# Patent

## Title
Porcelain composition

## Abstract

A ceramic composition includes a glass composition and a filler including at least one of Al2O3 and TiO2, wherein the composition of the ceramic composition includes 0.15 to 0.55 mol of a, 0.45 to 0.85 mol of b, 0.01 to 0.2 mol of an oxide RO of an alkaline earth metal element R, and 0.1 to 0.4 mol of the filler, wherein a represents a molar quantity of an oxide Ln2O3 of a rare earth element Ln, b represents a molar quantity of boron oxide B2O3, and a+b=1 mol.

## Background
TECHNICAL FIELD
The present invention relates to ceramic compositions. In particular, it relates to a ceramic composition usable as, for example, a material for a multilayer substrate used for propagation of signals in a high-frequency band.
BACKGROUND ART
Recent years saw development in high-speed, large-capacity data communications and cellular communications. With respect to multilayer substrates having integrated circuits, this development led to not only size-reduction and increased density but also investigations as to use of signals having frequencies in a high-frequency band ranging from, for example, several ten megahertz to several hundred gigahertz. While ceramic compositions are used in these multilayer substrates, it is desirable that the ceramic compositions be made of a material (high-frequency band material) compatible with signals in the high-frequency band.
Typically, alumina (Al2O3) has been primarily used as the ceramic composition for the high-frequency band. As the density of the integrated circuits increases, there has been developed a process of making a multilayer substrate including an integrated circuit, the process including stacking a plurality of green sheets composed of unsintered Al2O3, each green sheet having a conductor paste that contains a material for metal wiring applied by printing, and then simultaneously baking the green sheets and the conductor paste. Since Al2O3 sinters at a temperature as high as 1,500° C. to 1,600° C., a high melting point-metal, such as tungsten or molybdenum, which can withstand such a high temperature, has been required as the material for the metal wiring of the integrated circuit.
The multilayer substrate has a problem in that it requires a large amount of energy since the sintering temperature is high, thereby increasing the manufacturing cost. Since the thermal expansion coefficient of Al2O3 is larger than that of the IC chip, such as a silicon chip, in the integrated circuit, the multilayer substrate may suffer from cracks depending on the operating temperature of the multilayer substrate. Furthermore, since the relative dielectric constant of Al2O3 is large, the rate of signal propagation in the integrated circuit has been low. Since the specific resistance of a high melting point-metal, such as tungsten or molybdenum, is large compared to that of Cu or Ag, which is suitable as a material for the metal wiring, the conductor loss due to the resistance of the metal wiring itself has also been large.
In view of the above, various ceramic compositions each in which a filler is incorporated in a glass composition have been developed as the material for multilayer substrates. Multilayer substrates using such ceramic compositions can be sintered at a temperature lower than that when Al2O3 is used. Thus, it becomes possible to simultaneously sinter the ceramic compositions and the material for metal wiring, such as Cu or Ag, having a smaller specific resistance. Furthermore, since the filler is contained in the glass composition, the change in shape of the ceramic composition can be reduced, and the strength of the ceramic composition can be increased.
For example, Japanese Examined Patent Application Publication No. 3-53269 described an example of such a ceramic composition, prepared by sintering a mixture of a CaO—SiO2—Al2O3—B2O3 glass composition and 50 to 35 mass % of Al2O3 as a filler at 800° C. to 1,000° C. Japanese Patent No. 3277169 discloses a ceramic composition containing 0 to 10 mol % of Al2O3 as a filler and a glass composition including 50 to 67 mol % of B2O3, 2 to 3 mol % of an oxide of an alkali metal element, 20 to 50 mol % of an oxide of an alkaline earth metal element, and 2 to 15 mol % of an oxide of a rare earth element. Japanese Unexamined Patent Application Publication No. 9-315855 discloses a ceramic composition containing an oxide of a rare earth element, Al2O3, CaO, and TiO2, and in which the compounding ratio of these components is limited within a particular range.
The performances required for the ceramic composition for the high-frequency band include a low dielectric loss tanδ in the high-frequency band and a small absolute value of the temperature coefficient τf of the resonant frequency.
In other words, the loss in the course of signal propagation in the high-frequency band is preferably as small as possible. Thus, it is desirable that the dielectric loss tanδ of the ceramic composition in the high-frequency band be small, i.e., that the Q value (1/tan δ) be large. Moreover, in order to yield stable performance from the ceramic composition serving as a dielectric member despite a temperature change, it is desirable that the absolute value of the temperature coefficient τf of the resonant frequency be small, i.e., that the temperature dependence of the resonant frequency be low.


