JPH08119736A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE: To obtain a dielectric ceramic composition which can be produced at 900 deg.C or lower firing temperature and can be used in the high-frequency range. CONSTITUTION: (A) The main components of 46-62mole% of TiO2 , 30-44 mole % of ZrO2 , 0.5-11.5 mole % of CeO2 , 0.5-11.5wt.% of LaO3/2 and 0.5-11.5 mole % of SnO2 are combined with (B) as the first sub-components, at least one selected from among Cr2 O3 , Al2 O3 and SiO2 in the total amount of 0.01-1.0wt.% based on the main components to prepare 25-60wt.% of the ceramic composition. Further, this ceramic composition is mixed with (C) the second sub-components, 10-40wt.% of SiO2 , 1-20wt.% of at least one selected from among CaO, SrO and BaO, 1-15wt.% of MgO, 3-30wt.% of B2 O3 and 0.1-3.0wt.% of LiO2 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition for use in high frequency laminated ceramic capacitors, dielectric resonators and the like.

[0002]

2. Description of the Related Art Conventionally, TiO ₂ , ZrO ₂ and CeO have been used as dielectric ceramic materials that can be used in a high frequency range.
A dielectric ceramic composition containing ₂ , LaO _3/2, and SnO ₂ as main components is known (Japanese Patent Laid-Open No. 3-246810).

[0003]

THE INVENTION Problems to be Solved] However, the conventional _{TiO 2 -ZrO 2 -CeO 2 -LaO 3/2} -SnO 2
Since the firing temperature of the porcelain composition is relatively high at 1200 to 1400 ° C., a conductive paste containing palladium (Pd) having a high melting point as a main component must be used as an internal electrode material when manufacturing a laminated porcelain capacitor. There wasn't. However, Pd has the drawback that the Q value of the capacitor is lowered due to its high resistivity and that it is expensive. Therefore, an object of the present invention is to provide a dielectric ceramic composition which can be manufactured at a firing temperature of 900 ° C. or lower and can be used in a high frequency range.

[0004]

In order to achieve the above object, the dielectric ceramic composition of the present invention is TiO ₂ 46-62 m.
ol%, ZrO ₂ 30 to 44 mol%, CeO ₂ 0.5
~ 11.0 mol%, LaO3 _{/ 2} 0.5-11.0mo
1% and SnO ₂ 0.5 to 11.0 mol%, with respect to the main component, at least one component selected from Cr ₂ O ₃ , Al ₂ O ₃ and SiO ₂ is used as the main subcomponent. 25 to 60% by weight of the porcelain composition component added in a total amount of 0.01 to 1.0% by weight with respect to the components, and as a second accessory component,
SiO ₂ 10-40% by weight, CaO, SrO and Ba
1 to 20% by weight of at least one component selected from O
And MgO 1 to 15% by weight, B ₂ O ₃ 3 to 30% by weight, and Li ₂ O 0.1 to 3.0% by weight.

[0005]

The dielectric ceramic composition of the present invention has a relative permittivity ε _r of 8 or more, a Q value of 1400 or more, and a temperature coefficient τ ε of the relative permittivity of −60 ppm / ° C. to +60 ppm / at 1 MHz.
It is in the range of ° C, and the firing temperature can be lowered.

[0006]

EXAMPLES The present invention will be described in detail below based on examples and comparative examples. In order to obtain dielectric porcelain for high frequency porcelain capacitors, samples of 62 types of compositions shown in Tables 1 and 2 were prepared. In Tables 1 and 2, the content of each component after firing is shown in wt%. However, TiO ₂ , Z as the main component
The composition of rO ₂ , CeO ₂ , LaO _3/2 and SnO ₂ is m.
ol%, Cr ₂ O ₃ , Al ₂ O ₃ as the first subcomponent
And SiO ₂ are shown by weight% based on the total of the main components. For the second subcomponent, SiO ₂ , CaO, Sr
The content of O, BaO, MgO, B ₂ O ₃ and Li ₂ O in the porcelain after firing was shown by weight%.

[0007]

[Table 1]

[0008]

[Table 2]

Next, the sample No. Based on 1,
The method for producing the raw material powder and the method for producing the high frequency porcelain capacitor will be described in detail below. First, TiO ₂ and ZrO
₂ , CeO ₂ , LaO _3/2 , SnO ₂ and Al ₂ O ₃ were mixed at a predetermined ratio as shown in Table 1, put in a polyethylene pot together with water, wet mixed, and then dehydrated and dried. The dried product was calcined in the air at 1200 ° C. for 2 hours to obtain a component material of the porcelain composition.

