Patent ID: 12230444

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Equations such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

Hereinafter, embodiments of a dielectric material according to the present disclosure, a device including the same, and a method of preparing the dielectric material will be described in greater detail with reference to the appended drawings. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

In the drawings, the size or thickness of each element may be exaggerated for clarity of description. When the terms “about” or “substantially” are used in this specification in connection with a numerical value, it is intended that the associated numerical value includes a manufacturing tolerance (e.g., ±10%) around the stated numerical value. Further, regardless of whether numerical values are modified as “about” or “substantially,” it will be understood that these values should be construed as including a manufacturing or operational tolerance (e.g., ±10%) around the stated numerical values.

Hereinafter, it will also be understood that when an element is referred to as being “on” or “above” another element, it can be “directly on and in contact” with the other element, or “in non-contact” with intervening elements thereon. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. When a portion is referred to as “comprising” or “including” an element, it means that, unless stated specifically otherwise, another element can further be included; rather than excluded. As used herein, the term “combination” includes a mixture, an alloy, a reaction product, and the like unless otherwise stated.

Although the terms “first,” “second,” “third,” “fourth,” “fifth,” “sixth,” etc., may be used herein to describe various elements and/or components, these elements and/or components should not be limited by these terms. These terms are used only to distinguish one component from another, not for purposes of limitation. The term “or” refers to “and/or” unless otherwise stated. As used herein, the term “connected” may refer to being connected directly or indirectly, or via a communication network.

As used herein, the terms “an embodiment”, “embodiments”, and the like indicate that elements described with regard to an embodiment are included in at least one embodiment described in this specification and may or may not present in other embodiments. In addition, it may be understood that the described elements are combined in any suitable manner in various embodiments. Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one or ordinary skill in the art to which this application belongs. All patents, patent applications, and other cited references are incorporated herein by reference in their entirety. However, in the event of any conflict or inconsistency between terms used herein and terms of the cited references, the terms used in this specification take precedence over the terms of the cited references. While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modification, variations, improvements, and substantial equivalents.

A dielectric material according to one or more embodiments may include a NaNbO3ternary material having a permittivity of 600 or more at 1 kHz, a temperature coefficient of capacitance (TCC), expressed by Equation 1, of about −15% to about 15% in a range of about −55° C. to about +200° C., wherein the NaNbO3ternary material includes a perovskite phase with a Sm element substituted into a Na site:
TCC (%)=[(C−CRT)/CRT]×100  [Equation 1]

wherein, in Equation 1, C is a capacitance value measured within a temperature range of −55° C. to 200° C., and CRTis a capacitance value measured at 25° C.

BaTiO3, which is known as a ceramic capacitor material, has a Curie temperature (Tc) as low as 120° C. However, the maximum operating temperature required for a commercial X9R multi-layered ceramic capacitor (MLCC) is 200° C. Considering that an ultrathin-film MLCC is a core of the high-temperature electronic circuit assembly, an electronic material which is stable in a wide temperature range is beneficial.

NaNbO3has a Curie temperature (Tc) as high as about 350° C. NaNbO3has a low permittivity of 200 at room temperature. To increase permittivity at room temperature, a NaNbO3binary material including a ABO3perovskite phase in which a different element is substituted into the sodium (Na) site of NaNbO3is used in general. For example, a NaNbO3binary material having a perovskite phase in which a rare earth element is substituted into the Na site of NaNbO3may be used. However, in general, with an increase in permittivity of the NaNbO3binary material, temperature stability in the range of −55° C. to +200° C. also changes.

For example, the dielectric material according to one or more embodiments may include a NaNbO3ternary material including a perovskite phase in which a samarium (Sm) element is substituted into a Na site. The NaNbO3ternary material may have a permittivity of 600 or more at 1 kHz, a temperature coefficient of capacitance (TCC), expressed by Equation 1, of −15% to 15% in the range of −55° C. to +200° C.

A specific resistivity of the NaNbO3ternary material may be greater than 1×1012Ωcm and/or a dielectric loss factor (tan δ) of the NaNbO3ternary material may be 2.0 or less.

The dielectric material according to one or more embodiments may be a ceramic ferroelectric material that exhibits high permittivity even in a high electric field to which a high DC voltage is applied. Such a ferroelectric material includes a portion having a low AC sweeping energy barrier. Due to this, the ferroelectric material may exhibit high permittivity in response to AC sweeping even under a high electric field. For example, dielectric characteristics can be maintained even under a high electric field. In addition, stability may be maintained at a temperature, including high temperatures, in the range of −55° C. to +200° C.

The NaNbO3ternary material according to one or more embodiments may include a compound represented by Formula 1:
(1−x−y)NaNbO3−xSm1/3NbO3−y(M1)a(M2)bO3[Formula 1]

wherein, in Formula 1, M1 may be at least one of a Group 1 element, a Group 2 element, or a Group 15 element of the Periodic Table of the Elements, or a combination thereof; M2 may be at least one of a Group 4 transition metal element or a Group 5 transition metal element of the Periodic Table of the Elements, or a combination thereof; and 0.1<x≤0.15, 0.001≤y≤0.1, 0<a<1, 0<b<1, and a+b=1.

The NaNbO3and Sm1/3NbO3in in the compound may form a solid solution. The solid solution may include a plurality of domains, and a polar nano region in the plurality of domains. The dielectric material includes a polar region (e.g., a polar nano region, polar layer, and/or a polar portion) in the plurality of domains, and thus forms a relaxor-ferroelectric material.

FIG.7is a conceptual diagram for explaining a case where spontaneous polarization in a thin film ferroelectric of the related art is fixed and thus permittivity is reduced; andFIG.8is a conceptual diagram to describe a case in which, when a dielectric material according to some example embodiments is a relaxer-ferroelectric, high permittivity may be retained even under a high electric field due to a polar nano region (PNR) included in the relaxer-ferroelectric.