DISCLOSURE OF INVENTION
Under the above-described circumstances, an object of the present invention is to provide a ceramic composition that can be sintered at a low temperature and has a small dielectric loss in the high-frequency band and a low temperature dependence of the resonant frequency.
An aspect of the present invention provides a ceramic composition including a glass composition and a filler incorporated in the glass composition, the filler including at least one of Al2O3 and TiO2, wherein the composition of the ceramic composition includes 0.15 to 0.55 mol of a, 0.45 to 0.85 mol of b, 0.01 to 0.2 mol of an oxide RO of an alkaline earth metal element R, and 0.1 to 0.4 mol of the filler, wherein a represents a molar quantity of an oxide Ln2O3 of a rare earth element Ln, b represents a molar quantity of boron oxide B2O3, and a+b=1 mol.
Preferably, the ceramic composition includes 0.05 mol or less of tungsten oxide WO3, wherein a represents a molar quantity of an oxide Ln2O3 of a rare earth element Ln, b represents a molar quantity of boron oxide B2O3, and a+b=1 mol.
Preferably, the ceramic composition includes 0.0005 to 0.002 mol of an oxide M2O of an alkali metal element M, wherein a represents a molar quantity of an oxide Ln2O3 of a rare earth element Ln, b represents a molar quantity of boron oxide B2O3, and a+b=1 mol.
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventor has conducted various studies on the composition in order to obtain a ceramic composition that can be sintered at a low temperature and has a small dielectric loss in the high-frequency band and a low temperature dependence of the resonant frequency.
It has been found that a ceramic composition in which a filler composed of an inorganic oxide is incorporated in a glass composition is most suitable as such a ceramic composition. The internal structure of the ceramic composition is a network structure composed of a glass composition filling the gaps between the respective particles of the filler. Since the material usable as the filler is limited within a certain range, the characteristics of the glass composition must be improved to further improve the performance.
Thus, the material for the glass composition was studied first. In particular, the sintering temperature of the glass composition, the compatibility with the filler, the relative dielectric constant, the dielectric loss in the high-frequency band, and the temperature dependence of the resonant frequency were investigated. Of these items, the dielectric characteristic was measured by a dielectric resonator method (short-circuited at both ends of a dielectric resonator), i.e., Hakki & Coleman method, using a cylindrical test sample after sintering.
In general, the dielectric loss is evaluated in terms of Q value, which is obtained by the sharpness of the resonance. The Q value is frequency-dependent and decreases in proportion to the frequency. In contrast, the resonant frequency changes with the shape and the dielectric constant of the test sample. Thus, the dielectric loss of the ceramic composition is evaluated by comparative assessment in terms of the product fQ of the resonant frequency fo and Q.
As a result of the studies on various glass compositions, it has been found that a glass composition containing a large amount of crystals obtained by mixing an oxide Ln2O3 of a rare earth element (also referred to as “Ln”) and boron oxide B2O3 exhibits a particularly low dielectric loss. In this glass composition, crystals of LnBO3, LnB3O6, Ln3BO3, or Ln4B2O9 appear depending on the compounding ratio, and the phase of these crystals presumably decreases the dielectric loss.
However, in order to adjust the composition of the glass composition composed of only two components, i.e., Ln2O3 and B2O3, to yield a low dielectric loss, the melting temperature must be increased, and thus, the sintering temperature required for obtaining a dense sinter becomes high. It was found that by adding an adequate amount of an oxide RO of an alkaline earth metal element R (wherein R represents at least one of Mg, Ca, Sr and Ba) to the composition composed of Ln2O3 and B2O3, the sintering temperature can be decreased without significantly affecting the dielectric loss.
Here, the target performance of the ceramic composition is set as follows: that the value fQ (fo [GHz]×Q) at around 10 GHz is 15,000 or higher; that the change in resonant frequency with temperature is small; and that the composition can be sintered at a temperature as low as 1,000° C. or less, which is the temperature at which metal wiring composed of a highly conductive material, Ag or Cu, can be simultaneously formed to produce a multilayer substrate. The investigations on the composition of the ceramic composition were carried out based these. That the change in resonant frequency with temperature be small is important for the stable operation of the integrated circuit. The resonant frequency was measured while varying the temperature, and the rate of change in resonant frequency (temperature characteristic τf) with the varying temperature was evaluated. The target range of the temperature characteristic τf of the resonant frequency was set to within ±50 ppm/° C. (−50 ppm/° C.≦τf≦+50 ppm/° C.).
It was also found that incorporation of tungsten oxide, WO3, was effective for decreasing the sintering temperature. It was found that when an excessively large amount of WO3 was incorporated, the change in resonant frequency with temperature tended to shift toward the negative side.
It was found that incorporation of a small amount of an oxide M2O of an alkali metal element M (wherein M represents at least one selected from Li, Na, and K) can further decrease the sintering temperature. In particular, incorporation of M2O can effectively decrease the sintering temperature when a process of mixing all the starting materials and then sintering the resulting mixture in one step to obtain a ceramic composition is employed.