Next, in the porcelain after firing, SiO ₂ 20
% By weight, SrO 10% by weight, MgO 10% by weight, B
To allowed to contain a second subcomponent at a rate of ₂ O ₃ 9% by weight and Li ₂ O 1% by weight, SiO ₂ 40 wt%, Sr
SiO ₂ , SrCO ₃ , MgO, B ₂ O ₃ and Li so as to obtain a second subcomponent having a composition of 20 wt% O, 20 wt% MgO, 18 wt% B ₂ O ₃ and 2 wt% Li ₂ O. ₂ CO ₃ was weighed, and these raw materials were put into a polyethylene pot together with water, wet mixed, and then dehydrated and dried.
The dried product was calcined in air at 850 ° C. for 2 hours to obtain a second subcomponent material.

Next, each material was weighed in a ratio of 50% by weight of the above-mentioned porcelain composition component material and 50% by weight of the second subcomponent material, and this was put in a polyethylene pot together with water, wet-mixed and then dehydrated and dried. Then, porcelain raw material powder was obtained. next,
An organic binder was added to this porcelain raw material powder for granulation, and the granulated product was pressure-molded into a disk shape having a diameter of 9.8 mm and a thickness of 0.6 mm at a pressure of 500 kg / cm ² . next,
Place this molded body on a zirconia setter and put it in air 900
It was fired at a temperature of ° C. Silver paste was applied to both main surfaces of the disc-shaped porcelain obtained by the main firing and baked to obtain a porcelain capacitor composed of the porcelain 1 and a pair of electrodes 2 and 3 shown in FIG.

Next, the relative permittivity ε _r , Q value, and temperature coefficient τ ε (ppm / ° C.) of the relative permittivity of this ceramic capacitor were measured. Note that the relative permittivity ε _r and Q value are frequency 1 MHz.
_It was measured under the conditions of _{Z 2} , voltage 1 V and ambient temperature 20 ° C. The temperature coefficient τε is +2 based on the relative permittivity ε _r of + 20 ° C.
Change rate of relative permittivity ε _{r from} 0 to + 85 ° C, 1 MH
_Z was measured under the condition of 1V. Sample No. Sample Nos. 2 to 62, except that the composition of the main component and / or the first and second subcomponents was changed. A porcelain capacitor was made by the same method as in No. 1 and the characteristics were measured by the same method. However, CaO and BaO of the second subcomponent are
CO ₃ and BaCO ₃ were used. Sample No. The characteristics of 1 to 62 are as shown in Table 3. It should be noted that the samples with * in Tables 1 to 3 are outside the scope of the present invention.

[0013]

[Table 3]

As is clear from Table 3, according to the porcelain composition in the composition range specified in the present invention, the relative permittivity ε _r is 8
.About.12.5, Q is 1400 to 2000, and temperature coefficient .tau..epsilon. Of relative permittivity is -60 to +60 (ppm / .degree. C.). The reasons for limiting the composition range will be described below based on the results shown in Table 3. Regarding the main component, Ti
When O ₂ is less than 46 mol%, the relative permittivity ε _r is low, Q is small, and τ ε becomes too large (Sample No. 22). When TiO ₂ exceeds 62 mol%, τ
ε becomes too large negatively (Sample No. 27).
Further, when ZrO ₂ is less than 30 mol%, τε becomes too large negatively (Sample No. 28), and ZrO ₂
Is more than 44 mol%, Q is small and τε is too large (Sample No. 23). In addition, CeO
_{When 2} is less than 0.5 mol%, Q is small (sample N
o. 25, 26) and when CeO ₂ exceeds 11.0 mol%, the Q is small (Sample No. 24). Also, LaO
_{When 3/2} is less than 0.5 mol%, Q is small (Sample Nos. 24 and 26), and when LaO _3/2 exceeds 11.0 mol%, Q is small (Sample No. 25). Also, Sn
When O ₂ is less than 0.5 mol%, Q is small (Sample Nos. 24 and 25), and when SnO ₂ exceeds 11.0 mol%, Q is small (Sample No. 26).

Regarding the first subcomponent, Cr ₂ O ₃ and Al ₂
If the sum of O ₃ and SiO ₂ is less than 0.01% by weight,
Small Q (Sample Nos. 33, 34, 35), Cr ₂ O ₃
If the sum of Al ₂ O ₃ and SiO ₂ exceeds 1% by weight, the relative permittivity ε _r is low and τ ε becomes too large (Sample Nos. 36, 37, 38).