InFIG.7, a ferroelectric100may be a NaNbO3binary dielectric of which the thickness is thinned to be hundreds of nanometers according to a high-integration and miniaturization trend. Each domain120of the ferroelectric100has a polarization130. The ferroelectric100may include boundaries110between domains120. When an electric field is not applied to the ferroelectric100, the polarizations130of each domain120is directed to an arbitrary direction as shown in (a). As a high DC voltage (e.g., a DC bias140) is applied to the ferroelectric100, the ferroelectric is put under a high electric field. Accordingly, the polarization130of each domain120of the ferroelectric100is generally aligned in the same direction as the DC bias140, and the ferroelectric100as a whole exhibits a polarization in the same direction as the DC bias140. Thereafter, as shown in (c), even when the direction of the alternating current (AC) bias150is changed to the opposite direction of the DC bias while the DC bias140is still being applied to the ferroelectric100, the direction of the polarization130of each domain120is not changed and maintains the same direction as the DC bias140. Therefore, as described above, after the polarization130of the ferroelectric100is fixed in the direction of the DC bias140, the polarization130does not react to the change of the AC bias150, and permittivity of the ferroelectric100is rapidly decreased. As a result, the ferroelectric100cannot effectively function as a dielectric material according the high-integration and miniaturization trend.

However, the ferroelectric according to some example embodiments may be a ceramic ferroelectric that exhibits higher permittivity than NaNbO3binary dielectric, even under a high electric field wherein a high DC voltage is applied. The ceramic ferroelectric includes a portion with a low energy barrier to an AC sweep, and the ferroelectric reacts to an AC sweep even under a high electric field due to the portion with a low energy barrier to an AC sweep and exhibits higher permittivity than NaNbO3binary dielectric. For example, the dielectric properties can be maintained even under a high electric field.

The dielectric material including the compound according to some example embodiments may be referred to as a relaxer-ferroelectric.

Referring toFIG.8the relaxer-ferroelectric may retain high permittivity even under a high electric field (for example, under a high DC bias) because it reacts well to AC bias due to a polar nano region (PNR) included in the relaxer-ferroelectric.

InFIG.2, the relaxer-ferroelectric includes a ferroelectric205showing the first polarization characteristic, and the polar region210showing the second polarization characteristics in the ferroelectric205.

The ferroelectric205is a dielectric material and/or a dielectric layer including the compound represented by Formula 1. The polar region210may be a region where a main element is substituted with another element in a part of the ferroelectric205. For example, when the ferroelectric205is NaNbO3ternary material, the polar region210may be formed by a defect cluster where a sodium (Na) cation in an A site of NaNbO3is substituted with samarium (Sm) ion. The polar region210may be a polar nano region (PNR). The first polarization characteristic and the second polarization characteristic may be different from each other. The first polarization characteristic and the second polarization characteristic may include a spontaneous polarization characteristic. The relaxer-ferroelectric200may be expressed as a relaxer-ferroelectric layer. The polar region210may be expressed as a polar layer or polar portion.

In the relaxer-ferroelectric200ofFIG.8, the ferroelectric205includes a plurality of domains, like the ferroelectric100ofFIG.7, but, for convenience and clarity of illustration, the domains are not shown inFIG.8. Each domain included in the ferroelectric205may include a plurality of polar regions210. The polarization characteristics of the region except for the polar region210in each domain may differ from that of the polar region210.

For example, the dielectric material including the compound, according to some example embodiments, becomes a relaxer-ferroelectric by forming PNRs. Since the polarization miniaturized to a nano size has a low energy barrier to an AC sweep even under a high electric field and DC bias, the fixation of the polarization is relieved. As a result, the dielectric material shows a relatively high effective permittivity for an AC bias change.

Without being limited to a particular theory or result, the dielectric material that formed the PNR and became a relaxer-ferroelectric increases the structural diversity due to the difference in ion radius of the substituent Sm as described above, and the Curie temperature (Tc) can be finely modified to allow permittivity to be insensitive to temperature change. As a result, permittivity of the dielectric material according to temperature becomes stable.

Hereinafter, the working principle of the dielectric material according to one or more embodiments will be described in brief.

The relaxor-ferroelectric material, which is a dielectric material according to an embodiment, may include: a ferroelectric material, which exhibits a first polarization characteristic; and a polar region, which is included in the ferroelectric material and exhibits a second polarization characteristic. The first polarization characteristic and the second polarization characteristic may be different from each other. The first polarization characteristic and the second polarization characteristic may include spontaneous polarization characteristics. Herein, the relaxor-ferroelectric material may be expressed as a relaxor-ferroelectric layer. The polar region may be expressed as a polar layer or a polar portion. The polar region is a region including a solid solution that includes a different material from the ferroelectric material. The ferroelectric material may be expressed as a ferroelectric layer. The ferroelectric material may have a thickness of about 1000 nm or less. When the ferroelectric material is a NaNbO3ternary material, the relaxor-ferroelectric material including the polar region may have an orthorhombic crystal structure.

For example, the polar region may be expressed as a region in which main elements of the ferroelectric material are substituted with other elements. When the ferroelectric material is NaNbO3(NN), the polar region, which is a region formed by a defect cluster in which Na at A-site of NN is substituted with a first element and/or a second element that is different from Na, may be a polar nano region (PNR). The first element may be an element that serves as a donor, and the second element may be an element that serves as an acceptor. The first element and the second element may have different atomic radii.

The first element may be, for example, a Sm element. The second element may be, for example, a Group 1 element, a Group 2 element, a Group 15 metal element of the Periodic Table of the Elements, or a combination thereof. For example, the second element may be Na, Ba, Sr, Ca, Na, Bi, or a combination thereof.

The first polarization characteristic of the ferroelectric material may be different from the second polarization characteristic of the polar region due to the difference in the material of the polar region and the ferroelectric material, as described above. Accordingly, an energy barrier of the ferroelectric material and an energy barrier of the polar region, which respond to AC sweeping, may be different from each other. In one or more embodiments, the energy barrier of the polar region, which responds to AC sweeping, may be lower than the energy barrier of the ferroelectric material. For this reason, in the case where the relaxor-ferroelectric material is under a high DC bias, the total polarization of the ferroelectric material is fixed in the DC bias direction due to a high electric field by the DC bias, and there is no response to an AC bias applied to the relaxor-ferroelectric material, while the polar region may directly respond to an AC bias, and thus the polarization direction of the polar region may change in response to an AC bias. As a result, the relaxor-ferroelectric material may exhibit a high permittivity even under a high electric field caused by a high DC voltage.