The filler is important for maintaining the strength of the ceramic composition and the shape during the sintering. Here, one or both of Al2O3 and TiO2 are used as the filler. When the strength is desired, Al2O3 is primarily used whereas TiO2 is primarily used when a large dielectric constant is desired. However, when the amount of filler is excessively large, the sintering temperature must be increased. When the amount of the filler is excessively small, the strength and the shape can no longer be maintained. Thus, the amount of the filler is limited by these factors.
The present invention has been made based on these results of studies by specifically setting the limit of the composition range of the ceramic composition. The ceramic composition of the present invention includes a glass composition and a filler contained in the glass composition and is sintered at a low temperature. The reasons for limiting the amount of each component of the composition are as follows.
Where the content of the oxide Ln2O3 of the rare earth element Ln in the ceramic composition of the present invention is represented by a, the content of the boron oxide B2O3 in the ceramic composition of the present invention is represented by b, and a+b=1 mol, a is 0.15 to 0.55 mol and b is 0.45 to 0.85 mol.
These content ranges are necessary for decreasing the dielectric loss in the high-frequency band and for performing low-temperature sintering. When the contents of Ln2O3 and B2O3 are set as above, excellent dielectric characteristic, i.e., a high fQ value, can be yielded by the generation of crystals represented by LnxByOz (wherein x, y, and z each represent an integer). In other words, where a+b=1 mol and a is less than 0.15 and b is more than 0.85, B2O3 that cannot form LnxByOz enters a liquid phase, thereby increasing the glass phase. Thus, the dielectric loss cannot be decreased. Where a+b=1 mol and a is more than 0.55 and b is less than 0.45, the sintering temperature increases, and a ceramic composition composed of a dense sinter cannot be obtained by the target low-temperature sintering.
Note that any of the rare earth elements represented by Ln can increase the fQ value. Thus, in this invention, one or more rare earth elements can be selected. In particular, when La and/or Nd is used as the rare earth element, an fQ value higher than that achieved by other rare earth elements can be obtained. However, the sintering temperature and the dielectric constant of the ceramic composition differ depending on the type of rare earth element. Thus, these properties may be adequately adjusted by changing the type of the rare earth element or by changing the content of the oxide RO of the alkaline earth metal element R described below.
The content of the each component described below is indicated in terms of a molar ratio with respect to one mole of the total of Ln2O3 and B2O3.
The content of the oxide RO of the alkaline earth metal element R is 0.01 to 0.2 mol. At an RO content less than 0.01 mol, the sintering temperature cannot be decreased. At an RO content exceeding 0.2 mol, the temperature characteristic τf of the resonant frequency becomes lower than −50 ppm/° C., i.e., excessively shifted toward the negative side, thereby increasing the temperature dependence.
At least one of MgO, CaO, SrO, and BaO may be used as the oxide RO of the alkaline earth metal R. In particular, the fQ value tends to be larger with CaO compared to that with oxides of other alkaline earth metals.
Preferably, tungsten oxide WO3 is contained in the ceramic composition of the present invention. When WO3 is contained, a dense sinter can be obtained by low-temperature sintering, which is the target of the present invention, while increasing the fQ value. In order to achieve such an effect, WO3 is preferably contained in an amount of 0.05 mol or less and more preferably in an amount of 0.005 to 0.05 mol. At a WO3 content exceeding 0.05 mol, the fQ value decreases, and the temperature characteristic τf of the resonant frequency tends to significantly shift toward the negative side. When the WO3 content is less than 0.005 mol, the above-described effect is not easily achieved. In the present invention, WO3 is not an essential component.
The ceramic composition of the present invention preferably contains 0.0005 to 0.002 mol of an oxide M2O of an alkali metal element M. In this manner, the sintering temperature can be further decreased. In general, a glass composition containing alkali metal ions exhibits a large dielectric loss and a small fQ value due to ionic induction. At an M2O content of 0.002 mol or less, the fQ value is rarely affected. At an M2O content of 0.0005 mol or more, the sintering temperature tends to decrease.
One or both of Al2O3 and TiO2 in a total amount of 0.1 to 0.4 mol per mole of the total of Ln2O3 and B2O3 are contained as the filler. At a filler content less than 0.1 mol, excessive deformation may occur during sintering and the strength of the ceramic composition after the sintering may become insufficient. At a filler content exceeding 0.4 mol, the sintering temperature is increased, and it may be difficult to conduct low-temperature sintering at 1,000° C. or less. In order to increase the strength of the ceramic composition, Al2O3 may be singularly used or the content of Al2O3 may be increased. In order to increase the dielectric constant of the ceramic composition, TiO2 may be singularly used or the content of TiO2 may be increased.
There are mainly two methods as the method for producing the ceramic composition of the present invention. According to a first method, powders of starting materials for ceramic composition are prepared, and the powders are respectively weighed to yield a desired composition. The powders are wet-mixed in a ball mill, dried, and calcined at about 800° C. The resulting calcined material is pulverized to obtain a powder. A binder is added to the powder, and the resulting mixture is kneaded and formed into a desired shape to obtain a compact. The compact is heated to remove the binder and sintered to obtain the ceramic composition of the present invention.
