JPH10162649A - Dielectric porcelain composition - Google Patents

Abstract

(57) [Problem] To provide a dielectric ceramic composition which can easily control the temperature coefficient of resonance frequency, can be fired at a low temperature, and has a high Q value even when fired at a low temperature. The composition formula is represented by x を (1-a) BaO · aCa.
O｝ .y ｛(1-b) MgO.bAO｝ .zWO ₃ (A
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.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition having a high relative dielectric constant and a high Q value in a high frequency region such as a microwave and a millimeter wave, and more particularly, to a dielectric resonator,
High frequency electronic components and MICs such as filters and capacitors
The present invention relates to a high frequency dielectric ceramic composition suitable for a dielectric substrate for millimeter waves and a waveguide for millimeter waves.

[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, at present, the above-mentioned conventional dielectric materials do not have a practically high Q value at a high frequency, for example, an operating 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.

As a composition that solves such a problem, the present inventors have proposed x ｛(1-a) B as a composition having a high relative dielectric constant and a high Q value in a high-frequency region.
A dielectric porcelain composition comprising aO.aCaO｝ .yMgO.zWO ₃ was previously proposed (Japanese Patent Application No. 8-73888).
issue).

Although this dielectric porcelain composition has excellent dielectric properties such as a high Q value in a high frequency range, it has a problem that the firing temperature is high, so that the production cost is high and the field of application is limited. Was. For example, in the above composition formula, x = 0.42, y = 0.28, z = 0.
3. In the case of porcelain with a = 0.1, the relative dielectric constant and Q value are as high as 15 and 10700 at the measurement frequency of 10 GHz.
The firing temperature is as high as 1600 ° C.

[0009]

The present inventors have conducted various studies on the above problems and found that BaO, CaO, M
For those consisting of gO and WO ₃ , cobalt (C
o), by containing at least one kind of nickel (Ni), zinc (Zn), and the like in a predetermined amount, the firing temperature can be lowered, and it has been found that a high Q value is obtained even when the firing temperature is lowered. Invented the invention.

That is, the high frequency dielectric ceramic composition of the present invention contains at least Ba, Ca, Mg and W as metal elements, and a composition formula based on the molar ratio of these metal element oxides is expressed as x ｛(1 -A) BaO · aCaO｝ · 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.

[0011]

According to the dielectric ceramic composition of the present invention, the composition formula is x
{(1-a) BaO.aCaO} .y {(1-b) Mg
In a composition represented by O.bAO｝ .zWO ₃ ,
By changing the molar ratio of aO and CaO, the temperature coefficient (τf) of the resonance frequency can be freely controlled in a certain region from the minus side to the plus side, and cobalt (Co), nickel (Ni), zinc ( By including at least one kind of Zn) or the like in a predetermined amount, it is possible to fire at a temperature lower by about 100 ° C. than in the past, and to have a high Q value even when the firing temperature is lowered,
High strength due to high porcelain density (bulk specific gravity) can be realized.

That is, the main components BaO, CaO, 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 positive temperature coefficient of resonance frequency (τf) is added to a composition having a temperature coefficient of negative resonance frequency (τf) to obtain a temperature coefficient of positive resonance frequency. Control was performed so as to have a coefficient (τf). In this case, since the coefficient almost linearly increases from the negative side to the positive side, there is one point where the temperature coefficient (τf) of the resonance frequency is 0.

In the present invention, by combining two compositions having a temperature coefficient (τf) of a negative resonance frequency, for example, a dielectric ceramic composition comprising a composite oxide containing BaO—MgO—WO ₃ , , CaO-MgO-WO
_This is based on the 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 composite oxide containing ₃ . In the dielectric porcelain composition of the present invention, the temperature coefficient has a curved shape protruding from the minus side to the plus side, and there are two points where the temperature coefficient (τf) of the resonance frequency is 0. Can be easily controlled.

For example, BaO: MgO: WO ₃ = 2:
In a porcelain composition consisting of 1: 1 (molar ratio), 10 GHz
It shows a high value of relative permittivity of 20 and a Q value of 15000 at the measurement frequency, but the temperature coefficient (τf) of the resonance frequency is -30 pp
It is large on the minus side with m / ° C.

Further, CaO: MgO: WO ₃ = 2: 1:
The porcelain composition composed of 1 (molar ratio) has a high relative dielectric constant of 18 and a Q value of 7500 at a measurement frequency of 10 GHz, but has a temperature coefficient of resonance frequency (τf) of −90 ppm / ° C.
And big on the minus side. By changing the ratio of Ba and Ca according to the present invention, the temperature coefficient of the resonance frequency (τ
f) can be continuously controlled from about -80 ppm / ° C. to about +40 ppm / ° C.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The dielectric porcelain composition of the present invention is represented by the following formula: x ｛(1-a)
BaO ・ aCaO｝ ・ y ｛(1-b) MgOｂbAO｝
· Zwo ₃ and when expressed, a, b, x, y , z are, 0 <a
<1, 0.01 ≦ b ≦ 0.7, 0.40 ≦ x ≦ 0.5
5, 0.15 ≦ y ≦ 0.30, 0.20 ≦ z ≦ 0.3
0, x + y + z = 1.