The dielectric material according to one or more embodiments may include a NaNbO3ternary material including a perovskite phase in which a Sm element is substituted into a Na site of NaNbO3. The NaNbO3ternary material may shift the Curie temperature (Tc) at which permittivity sharply increases, to room temperature, thus improving the overall permittivity. At the same time, while the NaNbO3ternary material becomes a relaxor, a change in permittivity (and/or capacity) in a range of −55° C. to +200° C. may be significantly reduced, and temperature stability may be improved.

The NaNbO3ternary material according to one or more embodiments may include a compound represented by Formula 2.
(1−x−y)NaNbO3−xSm1/3NbO3−y(M1)c(M1′)dTiO3[Formula 2]wherein, in Formula 2,M1 and M1′ may each independently be at least one of a Group 1 element, a Group 2 element, or a Group 15 element of the Periodic Table of the Elements, and/or a combination thereof; and 0.1≤x≤0.15, 0.001≤y≤0.03, 0<c<1, 0<d<1, and c+d=1.

For example, in Formula 2, M1 and M1′ may each independently be Ba, Sr, Ca, Na, Bi, or a combination thereof.

For example, in Formula 2, y may be 0.001 to 0.02.

The NaNbO3ternary material according to one or more embodiments may include a compound represented by Formula 3.
(1−x−y)NaNbO3−xSm1/3NbO3−y(M1)TaO3[Formula 3]

wherein, in Formula 3, M1 may be a Group 1 element of the Periodic Table of the Elements; and 0.1<x≤0.15, and 0.001≤y≤0.1.

For example, in Formula 3, M1 may be Na.

For example, in Formula 3, y may be 0.01 to 0.1.

The NaNbO3ternary material according to one or more embodiments may include (1−x−y)NaNbO3−xSm1/3NbO3−yBaTiO3, (1−x−y)NaNbO3−xSm1/3NbO3−ySrTiO3, (1−x−y)NaNbO3−xSm1/3NbO3−yCaTiO3, (1−x−y)NaNbO3−xSm1/3NbO3−yBicNadTiO3, and/or (1−x−y)NaNbO3−xSm1/3NbO3−y′NaTaO3, wherein x may be from 0.1 to 0.15, y may be from 0.001 to 0.03, y′ may be from 0.001 to 0.1, c and d may each independently be larger than 0 to less than 1, and the sum of c and d may be 1.

The NaNbO3ternary material according to one or more embodiments may include (0.85−y)NaNbO3−0.15Sm1/3NbO3−yBaTiO3, (0.85−y)NaNbO3−0.15Sm1/3NbO3−ySrTiO3, (0.85−y)NaNbO3−0.15Sm1/3NbO3−yCaTiO3, (0.85−y)NaNbO3−0.15Sm1/3NbO3−yBicNadTiO3, and/or (0.85−y)NaNbO3−0.15Sm1/3NbO3−y′NaTaO3, wherein y may be from 0.001 to 0.03, y′ may be from 0.001 to 0.1, c and d may each independently be larger than 0 or less than 1, and the sum of c and d may be 1.

A device according to one or more embodiments may include: a first electrode; a second electrode facing the first electrode; and a dielectric layer arranged between the first electrode and the second electrode, wherein the dielectric layer includes the dielectric material described above.

The device may be used in an electric circuit, an electronic circuit, an electromagnetic circuit, and/or the like, and is not particularly limited as long as the device provides an electrical output for an electrical input. The device may be (and/or include) a passive and/or an active element. The electrical input may be current or voltage, and the current may be direct current or alternating current. The electrical input may be a continuous input or an intermittent input with a constant cycle. The device may store electrical energy, electrical signals, magnetic energy, and/or magnetic signals. The device may be a semiconductor, a memory, a processor, and/or the like. The device may be, for example, a resistor, an inductor, a capacitor, and/or the like.

The device may be, for example, a capacitor.

For example, the device may be a multi-layered ceramic capacitor. The device may include: a plurality of first electrodes; a plurality of second electrodes, the plurality of first electrodes and the plurality of second electrodes being alternately arranged; and a plurality of dielectric layers arranged respectively between the plurality of first electrodes and the plurality of second electrodes.

FIG.5is a schematic view of a multi-layered ceramic capacitor (MLCC) according to at least one example embodiment.FIG.6is a schematic view showing protective layers respectively arranged on the upper portion and the lower portion of the dielectric layer ofFIG.5.

Referring toFIG.5, a multi-layered ceramic capacitor (MLCC)1may include: a plurality of internal electrodes12; and a dielectric layer11alternately disposed between the plurality of internal electrodes12. The internal electrode12may be a first electrode and/or a second electrode. For example, the first electrodes may correspond to a plurality of internal electrodes12connected to one of an external electrode13, and the second electrodes may correspond to a plurality of internal electrodes12connected to another external electrode13. The dielectric layer11may include the dielectric material according to one or more embodiments. The device may further include a protective layer on at least a portion of the upper portion and the lower portion of the dielectric layer.

Referring toFIG.6, the dielectric layer11may include four dielectric layers, and the protective layers10may be arranged on the upper portion and the lower portion of the dielectric layers, respectively. The protective layer may be a single layer or a multilayer of at least two layers. The protective layer10may prevent an alkali metal, such as Na, from easily volatilizing when the dielectric material is heat-treated in an oxidizing atmosphere. The protective layer10may include, for example, BaTiO3, SrTiO3, BaZrO3, BaTiO3, PbTiO3, PbZrO3, SrZrO3, CaTiO3, CaZrO3, BaSnO3, BaFeO3, and/or a combination thereof. However, the example embodiments are not limited thereto, and the protective layer10may include other metal oxides art, except for those of monovalent metal elements.