According to a second method, powders of starting materials for the glass composition are prepared and respectively weighed to yield a desired composition. The powders are mixed with each other, and the resulting mixture is melted by heating at 1,000° C. or higher and rapidly cooled to produce a glass frit. The glass frit is pulverized. The filler was separately sintered and pulverized to prepare a powder. The glass frit, the filler, and the binder are mixed and kneaded, and formed into a compact. The binder is removed from the compact, and the resulting compact is sintered to prepare a ceramic composition of the present invention. In this second method, with respect to the glass frit containing Al2O3 and/or TiO2 serving as the filler, it is possible to mix and knead the filler and the binder.
The above-described compact can be sintered at a temperature as low as 800° C. to 1,000° C. At a sintering temperature less than 800° C., the sintering of the ceramic composition may not be insufficient, and density is not satisfactory. Thus, satisfactory strength may not be exhibited. When the ceramic composition of the present invention is used as a material for a multilayer substrate and is sintered simultaneously with the material for metal wiring, the material for the metal wiring may be heated to a temperature higher than the melting point and may start to melt. However, at a temperature or 1,000° C. or less, the sintering can be performed without melting the material for the metal wiring, such as Cu or Ag. It should be noted that when Cu is used as the material for metal wiring, a reducing atmosphere is preferable to avoid possible oxidation, and when Ag is used as the material for metal wiring, the sintering temperature is preferably up to 930° C.
The above-described materials for the ceramic composition are not necessarily oxides as long as they are contained in the ceramic composition by forming oxides after the sintering. Thus, for example, carbonate salts, such as CaCO3, and compounds, such as nitrides, e.g., BN, other than oxides may be used as the starting materials. Although these starting materials may contain impurities, they can be treated as single compounds as long as the impurity content is 5 mass % or less with respect to the mass of the respective compound and the same effects can be still be achieved.
In making a multilayer substrate having an integrated circuit by using the ceramic composition of the present invention, the material after kneading is first formed into sheets to prepare green sheets, and a conductive paste containing the material for metal wiring is applied on each green sheet by printing. A plurality of green sheets with the conductive paste applied thereon is stacked and sintered.
Here, a constraint sintering process in which the compact obtained by stacking a plurality of green sheets having the conductive paste applied thereon by printing is sintered while applying pressure or constraint in the vertical direction may be employed. According to this process, the contraction due to sintering is limited in the vertical direction, i.e., the Z direction, and no contraction occurs in the surface direction, i.e., the X-Y direction. A multilayer substrate having superior surface flatness can be accurately obtained as a result.
Preferably, green sheets composed of Al2O3 or the like that do not sinter at the sintering temperature of the ceramic composition are provided on the upper and lower surfaces, respectively, of the compact, and the compact is preferably sintered while applying pressure or constraint through these green sheets. Here, it is important that the Al2O3 green sheets on the upper and lower surfaces of the compact be easily separable and that the metal wiring after the sintering sufficiently adhere onto the ceramic composition so as to avoid conduction failure. Studies were conducted whether this process can be applied to the ceramic composition. The results confirmed that this process can be applied without any problem.
EXAMPLES
The starting material powders of the respective components were adequately weighed to give ceramic compositions having compositions shown in Tables 1 to 5. The starting material powders were all oxides. Deionized water was added to the starting material powders, and the resulting mixture was wet-mixed for 20 hours in a ball mill containing zirconia balls.
The resulting mixture was dried and calcined at 700° C. for 2 hours. The calcined mixture was pulverized to obtain a calcined powder. The calcined powder was combined with 10 mass % of a PVA aqueous solution serving as a binder, and the resulting mixture was kneaded, granulated, and press-formed into a compact having a diameter of 15 mm and a height of 7.5 mm. However, Samples 60, 61, and 62 shown in Table 3 were prepared by melting the materials excluding the filler by heating to 1,300° C., rapidly cooling the resulting materials to form a glass frit, adding a predetermined amount of the filler to the glass frit, adding 10 mass % of a PVA aqueous solution serving as a binder to the resulting mixture, kneading and granulating the resulting mixture, and press-forming the resulting mixture into a compact having a diameter of 15 mm and a height of 7.5 mm.
These press-formed compacts were used as the samples. The temperature at which an experimental sintered compact prepared by sintering in the temperature range of 800° C. to 1,250° C. is sufficiently dense is selected, and each sample was sintered at the corresponding selected temperature. Sintering of the sample was conducted after the sample was heated in air at 500° C. to 600° C. to remove the binder. The sintering of the sample was conducted by heating the sample at the above-described selected temperature for 2 hours.
The resulting cylindrical sinters were each polished to prepare a flat and smooth setter surface and then analyzed by a dielectric resonator method (short-circuited at both ends of a dielectric resonator) to determine the relative dielectric constant εr and the Q value (Q=1/tan δ). Since the dielectric loss varies depending on the measurement resonant frequency fo, the dielectric loss was evaluated in terms of the fQ value, which is a product of fo and Q and is a constant value dependent on the material of the sample but independent from the frequency. The temperature characteristic τf of the resonance frequency was determined from the rate of change in resonant frequency with varying temperature with reference to the resonant frequency fo at 25° C. The results of the measurement are shown in Tables 1 to 5.









