JPH09268058A - Dielectric porcelain composition for high frequency wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dielectric porcelain composition for high frequency waves, capable of readily controlling the temperature coefficient of the resonance frequency, providing a sufficient porcelain density and improving the strength and having a high Q value even when baked at low temperatures. SOLUTION: This dielectric porcelain composition for high frequency waves comprises at least Ba, Sr, Mg and W as metallic elements and (a), (b), (x), (y) and (z) satisfy 0<(a)<1, 0.01<=(b)<=0.7, 0.40<=(x)<=0.55, 0.15<=(y)<=0.30, 0.20<=(z)<=0.30 and [(x)+(y)+(z)]=1 when the compositional formula is represented by x (1-a)BaO.aSrO}.y (1-b)MGo.bAO}.zWO3 (A is at least one of an iron family metal and Zn). Furthermore, the dielectric porcelain composition comprises a perovskite type crystal represented by the formula, (Ba1-a Sra ) (Mg1-b Ab )1/2 W1/2 }O3 [0<(a)<1, 0.01<=(b)<=0.7] as the main crystal phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency dielectric ceramic composition having a high relative permittivity and a high Q value in a high frequency region such as a microwave and a millimeter wave, and particularly to a dielectric resonator, a filter and a capacitor. The present invention relates to a high-frequency dielectric porcelain composition suitable for high-frequency electronic components such as MIC dielectric substrates, MIC dielectric substrates, and millimeter-wave waveguides.

[0002]

2. Description of the Related Art Hitherto, dielectric porcelain has been widely used in dielectric resonators, MIC dielectric substrates, and the like in high-frequency regions such as microwaves and millimeter waves. Recently, dielectric waveguides have been applied to millimeter wave waveguides.

[0003] Conventionally, as this kind of dielectric porcelain,
For example, ZrO ₂ —SnO ₂ —TiO ₂ based material, BaO—
TiO ₂ -based materials, (Ba, Sr) (Zr, Ti) O ₃ -based materials and Ba (Zn, Ta) O ₃ -based materials are known, and these materials have a frequency of 500 MHz through various improvements.
In the range of z to 5 GHz, the relative dielectric constant is 20 to 40, and the Q value is 10
It has a characteristic in which the temperature coefficient (τf) of the resonance frequency is around 0 ppm / ° C. (Qf = 15000 or less).

[0004]

However, 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, under the present circumstances, the above-mentioned conventional dielectric material does not have a practically high Q value (Qf = 15000 or less) at a high frequency, for example, a frequency range of 10 GHz.

Further, it is necessary to fire at a high temperature in order to improve the density of the porcelain, and it is difficult to obtain a sufficient porcelain density even when firing at a high temperature, and the strength is weak, and it is difficult to obtain a high Q value. There was a problem.

The inventors of the present invention have reported that BaO, M and M are used as compositions having a high relative dielectric constant and a high Q value in the high frequency region.
A dielectric ceramic composition composed of a composite oxide containing gO and WO ₃ and a dielectric ceramic composition composed of a composite oxide containing SrO, MgO and WO ₃ were previously proposed (Japanese Patent Laid-Open No. 5-205524, JP-A-6-5117).

However, although these dielectric ceramic compositions can obtain a high Q value in a high frequency region, they are used as microwave dielectric materials because the temperature coefficient (τf) of the resonance frequency is too biased to the negative side. In that case, there was a problem in practical use such as limitation of the field of use.

Further, since the firing temperature is high and the manufacturing cost is high, there is a problem in practical use such that the field of use thereof is limited. For example, a porcelain composed of 50 mol% of BaO, 25 mol% of MgO and 25 mol% of WO ₃ shows a high relative dielectric constant of 20 and a Q value of 13000 at a measurement frequency of 10 GHz, but the firing temperature is high at 1600 ° C.

[0010]

Means for Solving the Problems As a result of various studies on the above problems, the present inventors have found that the previously proposed two kinds of oxides should be compounded, that is, BaO, SrO, Mg.
A composition of O and WO ₃ was prepared, and further, cobalt (Co), nickel (Ni), zinc (Z
By containing at least one kind of n) or the like in a predetermined amount, a high Q value can be obtained even if the firing temperature is lowered, and the temperature coefficient (τf) of the resonance frequency can be shifted from the negative side to the positive side. The inventors have found that the porcelain density (bulk specific gravity) can be improved and the porcelain strength can be improved, and the present invention has been accomplished.