The reason why the replacement amount a of BaO by CaO is 0 <a <1 is that the temperature coefficient (τf) of the resonance frequency cannot be controlled when a = 0 and 1. Also, M
The substitution amount b of gO with the iron group metal and Zn is 0.01 ≦
The reason for b ≦ 0.7 is that if b is less than 0.01, the effect of lowering the firing temperature and improving the porcelain density is hardly obtained,
This is because when the number is larger, the Q value is significantly reduced. This b
Is preferably 0.01 ≦ b ≦ 0.65 from the viewpoint of obtaining a higher porcelain density and a higher Q value. Examples of the iron group metal include Fe, Ni, and Co. Of these, Ni and Co are preferable.

The reason why the composition ratio is limited to the above range for each of a and b is that if the ratio is outside the above range, problems such as a decrease in sinterability and a decrease in Q value occur.

That is, when the molar ratio x is 0.40 ≦ x ≦ 0.55
The reason for this is that if the value is smaller than 0.40 or larger than 0.55, the Q value decreases or sintering becomes poor. x is 0.49 ≦ for the reason of improving the Q value.
x ≦ 0.52 is desirable.

Further, the molar ratio of MgO is set to 0.15 ≦ y ≦
The reason for setting 0.30 is that if y is smaller than 0.15, the Q value decreases or sintering becomes poor, and if y is larger than 0.30, the Q value decreases or sintering becomes poor. This is because Desirably, the molar ratio y of MgO satisfies 0.20 ≦ y ≦ 0.27 from the viewpoint of improving the Q value and sinterability.

Further, the molar ratio of WO ₃ is set to 0.20 ≦ z ≦
The reason for setting the value to 0.30 is that when z is smaller than 0.20, sintering becomes defective, and when z is larger than 0.30, the Q value decreases. The molar ratio z of WO ₃ is preferably 0.22 ≦ z ≦ 0.28 from the viewpoint of improving the Q value and sinterability.

In the high frequency dielectric ceramic composition of the present invention, the composition formula is represented by x {(1-a) BaO.aCaO} .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, Ca, Mg, W or a metal salt such as a carbonate or a nitrate which forms an oxide upon firing is prepared as a main raw material. Is weighed so as to be in the above-mentioned range, and then thoroughly mixed.

Thereafter, a calcination treatment is performed at 900 to 1200 ° C. for 1 to 4 hours in an oxidizing atmosphere such as the air.

The obtained calcined product may contain, for example, a cobalt compound such as CoO, a nickel compound such as NiO, Z
Each compound such as a zinc compound such as nO is weighed and added so as to have a predetermined amount, and mixed and pulverized. Incidentally, a cobalt compound such as CoO or the like may be added and calcined and mixed without calcining the main raw material. Then, this is molded into a predetermined shape by a known 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 used as 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 so that the content is 5% by weight or less of the total amount in terms of oxide, including impurities.

In the dielectric porcelain composition of the present invention, the formula (Ba) ｛(Mg ₁ -bA _b ) _1/2 W _1/2 ｝ O
Perovskite type crystal represented by ₃ (0.01 ≦ b ≦
0.7) as the main crystal.

[0029]

EXAMPLES As raw materials, BaCO ₃ and C with a purity of 99% or more are used.
_{aCO 3, MgCO 3, CoO,} NiO, ZnO and W
Using each powder of O ₃ , these were weighed to the ratios shown in Tables 1 to 4, and were weighed in a ball mill lined with rubber.
And wet-mixed for 8 hours using a ZrO ₂ ball. Next, the mixture was desolvated and dried, and then calcined in the air at 1000 ° C. for 2 hours. The calcined product was put into a ball mill together with IPA, and wet-ground with ZrO ₂ balls for 8 hours.

Thereafter, the pulverized product was dried, an organic binder was added, and the granulated product was granulated through a No. 50 mesh net.
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.

For the obtained sample, the frequency was about 10 to 1
The relative dielectric constant (εr) and Q value at 1 GHz were measured by the dielectric resonator method, and the Q value was converted to a Q value at 10 GHz assuming that the general formula Qf = constant.
TE011 at each temperature from 25 ° C. to 85 ° C.
The temperature coefficient (τf) of the mode resonance frequency is given by τf = [(f
₈₅₋ 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 sample was subjected to an X-ray diffraction measurement. As a result, the sample of the present invention was found to have the general formula (Ba)
It was confirmed that a perovskite crystal (0.01 ≦ b ≦ 0.7) represented by ｛(Mg _{1-b Ab} ) _1/2 W _1/2 ｝ O ₃ was used as a main crystal phase.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

From these tables, it is found that the dielectric ceramic composition of the present invention can easily control the temperature coefficient (τf) of the resonance frequency by changing the value of a, By including at least one of Zn, the sintering temperature can be reduced by about 100 ° C. or more than that of a conventional composition containing no Zn, and the porcelain density of the composition can be reduced even when firing at such a low temperature. The strength can be improved and the strength can be improved, and the Q value at 10 GHz can be 2600 or more.

[0038]

According to the dielectric ceramic composition of the present invention, Ba is used.
By containing a predetermined amount of iron group metal and zinc with respect to the main component consisting of O, CaO, MgO and WO ₃ ,
The temperature coefficient (τf) of the resonance frequency can be easily controlled, and the sintering temperature can be reduced by about 100 ° C. as compared with the conventional case. Even in this case, the porcelain density of the composition is improved, and the strength is increased. And the Q value at 10 GHz can be increased to 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.

Claims (1)

[Claims] (1) at least Ba, Ca, M as a metal element;
g and W, and the composition formula based on the molar ratio of these metal element oxides is expressed as x {(1-a) BaO.aCaO} .y {(1-b) M
When expressed as gO · bAO｝ · zWO ₃ (A is at least one of iron group metals 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.