TABLE 1









Composition of ceramic composition (molar ratio)














Ln2O3

RO

M2O



Sample
(Ln: Rare earth

(R: Alkaline earth

(M: Alkali metal
Filler


No.
element)
B2O3
metal element)
WO3
element)
(Al2O3 or TiO2)





 1
La2O3: *0.1000
*0.9000 
CaO: 0.0500
0.0100
0
Al2O3: 0.2000


 2
La2O3: 0.1500
0.8500
CaO: 0.0500
0.0100
0
Al2O3: 0.2000


 3
La2O3: 0.2500
0.7500
CaO: 0.0500
0.0100
0
Al2O3: 0.2000


 4
La2O3: 0.3333
0.6667
CaO: 0.0500
0.0100
0
Al2O3: 0.2000


 5
La2O3: 0.4000
0.6000
CaO: 0.0500
0.0100
0
Al2O3: 0.2000


 6
La2O3: 0.5000
0.5000
CaO: 0.0500
0.0100
0
Al2O3: 0.2000


 7
La2O3: *0.6000
*0.4000 
CaO: 0.0500
0.0100
0
Al2O3: 0.2000


 8
La2O3: *0.6667
*0.3333 
CaO: 0.0500
0.0100
0
Al2O3: 0.2000


 9
La2O3: 0.2500
0.7500
*0
0.0100
0
Al2O3: 0.2000


10
La2O3: 0.2500
0.7500
CaO: 0.0100
0.0100
0
Al2O3: 0.2000


11
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
Al2O3: 0.2000


12
La2O3: 0.2500
0.7500
CaO: 0.2000
0.0100
0
Al2O3: 0.2000


13
La2O3: 0.2500
0.7500
CaO: *0.2500
0.0100
0
Al2O3: 0.2000


14
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
Al2O3: 0.2000


15
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
Al2O3: 0.2000


16
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0300
0
Al2O3: 0.2000


17
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0500
0
Al2O3: 0.2000


18
La2O3: 0.2500
0.7500
CaO: 0.1000
*0.0700 
0
Al2O3: 0.2000


19
La2O3: 0.2500
0.7500
CaO: 0.1000
*0.1000 
0
Al2O3: 0.2000


20
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
Al2O3: 0.1000


21
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
Al2O3: 0.3000


22
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
Al2O3: 0.4000


23
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
Al2O3: 0.5500


24
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
Al2O3: 0.6000


25
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
Al2O3: 0.1000













Characteristics of ceramic composition


















Relative

Temperature






Sintering
dielectric

characteristic
Resonant



Sample
temperature
constant
fQ
τf
frequency



No.
(° C.)
εr
(GHz)
(ppm/° C.)
f0 (GHz)
Remarks







 1
800
9.1
7500
−41
13.5
Comparative Example



 2
825
9.5
16500
−36
13.2
Invention Example



 3
850
10.1
15600
−35
13.0
Invention Example



 4
850
10.0
16000
−20
12.0
Invention Example



 5
900
11.0
17500
−15
12.9
Invention Example



 6
950
11.5
21000
−17
12.7
Invention Example



 7
1200 
11.8
10200
−25
12.4
Comparative Example



 8
1250 
10.3
15000
−20
13.5
Comparative Example



 9
1150 
11.8
17000
−25
12.0
Comparative Example



10
1000 
11.5
17500
−30
11.7
Invention Example



11
950
11.7
17200
−37
11.2
Invention Example



12
900
11.4
16800
−42
11.4
Invention Example



13
950
10.2
15800
−73
13.1
Comparative Example



14
900
11.8
16800
−31
11.4
Invention Example



15
900
10.0
17200
−31
12.7
Invention Example



16
850
10.2
18500
−35
12.4
Invention Example



17
850
10.1
17500
−39
12.8
Invention Example



18
850
9.8
7200
−59
13.1
Comparative Example



19
850
9.8
4300
−70
13.1
Comparative Example



20
850
9.2
17400
−32
12.2
Invention Example



21
900
9.1
18000
−37
13.0
Invention Example



22
950
8.5
18100
−38
13.9
Invention Example



23
1100 
7.8
12000
−29
14.0
Comparative Example



24
1150 
7.1
9500
−13
14.1
Comparative Example



25
910
10.0
16500
−31
12.1
Invention Example







Asterisks indicate that the marked features are outside the scope of the present invention.















TABLE 2









Composition of ceramic composition (molar ratio)














Ln2O3 

RO

M2O



Sample
(Ln: Rare earth

(R: Alkaline earth

(M: Alkali metal
Filler


No.
element)
B2O3
metal element)
WO3
element)
(Al2O3 or TiO2)