Referring toFIG.5, the adjacent internal electrodes12may be electrically separated from one another by the dielectric layer11disposed therebetween. In the multi-layered ceramic capacitor1, as the internal electrodes12and the dielectric layer11are alternately stacked, the dielectric layer11disposed between the adjacent internal electrodes12may act as a single unit capacitor. In the multi-layered ceramic capacitor1, the number of internal electrodes12and the number of dielectric layers11, which are alternately stacked, may each independently be, for example, 2 or larger, 5 or larger, 10 or larger, 20 or larger, 50 or larger, 100 or larger, 200 or larger, 500 or larger, 1,000 or larger, 2,000 or larger, 5,000 or larger, and/or 10,000 or larger. The multi-layered ceramic capacitor1may provide capacitance through the stacked structure in which a plurality of unit capacitors are stacked. As the number of stacked internal electrodes12and dielectric layers11increases, a contact area thereof may increase, thus increasing the capacitance. The area of the internal electrodes12may be smaller than the area of the dielectric layer11. The plurality of the internal electrodes12may each have the same area. However, the adjacent internal electrodes12may be disposed not to be in the same position along the thickness direction of the multi-layered ceramic capacitor1, and to partially protrude alternately in the directions of the opposing side surfaces of the multi-layered ceramic capacitor1. The internal electrodes12may be formed, for example, using a conductive paste including at least one selected from nickel (Ni), copper (Cu), palladium (Pd), a palladium-silver (Pd—Ag) alloy, and/or the like. A printing method of the conductive paste may be a screen printing method and/or a gravure printing method, but is not necessarily limited thereto. The internal electrodes12may have a thickness of, for example, about 100 nm to about 5 μm, about 100 nm to about 2.5 μm, about 100 nm to about 1 μm, about 100 nm to about 800 nm, about 100 nm to about 400 nm, or about 100 nm to about 200 nm.

Referring toFIG.5, a plurality of the internal electrodes12, which are alternately stacked to partially protrude in directions of opposing side surfaces of the laminated ceramic capacitor1, may be electrically connected to external electrodes13. The external electrodes13may be disposed, for example, on a laminate including the plurality of internal electrodes12and the dielectric layer11alternately disposed between the plurality of the internal electrodes12and connected to the internal electrodes12. The multi-layered ceramic capacitor1may include the internal electrodes12, and external electrodes13respectively connected to the internal electrodes12. The multi-layered ceramic capacitor1may include, for example, a pair of external electrodes13surrounding the opposite sides of a laminate structure including the internal electrodes12and the dielectric layer11. The external electrodes13may be any material having electrical conductivity, such as metal, or may be a specific material, which may be determined considering electrical characteristics, structural stability, and the like. The external electrodes13may have, for example, a multilayer structure. The external electrodes13may, for example, include: an electrode layer, which contacts the laminate and the internal electrodes12and includes Ni; and a plating layer on the electrode layer.

For example, the dielectric layer11of the multi-layered ceramic capacitor1may be disposed to have an area that is larger than the area of the adjacent internal electrodes12. The dielectric layer11disposed between the adjacent internal electrodes12in the multi-layered ceramic capacitor1may be, for example, connected to each other. The dielectric layer11disposed between the adjacent internal electrodes12may be connected to one another on the sides in contact with the external electrodes13in the multi-layered ceramic capacitor1. For example, the external electrodes13may be omitted. In the case of the external electrodes13being omitted, the internal electrodes12protruding to the sides of the multi-layered ceramic capacitor1may be connected to a power source.

In a unit capacitor including the adjacent internal electrodes12and the dielectric layers11disposed therebetween, a thickness of the dielectric layer11and/or a gap between the adjacent internal electrodes12may be, for example, about 10 nm to about 1 μm, about 100 nm to about 800 nm, about 100 nm to about 600 nm, or about 100 nm to about 300 nm. In the unit capacitor including the adjacent internal electrodes12and the dielectric layers11disposed therebetween, the dielectric layer11may have a permittivity of 600 or larger at 1 kHz at room temperature (25° C.), and a temperature coefficient of capacitance (TCC), expressed by Equation 1, of about −15% to about 15% in a range of about −55° C. to about +200° C.

By the inclusion of the dielectric layer11having such a small thickness and high permittivity, the multilayer stack capacitor1may have increased capacitance and have reduced thickness and volume. Accordingly, a smaller, thinner capacitor with higher capacity may be provided.

FIG.9Aillustrates a circuit configuration of a memory cell of a memory device including a semiconductor device and a capacitor.FIG.9Bis a schematic diagram showing a semiconductor apparatus according to some example embodiments.

Referring toFIGS.9A and9B, the semiconductor apparatus D70may be included in a memory device as a memory cell and may include a transistor D61and a capacitor D60electrically connected to, for example, a source region730of the transistor D61. The memory device may include a plurality of bit lines and a plurality of word lines and may further include a plurality of the memory cells. Each word line may be electrically connected to a gate electrode710of the transistor D61, and each bit line may be electrically connected to a drain region720of the transistor D61. An electrode of the capacitor D60may be connected to, for example, a voltage controller (not shown).

The semiconductor apparatus D70may be included in a plurality of semiconductor apparatuses, for example in a memory cell array.

The capacitor D60may be, for example the multi-layer capacitor1ofFIG.5and/or a capacitor including, in the dielectric, the compound represented by Formula 1. One of the outer electrodes13of the capacitor D60and one of the source region730and the drain region720of the transistor D61may be electrically connected by a contact62. The contact62may include a conductive material, such as tungsten, copper, aluminum, polysilicon, and/or the like.

The field effect transistor D61may include a substrate780including a source region730, a drain region720, and a channel760, and a gate electrode710facing the channel760. A dielectric layer750may be between the substrate780and the gate electrode710.

The semiconductor apparatus D70, the capacitor D60, and/or the field effect transistor D61may be included, in an electronic device architecture.

FIGS.10and11are conceptual views schematically illustrating electronic device architectures applicable to electronic devices according to some example embodiments.

Referring toFIG.10, an electronic device architecture3000may include a memory unit3010, an arithmetic logic unit (ALU)3020, and a control unit3030. The memory unit3010, the ALU3020, and the control unit3030may be electrically connected to each other. For example, the electronic device architecture3000may be implemented as a single chip including the memory unit3010, the ALU3020, and/or the control unit3030. For example, the memory unit3010, the ALU3020, and the control unit3030may be connected to each other through metal lines on a chip for direct communication therebetween. The memory unit3010, the ALU3020, and/or the control unit3030may be monolithically integrated on a single substrate to form a single chip. Input/output devices2000may be connected to the electronic device architecture (chip)3000. The control unit3030may include processing circuitry such as hardware including logic circuits; a hardware/software combination such as a processor executing software; and/or a combination thereof. For example, the processing circuitry more specifically may include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), and programmable logic unit, a microprocessor, application-specific integrated circuit (ASIC), etc. Similarly, though the electronic device architecture3000is illustrated as including the ALU3020, the electronic device architecture3000is not limited, and may contain additional and/or alternative processing circuitry. The memory unit3010may include a main memory and a cache memory. The electronic device architecture (chip)3000may be an on-chip memory processing unit.

