in Example 52. Dust on a surface of an image pickup unit was satisfactorily removed, and images free of dust defects were obtained.
Example 54
An electronic device illustrated in FIG. 14 was manufactured using the multilayered piezoelectric element according to Example 40. Upon the application of an alternating voltage, a loudspeaker operated.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2012-082686, filed Mar. 30, 2012, which is hereby incorporated by reference herein in its entirety.
INDUSTRIAL APPLICABILITY
A piezoelectric ceramic according to an embodiment of the present invention has a high and stable piezoelectric constant and a high and stable mechanical quality factor in a wide operating temperature range. The piezoelectric ceramic contains no lead and can reduce the load on the environment. Thus, the piezoelectric ceramic can be used for apparatuses manufactured using a large amount of piezoelectric ceramic, such as liquid discharge heads, ultrasonic motors, and dust removing devices, without problems.
REFERENCE SIGNS LIST


    
    
        1 first electrode
        2 piezoelectric ceramic
        3 second electrode
        101 piezoelectric element
        102 individual liquid chamber
        103 diaphragm
        104 liquid chamber partition wall
        105 discharge port
        106 communicating hole
        107 common liquid chamber
        108 buffer layer
        1011 first electrode
        1012 piezoelectric ceramic
        1013 second electrode
        201 oscillator
        202 rotor
        203 output shaft
        204 oscillator
        205 rotor
        206 spring
        2011 elastic ring
        2012 piezoelectric element
        2013 organic adhesive
        2041 metal elastic body
        2042 multilayered piezoelectric element
        310 dust removing device
        330 piezoelectric element
        320 diaphragm
        330 piezoelectric element
        331 piezoelectric ceramic
        332 first electrode
        333 second electrode
        336 first electrode surface
        337 second electrode surface
        310 dust removing device
        320 diaphragm
        330 piezoelectric element
        51 first electrode
        53 second electrode
        54 piezoelectric ceramic layer
        55 internal electrode
        501 first electrode
        503 second electrode
        504 piezoelectric ceramic layer
        505a internal electrode
        505b internal electrode
        506a external electrode
        506b external electrode
        601 main body of camera
        602 mount
        605 mirror box
        606 main mirror
        200 shutter unit
        300 main body chassis
        400 image pickup unit
        701 front lens group
        702 rear lens group (focus lens)
        711 removable mount
        712 fixed barrel
        713 linear guide barrel
        714 front lens group barrel
        715 cam ring
        716 rear lens group barrel
        717 cam roller
        718 screw
        719 roller
        720 rotation transmitting ring
        722 driven roller
        724 manual focus ring
        725 ultrasonic motor
        726 wave washer
        727 ball race
        728 focus key
        729 joint
        732 washer
        733 low-friction sheet
        881 liquid discharge apparatus
        882 exterior
        883 exterior
        884 exterior
        885 exterior
        887 exterior
        890 recovering section
        891 recording portion
        892 carriage
        896 main body of apparatus
        897 automatic feeder
        898 outlet
        899 conveying unit
        901 optical device
        908 release button
        909 electronic flash unit
        912 loudspeaker
        914 microphone
        916 fill light unit
        931 main body
        932 zoom lever
        933 power switch

## Claims

1. A piezoelectric ceramic, comprising: a main component containing a perovskite metal oxide having the following general formula (1); Mn as a first auxiliary component; and a second auxiliary component containing at least one element selected from the group consisting of Cu, B, and Si,


(Ba1-xCax)a(Ti1-yZry)O3(0.100≦x≦0.145,0.010≦y≦0.039)  (1)

wherein the amount b (mol) of Mn per mole of the metal oxide is in the range of 0.0048≦b≦0.0400, the second auxiliary component content on a metal basis is 0.001 parts by weight or more and 4.000 parts by weight or less per 100 parts by weight of the metal oxide, and the value a of the general formula (1) is in the range of 0.9925+b≦a≦1.0025+b.

2. The piezoelectric ceramic according to claim 1, wherein the average equivalent circular diameter of a plurality of crystal grains of the piezoelectric ceramic is 1 μm or more and 10 μm or less, and crystal grains having an equivalent circular diameter of 25 μm or less constitute 99 percent by number or more of the total crystal grains.

3. The piezoelectric ceramic according to claim 1, wherein the piezoelectric ceramic has a relative density of 90% or more and 100% or less.

4. A method for manufacturing the piezoelectric ceramic according to claim 1, comprising: sintering a compact containing Ba, Ca, Ti, Zr, Mn, and at least one metallic element selected from the group consisting of Cu, B, and Si at a temperature of 1200° C. or less.

5. A piezoelectric element, comprising: a piezoelectric ceramic; a first electrode; and a second electrode, wherein the piezoelectric ceramic is the piezoelectric ceramic according to claim 1.