26
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
TiO2: 0.3000


27
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
TiO2: 0.4000


28
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
0
TiO2: *0.5000


29
Nd2O3: *0.1000
*0.9000
CaO: 0.1000
0
0
Al2O3: 0.1500


30
Nd2O3: 0.1500
0.8500
CaO: 0.1000
0
0
Al2O3: 0.1500


31
Nd2O3: 0.2500
0.7500
CaO: 0.1000
0
0
Al2O3: 0.1500


32
Nd2O3: 0.3300
0.6700
CaO: 0.1000
0
0
Al2O3: 0.1500


33
Nd2O3: 0.4000
0.6000
CaO: 0.1000
0
0
Al2O3: 0.1500


34
Nd2O3: 0.5000
0.5000
CaO: 0.1000
0
0
Al2O3: 0.1500


35
Nd2O3: 0.5500
0.4500
CaO: 0.1000
0
0
Al2O3: 0.1500


36
Nd2O3: *0.6000
*0.4000
CaO: 0.1000
0
0
Al2O3: 0.1500


37
La2O3: 0.1000
0.8000
CaO: 0.1000
0
0
Al2O3: 0.1500



Nd2O3: 0.1000


38
La2O3: 0.2000
0.6000
CaO: 0.1000
0
0
Al2O3: 0.1500



Nd2O3: 0.2000


39
La2O3: 0.3000
0.5000
CaO: 0.1000
0
0
Al2O3: 0.1500



Nd2O3: 0.2000


40
La2O3: 0.3000
0.5000
CaO: 0.1000
0
0
Al2O3: 0.1500



Nd2O3: 0.2000


41
La2O3: *0.3000
*0.4000
CaO: 0.1000
0
0
Al2O3: 0.1500



Nd2O3: *0.3000


42
La2O3: 0.3333
0.6667
BaO: 0.1000
0
0
Al2O3: 0.1500


43
La2O3: 0.3333
0.6667
BaO: 0.1000
0
0
Al2O3: 0.1500


44
La2O3: 0.3333
0.6667
BaO: *0.2500
0
0
Al2O3: 0.1500


45
La2O3: 0.3333
0.6667
SrO: 0.0100
0
0
Al2O3: 0.1500













Characteristics of ceramic composition


















Relative

Temperature






Sintering
dielectric

characteristic
Resonant



Sample
temperature
constant
fQ
τf
frequency



No.
(° C.)
εr
(GHz)
(ppm/° C.)
f0 (GHz)
Remarks







26
915
12.1
17200
−25
12.4
Invention Example



27
950
14.1
15000
−20
11.8
Invention Example



28
1125
14.3
9300
−25
11.1
Comparative Example



29
850
9.3
7200
−36
13.8
Comparative Example



30
900
10.2
16800
−39
12.4
Invention Example



31
925
10.8
17500
−30
12.1
Invention Example



32
925
11.0
16000
−25
11.0
Invention Example



33
950
12.0
18000
−20
11.2
Invention Example



34
950
11.8
17500
−15
11.5
Invention Example



35
950
11.5
15200
−14
11.7
Invention Example



36
1050
10.1
11300
−21
10.9
Comparative Example



37
900
10.5
17500
−30
12.2
Invention Example



38
950
11.8
18000
−18
11.9
Invention Example



39
900
11.7
17000
−14
11.6
Invention Example



40
900
11.8
18000
−13
11.5
Invention Example



41
1025
9.8
6300
−21
14.3
Comparative Example



42
950
10.6
15600
−35
10.1
Invention Example



43
1000
11.0
15000
−45
11.0
Invention Example



44
950
11.5
16200
−71
11.1
Comparative Example



45
1000
9.9
15000
−38
10.2
Invention Example







Asterisks indicate that the marked features are outside the scope of the present invention.















TABLE 3









Composition of ceramic composition (molar ratio)














Ln2O3 

RO

M2O



Sample
(Ln: Rare earth

(R: Alkaline earth

(M: Alkali metal
Filler


No.
element)
B2O3
metal element)
WO3
element)
(Al2O3 or TiO2)





46
La2O3: 0.3333
0.6667
SrO: 0.1000
0
0
Al2O3: 0.1500


47
La2O3: 0.3333
0.6667
SrO: *0.2500
0
0
Al2O3: 0.1500


48
La2O3: 0.3333
0.6667
CaO: 0.0500
0
0
Al2O3: 0.1500





BaO: 0.0100


49
La2O3: 0.3333
0.6667
CaO: 0.1000
0
0
Al2O3: 0.1500





BaO: 0.0500


50
La2O3: 0.3333
0.6667
CaO: 0.1000
0
0
Al2O3: 0.1500





SrO: 0.0500


51
La2O3: 0.3333
0.6667
BaO: 0.0100
0
0
Al2O3: 0.1500





SrO: 0.0500


52
La2O3: 0.2500
0.7500
CaO: 0.1000
0
Li2O: 0.0010
Al2O3: 0.1500


53
La2O3: 0.2500
0.7500
CaO: 0.1000
0
Li2O: 0.0020
Al2O3: 0.1500


54
La2O3: 0.2500
0.7500
CaO: 0.1000
0
Li2O: *0.0025
Al2O3: 0.1500


55
La2O3: 0.2500
0.7500
BaO: 0.0100
0
Li2O: 0.0010
Al2O3: 0.1500


56
La2O3: 0.3333
0.6667
SrO: 0.1000
0
Li2O: 0.0010
Al2O3: 0.1500


57
La2O3: 0.3333
0.6667
CaO: 0.1000
0
Na2O: 0.0010
Al2O3: 0.1500


58
La2O3: 0.3333
0.6667
CaO: 0.1000
0
Na2O: 0.0020
Al2O3: 0.1500


59
La2O3: 0.3333
0.6667
CaO: 0.1000
0
Na2O: *0.0025
Al2O3: 0.1500


60
La2O3: 0.3333
0.6667
CaO: 0.1000
0
Li2O: 0.0010
Al2O3: 0.1500







Na2O: 0.0010


61
La2O3: 0.3333
0.6667
CaO: 0.1000
0
Li2O: 0.0010
Al2O3: 0.1500







K2O: 0.0010


62
La2O3: 0.3333
0.6667
CaO: 0.1000
0
K2O: 0.0010
Al2O3: 0.1500







Na2O: 0.0010













Characteristics of ceramic composition
















Relative

Temperature





Sintering
dielectric

characteristic
Resonant


Sample
temperature
constant
fQ
τf
frequency


No.
(° C.)
εr
(GHz)
(ppm/° C.)
f0 (GHz)
Remarks





46
1000 
10.2
15000
−35
10.2
Invention Example


47
950
10.8
12500
−70
10.2
Comparative Example


48
980
11.0
15200
−45
10.2
Invention Example


49
980
11.5
15000
−38
9.8
Invention Example


50
950
10.2
15000
−35
10.0
Invention Example


51
980
11.5
15000
−40
10.1
Invention Example


52
900
11.7
14500
−38
9.8
Invention Example


53
850
9.8
15500
−40
8.0
Invention Example


54
800
6.8
<2000
Immeasurable
7.8
Comparative Example


55
900
12.0
15100
−35
10.1
Invention Example


56
850
11.0
15300
−39
10.5
Invention Example


57
850
10.2
15000
−35
11.3
Invention Example


58
800
8.0
15100
−36
12.1
Invention Example


59
800
5.0
<2000
Immeasurable
15.8
Comparative Example


60
**800 
8.5
16100
−38
11.8
Invention Example


61
**825 
8.8
15000
−40
11.6
Invention Example


62
**825 
9.0
15500
−38
11.3
Invention Example





Asterisks indicate that the marked features are outside the scope of the present invention.


Double asterisks indicate that the filler was mixed after preparation of the glass frit, and the resulting mixture was then sintered.