That is, the high frequency dielectric porcelain composition of the present invention contains at least Ba, Sr, Mg and W as metal elements, and the composition formula based on the molar ratio of these metal element oxides is x {(1 -A) BaO · aSrO} · y {(1
-B) When expressed as MgO · bAO｝ · zWO ₃ (A is at least one of iron group metals and Zn),
b, x, y and z are 0 <a <1, 0.01 ≦ b ≦
0.7, 0.40 ≦ x ≦ 0.55, 0.15 ≦ y ≦ 0.
30, 0.20 ≦ z ≦ 0.30, x + y + z = 1. Here, the general formula (Ba _1-a Sr _a )
_{{(Mg 1-b A b} ) 1/2 W 1/2} O 3 perovskite crystal represented (0 <a <1,0.01 ≦ b ≦ 0.7)
Is preferably used as the main crystal phase.

[0012]

In the high frequency dielectric ceramic composition of the present invention, the composition formula is x {(1-a) BaO.aSrO} .y {(1-
b) a composition represented as MgO · bAO} · zWO _3, be freely controlled in certain areas of the positive temperature coefficient of resonant frequency (.tau.f) from the negative side by changing the molar ratio of BaO and SrO Cobalt (Co), nickel (Ni), zinc (Z
By containing at least one kind of n) or the like in a predetermined amount, it becomes possible to perform firing at a temperature lower by about 150 ° C. than before, and it is possible to have a high Q value even when the firing temperature is lowered, and to have a high porcelain density. High strength can be realized by (bulk specific gravity).

That is, the main components of BaO, SrO, Mg
By adding a predetermined amount of at least one of cobalt (Co), nickel (Ni), zinc (Zn) and the like to the composition comprising O and WO ₃ , sintering is promoted at a low temperature and high The porcelain strength and high Q value can be obtained.

Conventionally, a composition having a temperature coefficient of positive resonance frequency (τf) is added to a composition having a temperature coefficient of negative resonance frequency (τf) to obtain a temperature of positive resonance frequency. It controlled so that it might have a coefficient ((tau) f). In this case, the temperature coefficient of resonance frequency (τ
There will be one point where f) is 0.

In the present invention, by combining two compositions having a negative resonance frequency temperature coefficient (τf), for example, a dielectric ceramic composition composed of a composite oxide containing BaO-MgO-WO ₃ or , SrO-MgO-WO
_This is based on a completely new technical idea of shifting the temperature coefficient (τf) of the resonance frequency to the positive side, which could not be achieved only by the dielectric ceramic composition composed of the complex oxide containing ₃ . In the dielectric ceramic composition of the present invention, there are two points where the temperature coefficient (τf) of the resonance frequency is 0, and the temperature coefficient of the resonance frequency can be easily controlled.

For example, BaO: MgO: WO ₃ = 2:
In a porcelain composition consisting of 1: 1 (molar ratio), 10 GHz
Shows a high relative permittivity of 20 and a Q value of 13000 at the measurement frequency, but the temperature coefficient (τf) of the resonance frequency is -30pp
It is large on the minus side with m / ° C.

Further, SrO: MgO: WO ₃ = 2: 1:
A porcelain composition consisting of 1 (molar ratio) shows a high relative permittivity of 20 and a Q value of 6000 at a measurement frequency of 10 GHz, but the temperature coefficient (τf) of the resonance frequency is -60 ppm / ° C.
And big on the minus side. By solid-dissolving Ba and Sr according to the present invention, the temperature coefficient (τf) of the resonance frequency is
Can be continuously controlled from −60 ppm / ° C. to +35 ppm / ° C.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The dielectric ceramic composition for high frequencies of the present invention has a compositional formula based on the molar ratio of the metal element oxide, x
{(1-a) BaO.aSrO} .y {(1-b) Mg
O · bAO} · zWO ₃ , the above a, b, x,
y and z are 0 <a <1, 0.01 ≦ b ≦ 0.7, 0.4
0 ≦ x ≦ 0.55, 0.15 ≦ y ≦ 0.30, 0.20
≦ z ≦ 0.30, x + y + z = 1.