Regarding the second subcomponent, when SiO ₂ is less than 10% by weight, Q is small (Sample No. 49) and S is S.
If iO ₂ exceeds 40% by weight, sintering does not occur at 900 ° C. (Sample No. 50). Also, CaO, SrO and Ba
If the sum of O is less than 1% by weight, sintering does not occur at 900 ° C. (Sample No. 51), and if the sum of CaO, SrO and BaO exceeds 20% by weight, the relative permittivity ε _r is low, and Q Is small (Sample No. 52). Further, when MgO is less than 1% by weight, it does not sinter at 900 ° C. (Sample No. 53) and M
When gO exceeds 15% by weight, the relative permittivity ε _r is low and Q
Is small (Sample No. 54). Also, B ₂ O ₃ is 3% by weight
If it is less than 900 ° C., sintering does not occur at 900 ° C. (Sample No. 5
5), if B ₂ O ₃ exceeds 30% by weight, sintering does not occur at 900 ° C. (Sample No. 56). Also, Li ₂ O is 0.1
If it is less than wt%, it will not sinter at 900 ° C (Sample N
o. 57), if Li ₂ O exceeds 3.0% by weight, 90
It does not sinter at 0 ° C. (Sample No. 58).

Further, regarding the above-mentioned porcelain composition component material, when the content rate is less than 25% by weight, the relative permittivity ε _r is low, the Q is small (Sample No. 61), and the content rate is 60% by weight. When it exceeds, it does not sinter at 900 ° C. (Sample No.
62). Sample No. 1 to 62, a single-layer porcelain capacitor was manufactured and measured in order to easily compare the characteristics of the dielectric porcelain. Instead, as shown in FIG. An internal electrode 12 made of a low melting point metal such as Ag), Ag-Pd, or copper (Cu) is provided.
A similar effect was obtained when a porcelain capacitor having a pair of external electrodes 13 and 14 connected thereto was manufactured and subjected to the same measurement. When manufacturing such a laminated porcelain capacitor, a porcelain raw sheet (green sheet) coated with a conductive paste for internal electrodes is laminated to form a raw chip, and the internal electrodes are baked and the porcelain is fired at the same time. However, since the porcelain 11 according to the present invention can be obtained by firing at 900 ° C. or lower, the above-mentioned Ag and Ag having a small resistivity as the internal electrode 12 are obtained.
It becomes possible to use a low melting point metal such as -Pd or Cu, and an improvement in Q value is achieved.

The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible. (1) CaCO as a starting material for obtaining the second subcomponent
Instead of ₃ , SrCO ₃ , BaCO ₃ and LiCO ₃ , CaO, SrO, BaO and Li ₂ O can be used. (2) The main firing temperature is, for example, 7 instead of 900 ° C.
It can be changed within a range of about 50 to 1200 ° C. (3) The dielectric porcelain composition of the present invention can also be used for porcelain of dielectric resonators, multilayer circuit boards, and the like.

[0019]

As described in detail above, the dielectric ceramic composition of the present invention can be obtained by co-firing with a conductive paste layer of a low melting point metal such as Ag, Ag-Pd, or Cu. It is suitable as a dielectric porcelain of a high frequency laminated ceramic capacitor. The Q value can be increased by forming the internal electrodes of the laminated porcelain capacitor with a metal having a low resistivity such as Ag, Ag-Pd, or Cu.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a single-layer ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a laminated ceramic capacitor according to an example of the present invention.

[Explanation of symbols]

 1 porcelain 2, 3 electrode 11 porcelain 12 internal electrode 13, 14 external electrode

Claims (1)

[Claims] 1. TiO ₂ 46 to 62 mol%, ZrO ₂
30-44 mol%, CeO ₂ 0.5-11.0 mo
1%, LaO _3/2 0.5-11.0 mol% and SnO
To a principal component composed of _{2 0.5~11.0mol%,} as an auxiliary component, at least one component selected from _{Cr 2 O 3, Al 2 O} 3 and SiO ₂ in a total amount with respect to the main component 0.01 to 1.0 wt% added component 25 to 60 wt%
SiO ₂ 10 to 40% by weight, at least one component selected from CaO, SrO, and BaO 1 to 20% by weight, MgO 1 to 15% by weight, B ₂ O ₃ 3 to 30% by weight, A dielectric ceramic composition comprising 0.1 to 3.0% by weight of Li ₂ O.