TABLE 4









Composition of ceramic composition (molar ratio)














Ln2O3

RO

M2O



Sample
(Ln: Rare earth

(R: Alkaline earth

(M: Alkali metal
Filler


No.
element)
B2O3
metal element)
WO3
element)
(Al2O3 or TiO2)





63
La2O3: 0.3333
0.6667
CaO: 0.1000
0
Rb2O: 0.0010
Al2O3: 0.1500


64
La2O3: 0.3333
0.6667
CaO: 0.1000
0
Cs2O: 0.0010
Al2O3: 0.1500


65
La2O3: 0.3333
0.6667
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.1500


66
La2O3: 0.3333
0.6667
CaO: 0.1000
0.0300
Li2O: 0.0010
Al2O3: 0.1500


67
La2O3: 0.3333
0.6667
CaO: 0.1000
0.0500
Li2O: 0.0010
Al2O3: 0.1500


68
La2O3: 0.3333
0.6667
CaO: 0.1000
*0.0600
Li2O: 0.0010
Al2O3: 0.1500


69
Nd2O3: 0.3333
0.6667
CaO: 0.1000
0.0300
Li2O: 0.0010
Al2O3: 0.1500


70
Nd2O3: 0.3333
0.6667
CaO: 0.1000
0.0500
Li2O: 0.0010
Al2O3: 0.1500


71
Nd2O3: 0.3333
0.6667
CaO: 0.1000
*0.0600
Li2O: 0.0010
Al2O3: 0.2000


72
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.1000








TiO2: 0.1000


73
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.2000








TiO2: 0.1000


74
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.2500








TiO2: 0.2500


75
Nd2O3: 0.2500
0.7500
CaO: 0.0500
0.0100
Li2O: 0.0010
Al2O3: 0.2000





BaO: 0.0500


76
La2O3: 0.2000
0.6000
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.1000



Nd2O3: 0.2000

BaO: 0.0500

Na2O: 0.0010
TiO2: 0.1000


77
La2O3: 0.1500
0.7000
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.3000



Nd2O3: 0.1500

BaO: 0.0500


78
La2O3: 0.2000
0.6667
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.1000



Nd2O3: 0.1333


79
La2O3: 0.2333
0.6667
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.1000



Nd2O3: 0.1000













Characteristics of ceramic composition


















Relative

Temperature






Sintering
dielectric

characteristic
Resonant



Sample
temperature
constant
fQ
τf
frequency



No.
(° C.)
εr
(GHz)
(ppm/° C.)
f0 (GHz)
Remarks







63
850
8.7
15000
−35
12.1
Invention Example



64
850
8.5
15000
−33
13.0
Invention Example



65
850
10.2
16000
−40
12.0
Invention Example



66
850
7.8
15500
−45
13.8
Invention Example



67
850
7.0
15000
−49
13.5
Invention Example



68
800
6.8
9500
−65
14.0
Comparative Example



69
850
7.5
16000
−41
13.8
Invention Example



70
800
6.8
15000
−48
13.3
Invention Example



71
800
6.3
6300
−68
14.3
Comparative Example



72
950
11.3
16800
−33
10.8
Invention Example



73
1000
13.1
17200
−35
10.2
Invention Example



74
1150
13.8
16000
−38
10.0
Comparative Example



75
1000
12.1
16000
−30
10.5
Invention Example



76
900
11.8
15800
−25
11.0
Invention Example



77
950
9.5
15000
−30
12.1
Invention Example



78
900
10.0
15500
−35
10.8
Invention Example



79
900
10.5
15000
−40
11.5
Invention Example







Asterisks indicate that the marked features are outside the scope of the present invention.















TABLE 5









Composition of ceramic composition (molar ratio)














Ln2O3 

RO

M2O



Sample
(Ln: Rare earth

(R: Alkaline earth

(M: Alkali metal
Filler


No.
element)
B2O3
metal element)
WO3
element)
(Al2O3 or TiO2)





