JP3318396B2 - High frequency dielectric ceramic composition - Google Patents

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 range such as microwaves and millimeter waves.

[0002]

2. Description of the Related Art In the high frequency region such as microwaves and millimeter waves, dielectric ceramics are widely used for dielectric resonators, MIC dielectric substrates, and the like.

[0003] Conventionally, as this kind of dielectric porcelain,
For example, MgTiO ₃ -CaTiO ₃ based materials are known. Such a material has a dielectric constant of about 20 and 1 GHz.
It has a characteristic that the Q value converted to 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 properties, especially high Q value, in such a high frequency region have been required. However, the conventional dielectric materials as described above have not yet achieved a practically high Q value. There is also a problem that the relative dielectric constant is still low.

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

[0006]

Means for Solving the Problems The present inventors have studied the above problems, and as a result, as a metal element, Ba,
The inventors have found that when the composite oxide containing Zn and W is set at a predetermined ratio, excellent dielectric properties can be obtained, and have reached the present invention.

That is, the dielectric ceramic composition of the present invention mainly comprises a composite oxide composed of Ba, Zn, and W as metal elements.
Be one that, when expressed as aBaO · bZnO · cWO ₃ the composition formula by molar ratio of the composite oxide, 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.
It is a composition that satisfies 00.

[0008] In the dielectric ceramic composition of the present invention, Ba
The molar ratio of O was set to 0.40 ≦ a ≦ 0.55 because
If a is smaller than 0.40, the Q value decreases, and
If it is larger than 55, sintering tends to be difficult. In particular, 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, sintering becomes difficult or the Q value decreases, and if b is more than 0.39, the Q value decreases. is there. In particular, it is preferable that 0.20 ≦ b ≦ 0.35.

When the molar ratio of WO ₃ is 0.20 ≦ c ≦ 0.30
The reason is that when c is less than 0.20, the sinterability decreases, and when c is more than 0.30, the Q value decreases, resulting in poor sintering. Especially 0.22 ≦
It is preferable that c ≦ 0.28.

Further, the dielectric material of the present invention comprises Ba, Z
mainly composed of a composite oxide consisting of n and W, and mainly B
The main crystal phase is a perovskite crystal phase represented by a (Zn _1/2 W _1/2 ) ₃ , but other than the perovskite crystal phase as long as the composition satisfies the above range. May be included. The material having such a crystal may be in any form of 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, a region surrounded by a point abcda is the composition range of the present invention.

According to the method for producing porcelain based on the present invention, for example, oxides of Ba, Zn, and W or metal salts such as carbonates and nitrates that form oxides upon firing are used as raw materials, After being weighed so as to obtain, the mixture is wet-pulverized with a ball mill and dehydrated and dried. After this,
The mixture is calcined at 500 to 1500 ° C for 0.1 to 100 hours, and the calcined product is put into 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 form a predetermined shape, for example, in the air at 1200 to 1200 m.
By firing at 1750 ° C. for 0.1 to 200 hours, a dielectric ceramic having a relative density of 90% or more can be obtained.

[0014]

The present invention will be described below with reference to the following examples.

BaCO _{3 having} a purity of 99% or more as a raw material;
Using ZnO and WO ₃ powders, they were weighed in the proportions shown in Table 1 and put into a ball mill lined with rubber together with water, and wet-mixed using ZrO ₂ balls having a diameter of 10 mm. Next, after dehydrating and drying this mixture, it was calcined at 1200 ° C. for 2 hours, and the calcined product was wet-pulverized by putting water and an organic binder into a ball mill.

Thereafter, the pulverized material was dried, and then granulated through a No. 50 mesh net.
/ Cm ^{2 at} a pressure of 20 cmφ × 10 mm. Furthermore, this disk is
A porcelain sample was obtained by firing under the conditions of ° C. × 2 hours. This porcelain sample was processed to obtain a cylinder having a size of 14 mmφ × 7 mm.

With respect to the porcelain sample thus obtained, the relative dielectric constant (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. The temperature change was measured, and the temperature coefficient (τf) of the resonance frequency was calculated. The Q value was converted to a Q value at 1 GHz based on a fixed relation between the Q value generally established in the microwave dielectric and the measurement frequency f = constant. The results are shown in Table 1.

[0018]

[Table 1]

According to Table 1, Sample No. whose composition is out of the range of the present invention. In Nos. 4 to 9 and 18, the Q value was 1000 or less or poor sintering occurred. In contrast, the sample of the present invention achieved a relative dielectric constant of 22 to 28 and a Q value of 23,000 or more.

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 is understood from the peaks indicated by the circles that the crystal structure is a perovskite crystal structure, and the composition formula thereof is Ba (Zn _1/2 W _1/2 ).
It is estimated to be 0 ₃ .

[0021]

As described above in detail, according to the present invention, a composite oxide composed of Ba, Zn and W is mainly used as a metal element.
Been made to a, when representing the formula by molar ratio of the composite oxide and _{aBaO · bZnO · 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. Thereby, it can be sufficiently applied to resonator materials, MIC dielectric substrate materials, and other electronic components used in the microwave or millimeter wave region.

[Brief description of the 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 Examples.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01B 3/12 314 C04B 35/495 H01P 7/10

Claims (1)

(57) [Claims] 1. A composition mainly comprising a composite oxide composed of Ba, Zn, and W as a metal element, wherein a composition formula based on a mole ratio of the composite oxide is aBaO.multidot. When expressed as bZnO · cWO ₃ , the a, b, and c satisfy 0.40 ≦ a ≦ 0.55 0.15 ≦ b ≦ 0.39 0.20 ≦ c ≦ 0.30 a + b + c = 1.00 A dielectric ceramic composition for high-frequency waves, comprising: