JP2001302334A - Dielectric ceramic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric ceramic composition having high dielectric constant, large Q-value and excellently stable τf. SOLUTION: The dielectric ceramic composition consists of calcium, titanium, aluminum, tantalum and oxygen and is expressed by a composition formula, aCaTiO3-(1-a)Ca(Al1/2Ta1/2)O3 (in the formula, 0.25<=a<=0.6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dielectric ceramic composition comprising calcium, titanium, aluminum, tantalum and oxygen suitable as a dielectric resonator material. The dielectric ceramic composition of the present invention can be used for, for example, a microwave IC substrate, a dielectric adjustment rod, and the like, in addition to the dielectric resonator material.

[0002]

2. Description of the Related Art In recent years, with the integration of microwave circuits,
There is a need for a small, high-performance dielectric resonator. The dielectric porcelain composition used for such a dielectric resonator includes:
Characteristics such as a large relative dielectric constant εr, excellent stability in the temperature coefficient τf of the resonance frequency, excellent linearity in the temperature characteristics of the resonance frequency, and a large unloaded Q are required.

[0003]

Conventionally, as such a dielectric ceramic composition, a composition mainly composed of TiO ₂ , BaO—TiO _2, etc. has been known. Has a large dielectric loss and is difficult to put to practical use.

Further, Ba (Mg _1/3 Ta _2/3 ) O ₃ type, B
a (Zn _1/3 Ta _2/3 ) O ₃ type, Ba (Zn _1/3 Nb _2/3 )
Dielectric ceramic compositions having a perovskite structure such as an O ₃ -based structure are also known. However, since these have low dielectric constants, there is a drawback that the resonator becomes too large in, for example, the 0.1 to 5 GHz band.

An object of the present invention is to provide a dielectric ceramic composition suitable as a dielectric resonator material, particularly a dielectric resonator material used in the 0.1 to 5 GHz band. Another object of the present invention is to provide a high dielectric constant, a large Q value,
An object of the present invention is to provide a dielectric ceramic composition having good stability.

[0006]

Means for Solving the Problems The present inventors have found that among a number of component elements used in a dielectric porcelain composition, a specific porcelain composition comprising a combination of calcium, titanium, aluminum, tantalum and oxygen. It has been found that the object can be achieved by a product. In the present invention, the composition formula aC
_{aTiO 3 - (1-a)} Ca (Al 1/2 Ta 1/2) O 3 ( wherein, 0.25 ≦ a ≦ 0.6) represented by, becomes calcium, titanium, aluminum, tantalum and oxygen The present invention relates to a dielectric porcelain composition. In the present invention, CaTiO ₃ and Ca (Al _1/2 Ta)
_1/2 ) The above-mentioned dielectric ceramic composition having a composite perovskite structure with O ₃ is preferred.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The dielectric ceramic composition of the present invention has a large relative dielectric constant, so that the size of the resonator can be reduced and the no-load Q can be increased. Further, the temperature coefficient τf of the resonance frequency is small.

The dielectric porcelain composition of the present invention is a composite oxide containing Ca, Ti, Al, and Ta as metal elements. The reasons for limiting these compositions to the above range are as follows.

The reason for setting 0.25 ≦ a ≦ 0.6 is that if a is excessively large, τf becomes positive and exceeds 50 ppm / ° C. If a is excessively small, the dielectric constant decreases, and τf becomes large negatively and exceeds -70 ppm / ° C.

An example of a preferred method for producing the dielectric ceramic composition of the present invention will be described below. Calcium carbonate, titanium oxide,
A predetermined amount of the starting material of aluminum oxide and tantalum oxide is wet-mixed with a solvent such as water or alcohol. Subsequently, after removing water, alcohol, and the like, pulverization is performed, and 1000 to 130 under an oxygen-containing gas atmosphere (for example, an air atmosphere).
Calcinate at 0 ° C for about 2 to 10 hours. The calcined product formed by this is pulverized, mixed with an organic binder such as polyvinyl alcohol to homogenize, dried and pulverized,
Press molding (pressure 100 to 1000 kg / cm ² ).
Then, when this molded product is fired at 1350 to 1650 ° C. in an oxygen-containing gas atmosphere such as air, the dielectric ceramic composition represented by the above composition formula is obtained.

The dielectric ceramic composition thus obtained can be processed as it is or as necessary into an appropriate shape and size to obtain a dielectric resonator, a dielectric substrate for microwave IC, a dielectric adjusting rod. And the like. Particularly, when a dielectric resonator used in the 0.1 to 5 GHz band is used, an excellent effect is obtained.

The raw materials of calcium, titanium, aluminum and tantalum are CaCO ₃ , TiO ₂ , A
In addition to l ₂ O ₃ , Ta ₂ O _5, etc., carbonates, hydroxides and the like which become oxides during firing can be used.

[0013]

The present invention will be described more specifically with reference to the following examples. Example 1 [Sample No. 1] calcium carbonate (CaCO ₃ ) powder,
Titanium oxide (TiO ₂ ) powder, aluminum oxide (Al ₂
O ₃ ) powder and tantalum oxide (Ta ₂ O ₅ ) powder were put into a ball mill together with ethanol, and wet-mixed for 12 hours.
Ethanol as a solvent was removed from the mixture, and the mixture was pulverized for 1 hour with a triturator to obtain 0.6CaTiO ₃ -0.4Ca (A
A calcined powder of l _1/2 Ta _1/2 ) O ₃ was obtained.

Next, an appropriate amount of a polyvinyl alcohol solution was added to the calcined powder, and the mixture was uniformly mixed.
φ, 4mmt thick pellets molded under air atmosphere 1
It was fired and sintered at 500 ° C. for 2 hours to obtain a dielectric ceramic composition of the present invention. After the thus obtained porcelain composition was cut into an appropriate size, it was measured by the dielectric resonance method, and the unloaded Q and the relative permittivity εr at the resonance frequency f ₀ (4 to 6 GHz) were obtained. The temperature dependence of the resonance frequency was measured in the range of -40 to 80 ° C, and the temperature coefficient τ
f was determined. Table 1 shows the results.

[Sample No. 2-No. 13] Sample N
o. Sample No. 1 was changed except that the mixing ratio of calcium carbonate, titanium oxide, aluminum oxide, and tantalum oxide was changed as shown in Table 1. A dielectric ceramic composition was manufactured in the same manner as in Example 1, and the characteristics were measured in the same manner. Table 1 shows the results.
Those marked with * in the table are comparative examples outside the scope of the present invention. Also, in Table 1 No. X-ray diffraction of the dielectric porcelain composition obtained in 5
It was found that the composite material had a composite perovskite structure of iO ₃ -0.5Ca (Al _1/2 Ta _1/2 ) O ₃ . FIG. 1 shows the X-ray diffraction diagram.

As is clear from Table 1, the dielectric obtained by the present invention has a relative dielectric constant of 35 or more and an f ₀ × Q value of 300.
At least 00, excellent dielectric properties with a τf of −70 to +50 ppm / ° C. or less were obtained. On the other hand, for dielectrics outside the scope of the present invention, 12, the dielectric constant is as large as 64.8, but τf is as large as 119 ppm / ° C. Also, N
o. 13, the dielectric constant is reduced to 25.9, and τf
Also becomes negatively large at −78 ppm / ° C.

[0017]

According to the present invention, a dielectric ceramic composition having a high dielectric constant, a large Q value, and a good stability of τf can be obtained.

[0018]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a graph showing X of the dielectric ceramic composition obtained by the present invention.
FIG.

Continued on the front page F term (reference) 4G030 AA08 AA16 AA21 AA36 BA09 CA01 5E001 AE00 AE03 5G303 AA02 AA05 AA10 AB06 AB08 AB11 BA12 CA01 CB01 CB06 CB33 CB35 5J006 HC07 LA02 LA12

Claims (2)

[Claims] 1. Composition formula aCaTiO _3- (1-a) C
a (Al _1/2 Ta _1/2 ) O ₃ (where, 0.25 ≦ a ≦ 0.
6. A dielectric ceramic composition represented by 6), comprising calcium, titanium, aluminum, tantalum and oxygen. 2. CaTiO ₃ and Ca (Al _1/2 Ta _1/2 )
The dielectric ceramic composition of claim 1, wherein it is a complex perovskite structure of O _3.