JPH09263449A - High frequency dielectric ceramic composition - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To control wide range of temperature coefficient (τf) of resonance frequency continuously from minus side to plus side while having high relative permittivity and high Q value in microwave and millimeter wave regions. A high frequency dielectric ceramic composition capable of obtaining a possible dielectric material. A composition formula based on a molar ratio is x {(1-a) Ba.
When expressed as O.aCaO} .yMgO.zWO ₃ , a,
x, y and z are 0 <a <1, 0.40 ≦ x ≦ 0.55,
0.15 ≦ y ≦ 0.30, 0.20 ≦ z ≦ 0.30, x
+ Y + z = 1 at the same time, (Ba _1-a Ca
_a ) In the perovskite type crystal represented by (Mg _1/2 W _1/2 ) O ₃ , the crystal phase with 0 <a <1 is the main crystal phase.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD 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 ceramic composition suitable for high-frequency electronic components such as the above, a dielectric substrate for MIC, 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, under the present circumstances, the above-mentioned conventional dielectric material does not have a practically high Q value (Qf = 15000 or less) in the operating frequency region of 10 GHz.

The present inventors have found that BaO, M as a composition 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 CaO, MgO, and WO ₃ have been previously proposed (Japanese Patent Laid-Open No. 5-205524, Japanese Patent Application No. 8-50118).

However, although a high Q value can be obtained with these dielectric ceramic compositions, the temperature coefficient (τf) of the resonance frequency is too negatively biased, so that when used as a microwave dielectric material, There was a problem in practical use, such as limited fields of use.

[0008]

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 types of oxides should be compounded, that is, BaO, CaO, Mg.
It consists of O and WO ₃ , and the composition formula based on the molar ratio is x {(1-
a) when expressed as BaO · aCaO} · yMgO · zWO 3, a, x, y, z is 0 <a <1,0.40 ≦ x ≦ 0.
55, 0.15 ≦ y ≦ 0.30, 0.20 ≦ z ≦ 0.3
0, x + y + z = 1 at the same time, the composition range is satisfied, and (Ba _1-a Ca _a ) (Mg _1/2 W _1/2 )
Excellent dielectric properties can be obtained by using a perovskite type crystal (0 <a <1) represented by O ₃ as a main crystal phase, and a temperature coefficient of resonance frequency can be obtained by appropriately setting a within a predetermined range. The present invention has been completed by finding that (τf) can shift from the minus side to the plus side.

That is, the high-frequency dielectric ceramic composition of the present invention contains Ba, Ca, Mg, and W as metal elements, and the composition formula based on the molar ratio of these metal element oxides is x {(1
-A) when expressed as BaO · aCaO} · yMgO · zWO 3, wherein a, x, y, z are, 0 <a <1,0.40 ≦
x ≦ 0.55, 0.15 ≦ y ≦ 0.30, 0.20 ≦ z
It satisfies ≦ 0.30 and x + y + z = 1. Here, it is desirable that the perovskite type crystal (0 <a <1) represented by (Ba _1-a Ca _a ) (Mg _1/2 W _1/2 ) O ₃ be the main crystal phase.

[0010]

According to the dielectric ceramic composition of the present invention, the composition formula is x
{(1-a) BaO ・ aCaO} ・ yMgO ・ zWO ₃
In the composition represented by, by changing the molar ratio of BaO and CaO, the temperature coefficient (τ
f) can be freely controlled in a constant region from the minus side to the plus side.

In the dielectric porcelain composition of the present invention, as shown in FIG. 1, 2 has a resonance frequency temperature coefficient (τf) of 0.
Since there are dots, it is possible to easily control the temperature coefficient (τf).

For example, BaO: MgO: WO ₃ = 2:
In the porcelain composition (BMW) consisting of 1: 1 (molar ratio),
Dielectric constant of 20 and Q value of 13000 at 10 GHz measurement frequency
However, the temperature coefficient (τf) of the resonance frequency is −
30 ppm / ° C, large on the negative side. Also, CaO:
A porcelain composition (CMW) composed of MgO: WO ₃ = 2: 1: 1 (molar ratio) shows a high relative permittivity of 18 and a Q value of 7500 at a measurement frequency of 10 GHz, but the temperature coefficient of resonance frequency (τf ) Is -90 ppm / ° C, which is large on the negative side. The temperature coefficient (τf) of the resonance frequency is increased from −95 ppm / ° C. to + by solid-dissolving Ba and Ca according to the present invention.
It is possible to continuously control up to 45 ppm / ° C.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The high frequency dielectric ceramic composition of the present invention is composed of BaO, CaO, MgO and WO ₃ , and (1-a) BaO.aCaO, MgO and WO ₃ are predetermined. For each a of 0 <a <1, 0.40 ≦ x ≦ 0.55, 0.15 ≦ y ≦ 0.3
0, 0.20 ≦ z ≦ 0.30 are simultaneously set in the area.

The reason why 0 <a <1 in these composition ratios is that
This is because when a = 0 and 1, solid solutions of Ba and Ca cannot be obtained, and the effect of controlling the temperature coefficient (τf) of the resonance frequency cannot be obtained. Further, the composition ratio is limited to the above range for each a because the effect of solid solution is insufficient outside the above range,
Another problem is that the sinterability and the Q value decrease.