The memory unit3010, the ALU3020, and/or the control unit3030may each independently include the above-described compound.

Referring toFIG.11, a cache memory1510, an ALU1520, and a control unit1530may form a central processing unit (CPU)1500, and the cache memory1510may include a static random access memory (SRAM). A main memory1600and an auxiliary storage1700may be provided apart from the CPU1500. The main memory1600may include a dynamic random access memory (DRAM) including layer structures such as those described above.

In some cases, an electronic device architecture may be implemented in a form in which unit computing devices and unit memory devices are adjacent to each other on a single chip without sub-units.

A method of preparing a dielectric material, according to one or more embodiment, may include: mechanically milling a mixture of a Nb compound, Na salt, a Sm compound, a M1-containing salt, and a M2-containing salt; and performing first heat treatment in an oxidizing atmosphere, thereby preparing the dielectric material including a compound represented by Formula 1:
(1−x−y)NaNbO3−xSm1/3NbO3−y(M1)a(M2)bO3[Formula 1]

wherein, in Formula 1, M1 may be a Group 1 element, a Group 2 element, or a Group 15 element, or a combination thereof; M2 may be a Group 4 transition metal element or a Group 5 transition metal element, or a combination thereof; and

0.1<x≤0.15, 0.001≤y≤0.1, 0<a<1, 0<b<1, and a+b=1.

FIG.4is a flowchart schematically showing a method of preparing a dielectric material according to at least one embodiment.

Referring toFIG.4, a mixture of a Nb compound, a Na salt, a Sm compound, a M1-containing salt, and a M2-containing salt is prepared. For example, in some example embodiments, the Nb compound may be niobium oxide; the Na salt may be sodium carbonate, sodium sulfate, or a combination thereof; the Sm compound may be a samarium oxide; and/or the M1-containing salt and M2-containing salt may each independently be barium carbonate, barium sulfate, strontium sulfate, calcium carbonate, calcium sulfate, sodium carbonate, sodium sulfate, bismuth carbonate, bismuth sulfate, or a combination thereof. Though not illustrated, in some example embodiments, the mixture may further include a Ti compound. For example, the Ti compound may be titanium oxide.

The amounts of the Nb compound, the Na salt, the Sm compound, the M1-containing salt, the M2-containing salt, and/or the Ti compound may be stoichiometrically controlled so as to obtain the compound represented by Formula 1.

Next, the mixture is mechanically milled. The mechanical milling may be ball milling, air-jet milling, bead milling, roll milling, hand milling, high-energy ball milling, planetary milling, stirred ball milling, vibrating milling, mechanofusion milling, shaker milling, attritor milling, disk milling, shape milling, nauta milling, nobilta milling, high-speed mixing, a combination thereof, and/or the like. In some example embodiments, the mechanical milling may be and/or include, for example, wet milling using a solvent. When the mechanical milling is performed by wet milling, a dielectric material with improved permittivity characteristics may be prepared.

In the wet milling using a solvent, a volatile solvent (e.g., with a low enthalpy of vaporization) such as ethanol and/or the like may be used as the solvent. Although the mechanical milling time varies according to milling conditions, the mechanical milling time may be, for example, about 1 hour to about 30 hours, for example, about 5 hours to about 25 hours.

The mechanically milled mixture is subjected to a first heat treatment in an oxidizing atmosphere. The first heat treatment may be performed at about 800° C. to about 1000° C. For example, the first heat treatment may be performed at about 850° C. to about 950° C. The first heat treatment may be performed for about 1 hour to about 30 hours, or for about 2 hours to about 15 hours. By the heat treatment under an oxidizing atmosphere in such time periods, the dielectric material may have further improved dielectric characteristics.

The method may further include, after the first heat treatment in the oxidizing atmosphere, obtaining a molded body using a product obtained from the first heat treatment; and performing second heat treatment on the molded product. The obtaining the molded body may, for example, include molding the product obtained from the first heat treatment, for example, by applying a uniaxial pressure to the product to produce a pellet. In some example embodiments, the molding may include, for example, a mold, but is not limited thereto.

The second heat treatment may be performed at about 1000° C. to about 1600° C. For example, the second heat treatment may be performed at about 1200° C. to about 1400° C. The second heat treatment may be performed for about 1 hour to about 30 hours, or for about 3 hours to about 25 hours. By the further inclusion of the second heat treatment under such conditions, defects of the dielectric material may be effectively prevented. For example, the second heat treatment may be used to anneal and/or sinter the dielectric material.

The first heat treatment (and/or second heat treatment) in an oxidizing atmosphere may be carried out under an atmosphere including oxygen, carbon dioxide, and/or the like. In an atmosphere containing oxygen, carbon dioxide, and/or the like, the amount of oxygen, carbon dioxide, and/or the like may be, for example, about 0.1% to about 21% by volume, about 0.1% to about 10% by volume, about 0.1% to about 5% by volume, about 0.1% to about 3% by volume, and/or about 0.5% to about 2% by volume of the total gas volume. The remainder gas, excluding oxygen, carbon dioxide, and/or the like, may be an inert gas. The inert gas may be argon, nitrogen, and/or the like, but is not limited thereto, and may be any inert gas used in the art.

In some example embodiments, the term “oxidizing atmosphere” may refer to, for example, an ambient air atmosphere.

The dielectric material prepared by the preparation method described above may have high permittivity and high specific resistivity and may also be stable at high temperatures.

One or more embodiments of the present disclosure will now be described in detail with reference to the following examples and comparative examples. However, these examples are only for illustrative purposes and are not intended to limit the scope of the present disclosure.

