JP2887244B2 - 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 high frequency dielectric ceramic composition having a high dielectric constant and a high Q value in a high frequency region 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, ZrO ₂ —SnO ₂ —TiO ₂ based material, BaO—
TiO ₂ materials, (Ba, Sr) (Zr, Ti) O ₃ based materials, Ba (Zn, Ta) O ₃ based materials and the like are known.

[0004] The above materials have a frequency of 50 due to various improvements.
At 0 MHz to 5 GHz, the dielectric constant is 20 to 40, the Q value is 1000 to 3000, and the temperature coefficient of resonance frequency (τ
f) has characteristics near 0 ppm / ° C.

[0005]

Recently, there has been a tendency to use higher frequencies and dielectric materials have been required to have more excellent dielectric properties, particularly to improve the Q value. However, in the conventional dielectric material described above,
At present, it does not have a practically high Q value in a used frequency region of 10 GHz.

Accordingly, an object of the present invention is to provide a novel high-frequency dielectric ceramic composition having a high dielectric constant and a high Q value in a high-frequency region capable of meeting such requirements.

[0007]

Means for Solving the Problems The present inventors have studied the above problems and found that BaO, MgO, WO
₃ , and the composition formula based on the molar ratio is xBaO.yMgO.
When expressed as · Zwo _3, wherein x, y, z is 0.40 ≦ x
≦ 0.55, 0.15 ≦ y ≦ 0.40, 0.20 ≦ z ≦
It has been found that by setting the composition range to satisfy 0.30, excellent dielectric properties can be obtained.

The dielectric porcelain composition of the present invention is composed of a metal composite oxide and is composed of BaO, MgO and WO ₃ , and their composition ranges are shown in the ternary diagram of FIG. In FIG. 1, a region surrounded by points abcda, that is, a composition formula based on a molar ratio is represented by xBaO ·
When expressed as yMgO · zWO ₃ , the values of x, y, and z are equal to 0.
40 ≦ x ≦ 0.55, 0.15 ≦ y ≦ 0.40, 0.2
This is set in a region satisfying 0 ≦ z ≦ 0.30.

The reason for setting these ratios in the above range is that if the BaO content (x) is less than 0.40, the Q value decreases, and if it exceeds 0.55, sintering becomes difficult.
On the other hand, if the amount of MgO (y) is less than 0.15, sinterability becomes difficult, or the Q value is reduced. If it is more than 0.40, the Q value is reduced. Further, when the WO ₃ amount (z) is 0.
If it is less than 20, the sinterability decreases, and if it is more than 0.30, the Q value decreases.

The high frequency dielectric ceramic composition of the present invention comprises BaO, MgO, and WO ₃ , which are expressed as Ba (Mg _1/2 W _1/2 ) O ₃ as a crystal phase. The main perovskite-type crystal phase is a main crystal phase. That is, in the perovskite crystal structure, the A site is made of Ba and the B site is made of Mg and W in a ratio of 1: 1.

As a method for producing a porcelain based on the present invention, for example, an oxide of Ba, Mg, or W or a metal salt such as a carbonate or a nitrate which forms an oxide upon firing is used as a raw material, and these are used in the above-described range. After weighing, mix well. Then, the mixture is 900-110
Calcination at 0 ° C and pulverization. Then, the calcined powder is formed into a predetermined shape by a forming method such as press forming or a doctor blade method.

Next, the molded body is fired at 1300 to 1600 ° C. in an oxidizing atmosphere such as the air to obtain a relative density of 9%.
0% or more of dielectric porcelain can be obtained.

[0013]

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 MgCO ₃ and WO ₃ powders,
The mixture was weighed to the ratio shown in Table 1 and put into a ball mill lined with rubber together with water and wet-mixed for 8 hours. Next, after dehydrating and drying the mixture, it was calcined at 1000 ° C. for 2 hours, and the calcined product was wet-pulverized for 8 hours by putting water and an organic binder into a ball mill.

[0015] Then, after drying the pulverized material, the pulverized product was granulated through a No. 50 mesh net, and the obtained powder was 2,000 milled.
It was formed into a disk having a size of 10 mmφ × 5 mmt under a pressure of kg / cm ² . Furthermore, this disk is
It was fired under the condition of 50 ° C. × 6 hours to obtain a porcelain sample.

With respect to the porcelain sample thus obtained, the relative dielectric constant (εr) and Q value at a frequency of 10 GHz were measured by the dielectric resonator method, and the temperature change of the resonance frequency in the temperature range from 25 ° C. to 85 ° C. The temperature coefficient (τf) of the resonance frequency was calculated from the ratio. The results are shown in Table 1.

[0017]

[Table 1]

According to Table 1, Sample No. _{3 in which} the composition of BaO, MgO and WO _{3 is out} of the range of the present invention. 4, 5,
Samples 6, 7, 8, and 9 had a Q value of 100 or less or caused sintering failure. In contrast, the sample of the present invention achieves a relative dielectric constant of 15 or more, a Q value of 3000 or more, and a temperature coefficient of resonance frequency of 30 ppm / ° C. or less in absolute value.
Sample N in which O: WO ₃ has a ratio of 1: 0.5: 0.5
o. 10 shows particularly excellent characteristics, and has a dielectric constant of 20 and a Q value of 1
Over 3000 have been achieved.

Therefore, the sample No. X for 10 porcelain
A line diffraction measurement was performed, and the results are shown in FIG. According to FIG. 2, it can be understood from the peaks indicated by the circles that the crystal structure is a perovskite crystal structure, and the composition formula thereof is Ba (Mg _1/2 W).
It is estimated to be _1/2) O _3. Further, it is understood from the peaks indicated by ● that a superlattice structure is formed by a regular arrangement of Mg and W.

[0020]

As described in detail above, according to the present invention, B
By mixing aO, MgO and WO ₃ at a predetermined ratio, a high dielectric constant and a high Q value can be obtained in a high frequency region. Thereby, it can be sufficiently applied to a resonator material and a MIC dielectric substrate material used in a microwave or millimeter wave region.

[Brief description of the drawings]

[1] BaO-MgO-WO _{3 3} indicating the scope of the present invention
It is an original figure.

FIG. 2 shows sample Nos. 10 is an X-ray diffraction chart of FIG.

Continuation of the front page (56) References Soviet Physics: -Crstalography, Vol. 2, 9 October 1974, p. 236

Claims (1)

(57) [Claims] 1. A composition comprising BaO, MgO, and WO ₃ , wherein x is represented by the formula xBaO.yMgO.zWO ₃ ,
A dielectric ceramic composition for high frequency waves, wherein y and z satisfy 0.40 ≦ x ≦ 0.55 0.15 ≦ y ≦ 0.40 0.20 ≦ z ≦ 0.30.