JPH0773735A - Dielectric porcelain composition for high frequency - Google Patents

Abstract

PURPOSE:To provide a dielectric porcelain composition provided with a high dielectric constant and a high Q value in a high frequency area. CONSTITUTION:A dielectric porcelain composition consists of complex oxide containing at least Ba, Zn, W as metal elements, and its composition formula by mole rate of these metal elements is represented as aBaO.bZnO.cWO3. In this formula, (a), (b), (c) satisfy the following relations such as 0.40<=(a)<=0.55, 0.15<=(b)<=0.39, 0.20<=(c)<=0.30, (a)+(b)+(c)=1.00.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel dielectric ceramic composition having a high dielectric constant and a high Q value in a high frequency region such as microwave and millimeter wave.

[0002]

2. Description of the Related Art Dielectric ceramics are widely used for dielectric resonators, dielectric substrates for MICs, etc. in a high frequency range such as microwaves and millimeter waves.

Conventionally, as a dielectric ceramic of this type,
For example, a MgTiO ₃ —CaTiO ₃ based material is known. Such a material has a dielectric constant of about 20 and 1 GHz.
It has a characteristic that the Q value converted into is about 20,000.

[0004]

However, in recent years, the frequency of use has become higher due to the diversification of equipment used, and dielectric characteristics, particularly high Q value, in such a high frequency region have been required. However, the conventional dielectric material as described above has not yet achieved a high Q value of a practical level. Further, there is a problem that the relative dielectric constant is still low.

Therefore, an object of the present invention is to provide a novel dielectric ceramic composition having a high Q value and a high relative dielectric constant in the high frequency region.

[0006]

Means for Solving the Problems As a result of studying the above problems, the present inventors have found that Ba as a metal element,
The present inventors have found that excellent dielectric properties can be obtained by setting a complex oxide containing Zn and W to a predetermined ratio, and have reached the present invention.

That is, the dielectric ceramic composition of the present invention is a composite oxide containing at least Ba, Zn, and W as metal elements, and the composition formula based on the molar ratio of these metal elements is aBaO.bZnO.cWO. _When expressed as ₃ , the a,
b and c are 0.40 ≦ a ≦ 0.55, 0.15 ≦ b ≦
0.39, 0.20 ≦ c ≦ 0.30, a + b + c = 1.
The composition satisfies 00.

In the dielectric ceramic composition of the present invention, Ba
The molar ratio of O is set to 0.40 ≦ a ≦ 0.55 because
When a is smaller than 0.40, the Q value decreases, and 0.
If it is larger than 55, sintering tends to be difficult. Particularly, it is preferable that 0.43 ≦ a ≦ 0.53.

Further, the molar ratio of ZnO is 0.15 ≦ b ≦
The reason for setting 0.39 is that if b is less than 0.15, the sintering becomes difficult or the Q value decreases, and if it exceeds 0.39, the Q value decreases. is there. In particular, it is preferable that 0.20 ≦ b ≦ 0.35.

The molar ratio of WO ₃ is 0.20≤c≤0.30.
The reason for this is that if c is less than 0.20, the sinterability is reduced, and if it is greater than 0.30, the Q value is reduced, resulting in poor sintering. Especially 0.22 ≦
It is preferable that c ≦ 0.28.

The dielectric material of the present invention is made of Ba, Z
It is a complex oxide containing n and W, and is mainly Ba (Zn
_1/2 W _1/2) 0 ₃ perovskite crystal phase represented the one in which a main crystal phase, but also include those other than the perovskite-type crystal phase as long as the composition satisfies the above range good. The material having such a crystal may itself be a polycrystal such as a sintered body or a single crystal.

The composition range of the present invention is shown in the ternary diagram of FIG. In FIG. 1, the region surrounded by points abcdaa is the composition range of the present invention.

As a method for producing a porcelain according to the present invention, for example, an oxide of Ba, Zn, W or a metal salt such as a carbonate or a nitrate which produces an oxide by firing is used as a raw material, and these are in the above-mentioned range. It is weighed so as to be, then wet-milled with a ball mill, dehydrated and dried. After this,
The mixture is calcined at 500 to 1500 ° C. for 0.1 to 100 hours, put in a ball mill, mixed and pulverized with a solvent and an organic binder, and granulated or sized.
Then, the calcined powder is press-molded at a predetermined pressure to be molded into a predetermined shape, for example, and then in the atmosphere,
By firing at 1750 ° C. for 0.1 to 200 hours, a dielectric ceramic with a relative density of 90% or more can be obtained.

[0014]

The present invention will be described in the following examples.

BaCO _{3 having} a purity of 99% or more as a raw material,
ZnO and WO ₃ powders were used and weighed in the proportions shown in Table 1, put together with water in a ball mill lined with rubber, and wet-mixed using ZrO ₂ balls having a diameter of 10 mm. Next, this mixture was dehydrated and dried, and then calcined at 1200 ° C. for 2 hours, and the calcined product was wet-ground by adding water and an organic binder to a ball mill.

Thereafter, the pulverized product was dried and then granulated through a mesh of No. 50 mesh to obtain 1 ton of the obtained powder.
A disk having a size of 20 mmφ × 10 mm was formed at a pressure of / cm ² . Furthermore, this disk is 1400 to 1500
A porcelain sample was obtained by firing under the condition of ° C x 2 hours. This porcelain sample was processed to obtain a cylinder having dimensions of 14 mmφ × 7 mm.

With respect to the thus obtained porcelain sample, the relative permittivity (εr) and Q value at a frequency of 5 to 7 GHz were measured by the dielectric resonator method, and the resonance frequency in the temperature range from 25 ° C to 85 ° C was measured. The temperature change was measured and the temperature coefficient (τf) of the resonance frequency was calculated. The Q value was converted into the Q value at 1 GHz from the relationship of Q value generally established in the microwave dielectric × measurement frequency f = constant. The results are shown in Table 1.

[0018]

[Table 1]

According to Table 1, the sample No. having a composition deviated from the scope of the present invention. Nos. 4 to 9 and 18 had a Q value of 1000 or less, or caused defective sintering. On the other hand, the samples of the present invention achieved a relative dielectric constant of 22 to 28 and a Q value of 23,000 or more.

Further, the X-ray diffraction measurement was performed on the porcelain of Sample No. 10, and the results are shown in FIG. According to FIG. 2, it can be understood from the peak marked with a circle that it is a perovskite type crystal structure, and its composition formula is Ba (Zn _1/2 W _1/2 ).
It is estimated to be 0 ₃ .

[0021]

As described in detail above, according to the present invention, a composite oxide containing at least Ba, Zn, and W as metal elements, and the composition formula based on the molar ratio of these metal elements is aBaO.bZnO.・ When expressed as cWO ₃ , a,
By setting b and c to predetermined values, a high dielectric constant and a high Q value can be obtained in a high frequency region. As a result, it can be sufficiently applied to resonator materials used in the microwave and millimeter wave regions, dielectric substrate materials for MIC, and other electronic parts.

[Brief description of drawings]

FIG. 1 is a ternary diagram of BaO—ZnO—WO ₃ showing the scope of the present invention.

FIG. 2 is an X-ray diffraction chart of Sample No. 10 in the examples.

Claims (1)

[Claims] 1. At least Ba, Zn and W as metal elements.
A composite oxide containing, when the composition formula by molar ratio of the metal elements expressed as aBaO · bZnO · cWO _3, wherein a, b, c is 0.40 ≦ a ≦ 0.55 0. 15 ≦ b ≦ 0.39 0.20 ≦ c ≦ 0.30 a + b + c = 1.00 is satisfied, The high frequency dielectric ceramic composition.