EXAMPLES

(Preparation of NaNbO3Binary Dielectric Material)

Reference Example 1

Nb2O5, Na2CO3, and Sm2O3were mixed in a reactor to obtain a mixture, and ethanol and zirconia balls were added thereto, and then ball-milled at room temperature in an air atmosphere for 24 hours to prepare a mixture. The prepared mixture was dried at 100° C. for 1 day to obtain dried powder. The amounts of Nb2O5, Na2CO3, and Sm2O3were stoichiometrically controlled so as to obtain the dielectric material as in Table 1.

The dried powder was put into an alumina crucible, and then subjected to a first heat treatment at 900° C. in an air atmosphere for 5 hours.

The first heat treatment product was pressed with uniaxial pressure to prepare pellets. The prepared pellets were secondarily heat-treated at 1300° C. in an atmosphere for 2 hours to prepare a dielectric material having a composition as represented in Table 1.

Reference Example 2

A dielectric material was prepared in the same manner as in Reference Example 1, except that stoichiometric amounts were controlled to be different from those of Example 1.

Comparative Reference Example 1

A dielectric material was prepared in the same manner as in Reference Example 1, except that the mixture was prepared using Gd2O3instead of Sm2O3, and the stoichiometric amounts were controlled so as to obtain the dielectric material as in Table 1 through second heat treatment at 125° C. for 2 hours.

Comparative Reference Example 2

A dielectric material was prepared in the same manner as in Reference Example 1, except that Y2O3was used instead of Sm2O3, and the stoichiometric amounts were controlled so as to obtain the dielectric material as in Table 1.

Comparative Reference Example 3

A dielectric material was prepared in the same manner as in Reference Example 1, except that La2O3was used instead of Sm2O3, and the stoichiometric amounts were controlled to be so as to obtain the dielectric material as in Table 1.

Comparative Reference Example 4

A dielectric material was prepared in the same manner as in Reference Example 1, except that Yb2O3was used instead of Sm2O3, and the stoichiometric amounts were controlled so as to obtain the dielectric material as in Table 1.

Comparative Reference Example 5

A dielectric material was prepared in the same manner as in Reference Example 1, except that Dy2O3was used instead of Sm2O3, and the stoichiometric amounts were controlled so as to obtain the dielectric material as in Table 1.

Comparative Reference Examples 6 to 8

A dielectric material was prepared in the same manner as in Reference Example 1, except that the stoichiometric amounts of Nb2O5, Na2CO3, and Sm2O3were controlled to be different from those of Example 1, so as to obtain the dielectric material as in Table 1.

TABLE 1ExampleComposition of NaNbO3binary dielectric materialReference0.85NaNbO3-0.15Sm1/3NbO3Example 1Reference0.90NaNbO3-0.10Sm1/3NbO3Example 2Comparative0.85NaNbO3-0.15Gd1/3NbO3ReferenceExample 1Comparative0.85NaNbO3-0.15Y1/3NbO3ReferenceExample 2Comparative0.85NaNbO3-0.15La1/3NbO3ReferenceExample 3Comparative0.85NaNbO3-0.15Yb1/3NbO3ReferenceExample 4Comparative0.85NaNbO3-0.15Dy1/3NbO3ReferenceExample 5Comparative0.95NaNbO3-0.05Sm1/3NbO3ReferenceExample 6Comparative0.80NaNbO3-0.20Sm1/3NbO3ReferenceExample 7Comparative0.75NaNbO3-0.25Sm1/3NbO3ReferenceExample 8
(Preparation of NaNbO3Ternary Dielectric Material)

Example 1

Nb2O5, Na2CO3, Sm2O3, BaCO3, and TiO2were mixed in a reactor to obtain a mixture, and ethanol and zirconia balls were added thereto, and then ball-milled at room temperature in an air atmosphere for 24 hours to prepare a mixture. The prepared mixture was dried at 100° C. for 1 day to obtain dried powder. The amounts of Nb2O5, Na2CO3, Sm2O3, BaCO3, and TiO2were stoichiometrically controlled in order to prepare a dielectric material as represented in Table 2.

The dried powder was put into an alumina crucible, and then subjected to first heat treatment at 900° C. in an air atmosphere for 5 hours.

The first-heat treatment product was pressed with uniaxial pressure to prepare pellets. The prepared pellets were pressed at a cold isotactic pressure (CIP) of 200 MPa for 3 minutes to obtain a molded body.

The molded body was secondarily heat-treated at 1300° C. in an air atmosphere for 2 hours to prepare a dielectric material having a composition as represented in Table 2.

Example 2

A dielectric material was prepared in the same manner as in Example 1, except that SrCO3was used instead of BaCO3, and the stoichiometric amounts were controlled so as to obtain the dielectric material as in Table 2.

Example 3

A dielectric material was prepared in the same manner as in Example 1, except that CaCO3was used instead of BaCO3, and the stoichiometric amounts were controlled so as to obtain a dielectric material as in Table 2.

Examples 4 and 5

Dielectric materials were prepared in the same manner as in Example 1, except that Na2CO3and Ta2O5were used instead of BaCO3and TiO2, respectively, to prepare dielectric materials as in Table 2.

Comparative Example 1

A dielectric material was prepared in the same manner as in Example 1, except that the stoichiometric amounts of Nb2O5, Na2CO3, Sm2O3, BaCO3, and TiO2were controlled to be different from those of Example 1, so as to obtain a dielectric material as in Table 2.

Comparative Example 2

A dielectric material was prepared in the same manner as in Example 1, except that SrCO3was used instead of BaCO3, and the stoichiometric amounts were controlled to be different from those of Example 2, so as to obtain a dielectric material as in Table 2.

Comparative Example 3

A dielectric material was prepared in the same manner as in Example 1, except that CaCO3was used instead of BaCO3, and the stoichiometric amounts were controlled to be different from those of Example 3, so as to obtain a dielectric material as in Table 2.

TABLE 2ExampleComposition of NaNbO3ternary dielectric materialExample 10.83NaNbO3-0.15Sm1/3NbO3-0.02BaTiO3Example 20.83NaNbO3-0.15Sm1/3NbO3-0.02SrTiO3Example 30.83NaNbO3-0.15Sm1/3NbO3-0.02CaTiO3Example 40.80NaNbO3-0.15Sm1/3NbO3-0.05NaTaO3Example 50.75NaNbO3-0.15Sm1/3NbO3-0.1NaTaO3Comparative0.81 NaNbO3-0.15Sm1/3NbO3-0.04BaTiO3Example 1Comparative0.81 NaNbO3-0.15Sm1/3NbO3-0.04SrTiO3Example 2Comparative0.81 NaNbO3-0.15Sm1/3NbO3-0.04CaTiO3Example 3

Evaluation Example 1: X-Ray Diffraction Test

X-ray diffraction spectra (XRD) of the NaNbO3binary dielectric materials of Reference Example 1, Reference Example 2, Comparative Reference Example 6, and Comparative Reference Example 7, which have different Sm1/3NbO3molar ratios, were measured with Cu Kα radiation. Using a D8 Advance, XRD spectrum analysis was performed on the powder obtained by grinding the pellets of each dielectric material. The results are shown inFIG.1.

Referring toFIG.1, the NaNbO3binary dielectric materials of Reference Example 1, Reference Example 2, Comparative Reference Example 6, and Comparative Reference Example 7 were all found to have a single phase and an orthorhombic phase but did not form a secondary phase.

Evaluation Example 2: Dielectric characteristic, specific resistivity characteristic, and temperature characteristic of NaNbO3binary dielectric materials

Dielectric characteristic, specific resistivity characteristic, and temperature characteristic of each NaNbO3binary dielectric material were evaluated according to the following methods. The results are shown in Tables 3 and 4 andFIG.2. Table 1 shows the results of evaluation of the dielectric characteristic, specific resistivity characteristic, and temperature characteristic of each of the NaNbO3binary dielectric materials of Reference Example 1 and Comparative Reference Example 1 to Comparative Reference Example 5 in which different rare earth elements were substituted into Na site of NaNbO3. Table 2 shows the results of evaluation of the dielectric characteristic, specific resistivity characteristic, and temperature characteristic of each of the NaNbO3binary dielectric materials of Reference Example 1, Reference Example 2, and Comparative Reference Example 6 to Comparative Reference Example 8 that were prepared in different Sm1/3NbO3molar ratios.FIG.2shows the results of changes in dielectric constant with respect to temperature of the NaNbO3binary dielectric materials of Reference Example 1 and Comparative Reference Examples 2 to 5.

(1) Grain Size and Relative Density

The grain size of each dielectric material was measured using a scanning electron microscope (SEM, S-5500, Hitachi, Ltd.). The relative density of each dielectric material was measured using a buoyancy method (e.g., the Archimedes method) as a relative density with respect to the density of 100% when no pores exist.

(2) Nominal Permittivity (Er, Tan δ)

Silver (Ag) was coated on the opposite surfaces of the dielectric pellets to form electrodes, and then permittivity was measured at room temperature (25° C.) using an E4980A Precision LCR Meter (Keysight) at an AC voltage of 1 V and a frequency of 1 kHz.

In Table 3, Er denotes permittivity, and tan δdenotes loss factor.

(3) Temperature Characteristic

To determine the temperature characteristic (e.g., the temperature coefficient of capacitance (TCC)), capacitance was measured at temperatures from −55° C. to 200° C. at 5° C. intervals in a temperature-controlled chamber with reference to X9S of the EIA specification. The temperature characteristic is represented by Equation 1.
TCC (%)=[(C−CRT/CRT]×100  [Equation 1]

wherein, in Equation 1, C is a capacitance value measured within a temperature range of −55° C. to 200° C., and CRTis a capacitance value measured at 25° C.

(4) Vacuum Permittivity (ε0), Effective Permittivity (ε), and Permittivity Change Rate (Δε/ε0)

Using Premier II Ferroelectric Tester (Radiant Technologies, Inc.) measurement was performed under the condition of applying a DC electric field of 0 kV/μm or 87 kV/μm and using an AC electric field of 87 mV/μm at a frequency of 1 kHz.

The permittivity change rate (Δε/ε0) is represented by Equation 2. In Tables 3 and 4, values obtained by multiplying the permittivity change rate by 100 are shown.
Δε/ε0=(ε−ε0)/ε0[Equation 2]

wherein, in Equation 2, ε is a permittivity at dc=8.7 kV/μm, i.e., an effective permittivity, and ε0is a permittivity at dc=0 kV/μm.

(5) Specific Resistivity (ρ)

Using Premier II Ferroelectric Tester (Radiant Technologies, Inc.) specific resistivity was measured for 1 second at a frequency of 1 kHz after stabilization for 60 seconds, under the condition of applying a DC high-electric field (87 kV/μm).

TABLE 3NominalΔε/SpecificTemperatureRelativepermittivityε0εε0×resistivitycharacteristicdensity(@ 1 kHz)(@ 1(@ 1100(ρ)TCCExample(%)εrtanδkHz)kHz)(%)(Ωcm)(%)Reference>997600.876056625.51.7 × 1012−5~4Example 1Comparative>991,4091.21,34987635.11.3 × 1012−22~0ReferenceExample 1Comparative>991,4031.91,4221,030288.0 × 1011−27~14ReferenceExample 2Comparative>994110.54954695.35.7 × 1011−4~31ReferenceExample 3Comparative>991,3371.61,42794234.06.5 × 1011−32~3ReferenceExample 4Comparative>991,4251.81,56296238.44.4 × 1011−35~5ReferenceExample 5

TABLE 4NominalΔε/SpecificTemperatureGrainRelativepermittivityε0εε0×resistivitycharacteristicsizedensity(@ 1 kHz)(@ 1(@ 1100(ρ)TCCExample(μm)(%)εrtanδkHz)kHz)(%)(Ωcm)(%)Reference1.2>997600.876056625.51.7 × 1012−5~4Example 1Reference0.96>996691.358549215.99.9 × 1011−10~15Example 2Comparative1.0>994421.641536711.65.5 × 1011−10~67ReferenceExample 6Comparative1.3>991.1050.61,22596821.01.2 × 1012−36~14ReferenceExample 7Comparative1.3>997410.383967120.01.9 × 1012−28~14ReferenceExample 8