6. A multilayered piezoelectric element, comprising: piezoelectric ceramic layers and electrode layers alternately stacked on top of one another, the electrode layers including an internal electrode, wherein the piezoelectric ceramic layers are formed of the piezoelectric ceramic according to claim 1.

7. The multilayered piezoelectric element according to claim 6, wherein the internal electrode contains Ag and Pd, and the weight ratio M1/M2 of the weight M1 of Ag to the weight M2 of Pd is in the range of 0.25≦M1/M2≦4.0.

8. The multilayered piezoelectric element according to claim 6, wherein the internal electrode contains at least one of Ni and Cu.

9. A method for manufacturing the multilayered piezoelectric element according to claim 6, comprising: (A) preparing a slurry of a metallic compound powder containing at least Ba, Ca, Ti, Zr, Mn, and at least one element selected from the group consisting of Cu, B, and Si; (B) forming a compact from the slurry; (C) forming an electrode on the compact; and (D) sintering a plurality of the compacts at a temperature of 1200° C. or less to manufacture the multilayered piezoelectric element.

10. The method for manufacturing the multilayered piezoelectric element according to claim 9, wherein the slurry contains a perovskite metal oxide containing at least one of Ba and Ca and at least one of Ti and Zr.

11. A liquid discharge head, comprising: a liquid chamber; and a discharge port in communication with the liquid chamber, wherein the liquid chamber has a vibrating unit that includes the piezoelectric element according to claim 5.

12. A liquid discharge apparatus, comprising: a recording medium conveying unit; and the liquid discharge head according to claim 11.

13. An ultrasonic motor, comprising: a vibrating member that includes the piezoelectric element according to claim 5 and a moving body in contact with the vibrating member.

14. An optical apparatus, comprising the ultrasonic motor according to claim 13 in a drive unit.

15. A vibratory apparatus, comprising a vibrating member that includes the piezoelectric element according to claim 5.

16. A dust removing device, comprising the vibratory apparatus according to claim 15.

17. An image pickup apparatus, comprising: the dust removing device according to claim 16 and an image pickup element unit, wherein the dust removing device includes a vibrating member on the light incident side of the image pickup element unit.

18. An electronic device, comprising a piezoelectric acoustic component that includes the piezoelectric element according to claim 5.

19. A liquid discharge head, comprising: a liquid chamber; and a discharge port in communication with the liquid chamber, wherein the liquid chamber has a vibrating unit that includes the multilayered piezoelectric element according to claim 6.

20. A liquid discharge apparatus, comprising: a recording medium conveying unit; and the liquid discharge head according to claim 19.

21. An ultrasonic motor, comprising: a vibrating member that includes the multilayered piezoelectric element according to claim 6; and a moving body in contact with the vibrating member.

22. An optical apparatus, comprising the ultrasonic motor according to claim 21 in a drive unit.

23. A vibratory apparatus, comprising a vibrating member that includes the multilayered piezoelectric element according to claim 6.

24. A dust removing device, comprising the vibratory apparatus according to claim 23.

25. An image pickup apparatus, comprising: the dust removing device according to claim 24 and an image pickup element unit, wherein the dust removing device includes a vibrating member on the light incident side of the image pickup element unit.

26. An electronic device, comprising a piezoelectric acoustic component that includes the multilayered piezoelectric element according to claim 6.

27. A piezoelectric material comprising:
a perovskite metal oxide containing Ba, Ca, Ti, Zr, Mn, and at least one element selected from the group consisting of Cu, B, and Si,
wherein the ratio x of the amount of Ca (mol) to the sum of the amounts of Ba and Ca (mol) is in the range of 0.100≦x≦0.145, and
the ratio y of the amount of Zr (mol) to the sum of the amounts of Ti and Zr (mol) is in the range of 0.010≦y≦0.039, and
wherein the amount b (mol) of Mn per 100 parts by weight of the perovskite metal oxide is in the range of 0.0048≦b≦0.0400,
the amount (parts by weight) of the at least one element selected from the group consisting of Cu, B, and Si is 0.001 parts by weight or more and 4.000 parts by weight or less, and
the ratio a of the sum of the amounts of Ba and Ca (mol) to the sum of the amounts of Ti and Zr (mol) is in the range of 0.9925+b≦a≦1.0025+b.

28. A piezoelectric element comprising:
a first electrode;
a piezoelectric material portion; and
a second electrode,
wherein the piezoelectric material portion comprises the piezoelectric material according to claim 27.

29. A multilayered piezoelectric element comprising:
piezoelectric material layers; and
electrode layers including an internal electrode,
wherein the piezoelectric material layers and the electrode layers are alternately stacked, and
the piezoelectric material layers comprise the piezoelectric material according to claim 27.

30. An electronic apparatus comprising the piezoelectric element according to claim 28.

31. An electronic apparatus comprising the multilayered piezoelectric element according to claim 29.