Here, the substitution amount a of BaO with SrO is set to 0 <a <1 because the solid solution of Ba and Sr is not obtained at a = 0 and 1, and the temperature coefficient (τf) of the resonance frequency is controlled. This is because the effect cannot be obtained. Further, the substitution amount b of MgO by the iron group metal and Zn is set to 0.01 ≤ b ≤ 0.7, because when b is less than 0.01, the effect of lowering the firing temperature and improving the porcelain density is almost obtained. However, when it is more than 0.7, the Q value is remarkably reduced. This b is 0.01 ≦ from the viewpoint of obtaining a higher porcelain density and a high Q value.
It is desirable that b ≦ 0.65. The iron group metals include Fe, Ni, and Co, but among these, N
i and Co are desirable.

Further, the reason why the composition ratio for each of a and b is limited to the above range is that the effect of solid solution is insufficient outside the above range, or the sinterability and Q value decrease. This is because problems will occur.

That is, the molar ratio x is 0.40≤x≤0.55
This is because the Q value decreases when the value is smaller than 0.40 or larger than 0.55. x is
For improving the Q value, 0.49 ≦ x ≦ 0.52 is desirable.

Further, the molar ratio of MgO is 0.15 ≦ y ≦
The reason for setting 0.30 is that when y is smaller than 0.15, the Q value is lowered, and when y is larger than 0.30, the Q value is lowered and sintering becomes defective. The molar ratio y of MgO is 0.20 ≦ because of the improvement of the Q value and the sinterability.
It is desirable that y ≦ 0.27.

Further, the molar ratio of WO ₃ is 0.20 ≦ z ≦.
The reason for setting it to 0.30 is that if z is smaller than 0.20, the sintering becomes defective, and if it is larger than 0.30, the Q value decreases. The molar ratio z of WO ₃ is preferably 0.22 ≦ z ≦ 0.28 in order to improve the Q value and sinterability.

In the high frequency dielectric ceramic composition of the present invention, the composition formula is x {(1-a) BaO.aSrO} .y {(1
-B) When expressed as MgO · bAO｝ · zWO ₃ , a,
b, x, y, z are 0 <a <1, 0.01 ≦ b ≦ 0.6
5, 0.49 ≦ x ≦ 0.52, 0.20 ≦ y ≦ 0.2
7, it is desirable that 0.22 ≦ z ≦ 0.28 and x + y + z = 1 be satisfied.

As a method for producing a porcelain based on the present invention, for example, an oxide of Ba, Sr, Mg, W or a metal salt such as a carbonate or a nitrate which produces an oxide by firing is prepared as a main raw material. Is weighed so as to fall within the above range, and then thoroughly mixed.

Then, in the atmosphere, 900 to 1200
Calcination is performed at ℃ for 1 to 4 hours.

The obtained calcined product is added to, for example, a cobalt compound such as CoO, a nickel compound such as NiO, Z
Each zinc compound such as nO is weighed and added to a predetermined amount, and mixed and ground. Then, this is molded into a predetermined shape by a molding method such as press molding or a doctor blade method. Next, the molded body is fired in an oxidizing atmosphere such as the air at 1300 ° C. to 1450 ° C. for 1 to 8 hours to obtain a dielectric ceramic.

In the present invention, C is an unavoidable impurity.
l, Ca, Zr, etc. may be mixed, and Cl, C
Even if a, Zr, etc. are mixed in an amount of about 0.1% by weight in terms of oxide, there is no problem in characteristics. In particular, for the dielectric composition, Al
Since the presence of each element of Y and Y tends to increase the firing temperature, according to the present invention, the amounts of these metal elements are:
It is desirable to control the total amount of oxides including impurities to be 5% by weight or less.

In the present invention, the general formula (Ba
_1-a Sr _a ) {(Mg _1-b A _b ) _1/2 W _1/2 } O ₃ perovskite type crystal (0 <a <1, 0.01 ≦
It is desirable that b ≦ 0.7) be the main crystal, but in addition, even if a small amount of crystals such as BaWO ₄ and SrWO ₄ exist, there is almost no problem in terms of characteristics. .