Referring to Table 3, the nominal permittivity (ε) and the vacuum permittivity (ε0) at 1 kHz of the NaNbO3binary dielectric material of Reference Example 1 in which Sm was substituted into the Na site of NaNbO3were 760, and a specific resistivity (ρ) thereof was 1.7×1012Ωcm. In comparison, the nominal permittivity (εr) and the vacuum permittivity (ε0) at 1 kHz of the NaNbO3binary dielectric material of Comparative Reference Example 3 in which La was substituted into the Na site of NaNbO3were as low as 411 and 495, respectively. The specific resistivities (ρ) of the NaNbO3binary dielectric materials of Comparative Reference Example 2 to Comparative Reference Example 5 in which Y, La, Yb, and Dy were respectively substituted into the Na site of NaNbO3were as low as 8.0×1011Ωcm, 5.7×1011Ωcm, 6.5×1011Ωcm, and 4.4×1011Ωcm, respectively. The nominal permittivity (tan δ) at 1 kHz of NaNbO3binary dielectric material of Reference Example 1 was 0.8. In comparison, the nominal permittivities (tan δ) of the NaNbO3binary dielectric materials of Comparative Reference Examples 1, 2, 4, and 5 in which Gd, Y, Yb, and Dy were respectively substituted into the Na site of NaNbO3were relatively high at 1.2, 1.9, 1.6, and 1.8, respectively.

Referring to Table 3 andFIG.2, for the NaNbO3binary dielectric material of Reference Example 1, the temperature characteristic (TCC) in the range of −55° C. to +200° C. was stable at −5% to 4%. In comparison to this, the temperature characteristics (TCC) in the range of −55° C. to +200° C. of the NaNbO3binary dielectric materials of Comparative Reference Examples 1 to 5 were relatively unstable at −22% to 0%, −27% to 14%, −4% to 31%, −32% to 3%, and −35% to 5%, respectively.

From these results, it can be confirmed that the NaNbO3binary dielectric material of Reference Example 1 in which Sm was substituted at Na site of NaNbO3had excellent dielectric characteristic and specific resistivity characteristic and stable temperature characteristic (TCC), compared to the NaNbO3binary dielectric materials of Comparative Reference Example 1 to Comparative Reference Example 5.

Referring to Table 4, the NaNbO3binary dielectric materials of Reference Example 1 and Reference Example 2 in which 0.10 mol % and 0.15 mol % of Sm were respectively substituted into the Na site of NaNbO3had higher nominal permittivity (ε) and vacuum permittivity (ε0) than those of the NaNbO3binary dielectric material of Comparative Reference Example 6 in which 0.05 mol % of Sm was substituted into the Na site of NaNbO3. The NaNbO3binary dielectric material of Reference Example 1 had a higher specific resistivity (ρ) than that of the NaNbO3binary dielectric material of Comparative Reference Example 6.

The temperature characteristics (TCC) in the range of −55° C. to +200° C. of the NaNbO3binary dielectric materials of Reference Example 1 and Reference Example 2 were stable at −5% to 4% and −10% to 15%, respectively. In comparison, the temperature characteristics (TCC) in the range of −55° C. to +200° C. of the NaNbO3binary dielectric materials of Comparative Reference Examples 6 to 8 in which 0.05 mol %, 0.20 mol %, and 0.25 mol % of Sm were respectively substituted into the Na site of NaNbO3were relatively unstable, at −10% to 67%, −36% to 14%, and −28% to 14%, respectively.

From these results, it can be confirmed that the NaNbO3binary dielectric materials of Reference Example 1 and Reference Example 2 in which 0.10 mol % and 0.15 mol % of Sm were respectively substituted at Na site of NaNbO3had excellent dielectric characteristic and stable temperature characteristic (TCC), compared to the NaNbO3binary dielectric materials of Comparative Reference Example 6 to Comparative Reference Example 8.

Evaluation Example 3: Dielectric characteristic and temperature characteristic of NaNbO3ternary dielectric material.

The dielectric characteristics and temperature characteristics of the NaNbO3ternary dielectric materials of Examples 1 to Example 5 and Comparative Examples 1 to Comparative Example 3 were evaluated using the same methods as applied to the evaluation of effective permittivity (ε), nominal permittivity (tan δ), and temperature characteristic in Evaluation Example 2. The results are shown in Table 5 andFIG.3.FIG.3shows results showing dielectric constants and temperature characteristics of the NaNbO3binary dielectric materials or NaNbO3ternary dielectric materials of Reference Example 1, Examples 1 to 5, and Comparative Examples 1 to 3.

TABLE 5Nominal permittivity(@Temperatureε (@1 kHz)characteristic1 kHz)(tanδ)(TCC, %)Example 18500.8−5~8Example 21,0201.5−15~14Example 39200.8−14~13Example 49901.4−5~14Example 58601.7−5~15Comparative7200.5−2~24Example 1Comparative1,1302.1−28~16Example 2Comparative1,0100.6−28~18Example 3

Referring to Table 5 andFIG.3, the NaNbO3ternary dielectric materials of Examples 1 to 5 had an excellent effective permittivity (ε) of 850 or more, and a stable temperature characteristic (TCC) at −15% to 15%. In comparison, the temperature characteristics (TCC) of the NaNbO3ternary dielectric materials of Comparative Example 1 to Comparative Example 3 were relatively unstable. In addition, the nominal permittivity (tan δ) of the NaNbO3ternary dielectric material of Comparative Example 2 was higher, compared to the NaNbO3ternary dielectric materials of Examples 1 to 5.

From these results, it can be confirmed that the NaNbO3ternary dielectric materials of Example 1 to Example 5 had excellent dielectric characteristic and stable temperature characteristic (TCC).

As described above, according to the one or more embodiments, the dielectric material may include a NaNbO3ternary material having a permittivity (ε) of 600 or larger at 1 kHz, and a temperature coefficient of capacitance (TCC), expressed by Equation 1, of about −15% to about 15% in a range of about −55° C. to about +200° C. The NaNbO3ternary material may include a perovskite phase with a Sm element substituted into Na site. The dielectric material may be applied to high-temperature MLCCs for vehicles or special purposes, and also operate in a high-electric field region, and thus a device with high efficiency in accordance with thinning of the dielectric layer may be provided.

It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.