80
La2O3: 0.3333
0.6667
CaO: 0.0500
0.0100
Li2O: 0.0010
Al2O3: 0.1000





BaO: 0.0500

Na2O: 0.0010


81
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.1000





SrO: 0.1000


82
La2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
Li2O: 0.0020
Al2O3: 0.1000


83
La2O3: 0.3333
0.6667
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.2000








TiO2: 0.2000


84
La2O3: 0.3333
0.6667
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: *0.3000








TiO2: *0.3000


85
Nd2O3: 0.2500
0.7500
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.3000


86
Nd2O3: 0.3333
0.6667
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.4000


87
Nd2O3: 0.5000
0.5000
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.3000


88
Nd2O3: 0.5000
0.5000
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.3000







K2O: 0.0010


89
Nd2O3: 0.5000
0.5000
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.3000





BaO: 0.1000


90
Nd2O3: 0.5000
0.5000
CaO: 0.1000
0.0200
Li2O: 0.0010
Al2O3: 0.3000





BaO: 0.1000


91
La2O3: 0.2500
0.5000
CaO: 0.1000
0.0500
Li2O: 0.0010
Al2O3: 0.3000



Nd2O3: 0.2500

BaO: 0.1000


92
La2O3: 0.3000
0.4500
CaO: 0.1000
0.0100
Li2O: 0.0010
Al2O3: 0.3000



Nd2O3: 0.2500

BaO: 0.1000













Characteristics of ceramic composition


















Relative

Temperature






Sintering
dielectric

characteristic
Resonant



Sample
temperature
constant
fQ
τf
frequency



No.
(° C.)
εr
(GHz)
(ppm/° C.)
f0 (GHz)
Remarks







80
850
8.5
17500
−38
14.0
Invention Example



81
850
10.3
16500
−35
12.5
Invention Example



82
850
10.2
16500
−36
12.5
Invention Example



83
1000
11.5
17000
−30
10.5
Invention Example



84
1150
10.8
7400
−35
12.2
Comparative Example



85
1000
11.0
15000
−33
11.8
Invention Example



86
1000
11.2
16000
−38
11.2
Invention Example



87
1000
11.1
15800
−35
11.8
Invention Example



88
980
12.1
15000
−30
9.7
Invention Example



89
950
11.8
16500
−40
11.5
Invention Example



90
950
10.5
15500
−41
12.0
Invention Example



91
900
10.3
15000
−38
11.5
Invention Example



92
1000
10.4
15500
−40
10.3
Invention Example







Asterisks indicate that the marked features are outside the scope of the present invention.






The results shown in Table 1 to 5 show that nearly all of the invention examples exhibited an fQ value of 15,000 GHz or more, a low dielectric loss in the high-frequency band, and a resonant frequency temperature coefficient τf of within ±50° C./ppm. This is presumably due to the effect of incorporating Ln2O3 into the glass composition together with the filler. At a small Ln2O3 content, the fQ value is low, as shown by Samples 1 in Table 1 and Sample 29 in Table 2.
The invention examples produced sufficiently dense sinters having high fQ values even at a sintering temperature of 1,000° C. or less. This is because the contents of the Ln2O3, RO, Al2O3, and TiO2 are limited within particular ranges. This fact is clearly supported by the results of Samples 7, 8, 9, 23, 24, 28, 36, 41, 47, 74, and 84 compositions which were outside the ranges of the invention, since they did not achieve the target fQ value or they required high sintering temperatures.
RO has an effect of decreasing the sintering temperature. However, at an excessively large RO content, the temperature coefficient τf of the resonant frequency tends to be excessively shifted toward the negative side, as shown by Samples 13, 44, and 47.
Incorporation of WO3 or M2O decreases the sintering temperature, and WO3 or M2O can be effectively used by controlling its content. At an excessively large content, however, a significant decrease in fQ value or degradation of temperature coefficient τf may result, as shown by Samples 18, 19, 54, 59, 68, and 71.
INDUSTRIAL APPLICABILITY
A ceramic composition of the present invention has a low dielectric loss in the high-frequency band and low temperature dependence of the resonant frequency. Moreover, since its characteristics can be exhibited at a low sintering temperature, a metal, such as Ag or Cu, having a low specific resistance can be used as the material for the metal wiring or electrode, and the conductor loss can thus be decreased. The ceramic composition of the present invention is thus suitable for the substrate materials for high-frequency band multilayer substrates and the materials for electronic components.

## Claims

1. A ceramic composition comprising a glass composition and 0.1 to 0.4 mol of a filler which is at least one of Al2O3 and TiO2, wherein the composition of the glass composition comprises 0.15 to 0.55 mol of a which is an oxide or oxide precursor of a rare earth element or mixtures thereof, 0.45 to 0.85 mol of b which is boron oxide B2O3 or an oxide precursor thereof, wherein a+b=1 mol, and 0.01 to 0.2 mol of an oxide or oxide precursor of an alkaline earth metal element.

2. The ceramic composition according to claim 1, comprising a positive amount of up to 0.05 mol of tungsten oxide or an oxide precursor thereof.

3. The ceramic composition according to claim 2 in which the amount of tungsten oxide or precursor is at least 0.005 mol.

4. The ceramic composition according to claim 3, comprising 0.0005 to 0.002 mol of an oxide or oxide precursor of an alkali metal element M.

5. The ceramic composition according to claim 2, comprising 0.0005 to 0.002 mol of an oxide or oxide precursor of an alkali metal element M.

6. The ceramic composition according to claim 1 which contains 0.0005 to 0.002 mol of an oxide or oxide precursor of an alkali metal.

7. The ceramic composition according to claim 1 in which the rare earth element is at least one of La and Nd.

8. The ceramic composition according to claim 1 in which the alkaline earth metal comprises Ca.

9. The ceramic composition according to claim 1 in which the filler comprises Al2O3.

10. The ceramic composition according to claim 1 in which the filler comprises TiO2.

11. The ceramic composition according to claim 1 in which each of the oxides or precursors is the oxide.

12. The ceramic composition according to claim 11, comprising a positive amount of up to 0.05 mol of tungsten oxide.

13. The ceramic composition according to claim 12, comprising 0.0005 to 0.002 mol of an oxide of an alkali metal element, and in which the rare earth element is at least one of La and Nd, and the alkaline earth metal comprises Ca.

14. The ceramic composition according to claim 13 in which the filler comprises Al2O3.

15. The ceramic composition according to claim 14, in which the tungsten oxide amount is 0.005 to 0.05 mol.

16. The ceramic composition according to claim 13 in which the filler comprises TiO2.

17. A compact comprising a sintered composition of claim 16.

18. A compact comprising a sintered composition of claim 14.

19. A compact comprising a sintered composition of claim 10.

20. A compact comprising a sintered composition of claim 9.

21. A compact comprising a sintered composition of claim 1.