[0030]

EXAMPLES As raw materials, BaCO ₃ and S having a purity of 99% or more were used.
rCO _3, MgCO _3, CoO (or NiO or ZnO,) and, using the powder of WO _3, it was weighed to a ratio shown in Table 1 to Table 4, which were placed with IPA in a ball mill lined with rubber , ZrO ₂ balls were used for wet mixing for 8 hours. Next, the mixture was desolvated and dried, and then calcined in the air at 1000 ° C. for 2 hours. Put the calcined product in a ball mill with IPA,
Wet milling was carried out for 8 hours using O ₂ balls.

Thereafter, the pulverized product was dried, an organic binder was added, and then the mixture was granulated through a mesh of No. 50 mesh,
The obtained powder was crushed at a pressure of 3000 kg / cm ^{2 to} a diameter of 10
It was formed into a cylinder having a thickness of 5 mm and a thickness of 5 mm. Further, the column was fired in the atmosphere at 1300 to 1600 ° C. for 2 to 6 hours to obtain a porcelain. The porcelain was polished to obtain a sample having a diameter of 8 mm and a thickness of 4 to 5 mm.

The porcelain density of the obtained sample was measured by the Archimedes method. Frequency of about 10-11 GHz
The relative permittivity (εr) and the Q value in (1) were measured by the dielectric resonator method, and the Q value was converted into the Q value at 10 GHz, assuming that the general formula Qf = constant. Also 25
The temperature coefficient (τf) of the TE011 mode resonance frequency at each temperature from ℃ to 85 ℃, τf = [(f ₈₅ −
It was calculated based on f ₂₅ ) / f ₂₅ ] / 60 × 10 ⁶ [ppm / ° C.]. Here, f ₈₅ is the resonance frequency at 85 ° C., and f ₂₅ is the resonance frequency at 25 ° C. The results are shown in Tables 1, 2, 3, and 4.

The obtained porcelain was subjected to X-ray diffraction measurement. As a result, in the sample of the present invention, the general formula (Ba _1-a S
r _a ) {(Mg _1-b A _b ) _1/2 W _1/2 } O ₃ perovskite type crystal (0 <a <1, 0.01 ≦ b ≦
It was confirmed that 0.7) was the main crystal phase.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

From these tables, in the high frequency dielectric ceramic composition of the present invention, the temperature coefficient (τf) of the resonance frequency can be easily controlled and the iron group metal by changing the value of a. By including at least one of Zn and Zn, the sintering temperature can be set to 150
It is possible to lower the temperature by about 0 ° C., and even when the composition is fired at a low temperature, the porcelain density of the composition is improved, the strength can be increased, and the Q value at 10 GHz can be increased to 2500 or more.

[0039]

In the high frequency dielectric ceramic composition of the present invention, the iron group metal and zinc are contained in the predetermined amounts with respect to the main components of BaO, SrO, MgO and WO _3, so that the resonance frequency temperature The coefficient (τf) can be controlled easily, and the sintering temperature is set to 150 compared with the conventional one.
C., and even in this case, the porcelain density of the composition can be improved and the strength can be increased to 10 GH.
The Q value at z can be as high as 2500 or more. The porcelain obtained in this way should be sufficiently applied to resonator materials used in microwave and millimeter wave regions, MIC dielectric substrate materials, capacitor materials, dielectric antenna materials, dielectric waveguide materials, etc. Can be.

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Claims (2)

[Claims] 1. A metal element containing at least Ba, Sr, and M.
g and W, and the composition formula based on the molar ratio of these metal element oxides is x {(1-a) BaO.aSrO} .y {(1-b) M
gO · bAO} · zWO ₃ (A is at least one of an iron group metal and Zn), a, b, x, y and z are 0 <a <1 0.01 ≦ b ≦ 0.7. 0.40 ≦ x ≦ 0.55 0.15 ≦ y ≦ 0.30 0.20 ≦ z ≦ 0.30 x + y + z = 1 The high frequency dielectric ceramic composition. 2. The general formula (Ba _1-a Sr _a ) {(Mg _1-b A
_2. The high frequency dielectric according to claim 1, wherein a perovskite type crystal (0 <a <1, 0.01 ≦ b ≦ 0.7) represented by _b ) _1/2 W _1/2 } O ₃ is used as a main crystal phase. Body porcelain composition.