That is, the molar ratio is set to 0.40≤x≤0.55, because when it is smaller than 0.40 or larger than 0.55, sintering becomes defective or the Q value is lowered. Because it does. x is 0.48 ≦ x because the Q value is improved.
≦ 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 0.22 ≦ because of the improvement of the Q value and the sinterability.
It is desirable that y ≦ 0.28.

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.

The high frequency dielectric ceramic composition of the present invention comprises BaO, CaO, MgO and WO ₃ , and has a crystalline phase of (Ba _1-a Ca _a ) (Mg).
_The main crystal phase is the perovskite type crystal phase represented by _1/2 W _1/2 ) O ₃ . That is, A site is composed of Ba and Ca with (1-a): a, and B site is composed of Mg and W.
Is a 1: 1 crystal. The material having such a crystal may itself be a polycrystal such as a sintered body or a single crystal. In addition, in the high frequency dielectric ceramic composition of the present invention, (Ba _1-a Ca
_a ) Ba as a crystal phase other than (Mg _1/2 W _1/2 ) O ₃
WO ₄ , BaW ₂ O ₉ , Ba ₂ WO ₅ , CaWO _4, etc. may be present, but there is no problem in terms of characteristics as long as the amount is very small.

The high frequency dielectric ceramic composition of the present invention has a composition formula of x {(1-a) B according to the molar ratio of the metal element oxide.
When expressed as aO · aCaO} · yMgO · zWO ₃ ,
a, x, y, z are 0 <a <1, 0.48 ≦ x ≦ 0.5
2, 0.22 ≦ y ≦ 0.28, 0.22 ≦ z ≦ 0.2
8, it is desirable to satisfy x + y + z = 1.

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 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, the mixture is heated in the atmosphere to 900-
It is calcined at 1200 ° C and crushed.

Then, a predetermined binder or the like is added to the calcined powder, and it is molded into a predetermined shape by a known molding method such as press molding or doctor blade method. Next, the molded body is heated at 1300 to 1550 ° C. for 2 hours in an oxidizing atmosphere such as air.
A dielectric ceramic can be obtained by firing for ~ 6 hours.

In the high frequency dielectric ceramic composition of the present invention,
Cl, Al, P, Na, Sr, Z as unavoidable impurities
In some cases, r, Y, etc. may be mixed in, and even if they are mixed in about 0.1% by weight in the total amount, there is no problem in characteristics. In addition, metal and the like may be mixed from the crushing balls during the mixed crushing.

[0024]

EXAMPLES As raw materials, BaCO ₃ and C with a purity of 99% or more are used.
ACO _3, MgCO ₃ and, using each powder WO _3,
These were weighed in the ratios shown in Table 1 and Table 2, put in a ball mill lined with rubber together with water, and ZrO ₂
Wet mixed with a ball for 8 hours. Next, this mixture was dehydrated and dried, and then calcined in the atmosphere at 1000 ° C. for 2 hours, and the calcined material was wet-ground with a ZrO ₂ ball for 8 hours 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, and the obtained powder was 3000
A cylinder having a diameter of 10 mm and a thickness of 6 mm was formed at a pressure of kg / cm ² . Furthermore, this cylinder is
Firing was performed under the conditions of 300 to 1550 ° C. × 6 hours to produce a porcelain. This porcelain is polished to a diameter of 8 mm and a thickness of 4-5 m.
A sample of size m was obtained.

With respect to the thus obtained porcelain sample, the relative permittivity (εr) and the Q value at a frequency of 10 to 11 GHz were measured by the dielectric resonator method, and regarding the Q value, it was considered that Qf = constant. It was converted to a Q value of 10 GHz. Further, the temperature coefficient (τf) of the TE011 mode resonance frequency from 25 ° C. to 85 ° C. is τf = [(f ₈₅ −f
₂₅ ) / f ₂₅ ] / 60 ° C. × 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 and 2.

[0027]

[Table 1]

[0028]

[Table 2]

According to these Tables 1 and 2, BaO,
Samples having CaO, MgO, and WO _{3 in} a composition outside the range of the present invention had an insufficient effect of controlling the temperature characteristics of the resonance frequency, or had a Q value of 100 or less, or had defective sintering. On the other hand, the sample according to the present invention has a higher Q value than the comparative example, but the temperature coefficient of the resonance frequency can be continuously controlled between −95 ppm / ° C. and +45 ppm / ° C. depending on the value of a. I understand.

In addition, the inventors of the present invention have confirmed that the sample No. Crystals were identified and lattice constants were evaluated for 38 porcelain by X-ray diffraction measurement, and the results are shown in FIG. According to FIG.
It is understood that the perovskite type crystal structure is obtained from the diffraction peaks of the mark,
It is understood that it consists of a superlattice structure with an ordered array of W.

Most of the produced dielectric ceramics of the present invention were composed of (Ba _1-a Ca _a ) (Mg _1/2 W _1/2 ) O ₃ crystal grains, and the average crystal grain size was 3 Was about 7 μm.
In addition, a small amount of phases composed of BaO, CaO and WO ₃ existed at the grain boundaries.

[0032]

As described above in detail, BaO, CaO, M
By blending gO and WO ₃ in a predetermined ratio, the temperature coefficient of the resonance frequency can be continuously and widely controlled from the negative side to the positive side while having a high relative dielectric constant and a high Q value in the high frequency region. A dielectric material can be obtained. As a result, the resonator material used in the microwave or millimeter wave region, the dielectric substrate material for MIC,
It can be sufficiently applied to materials for capacitors, materials for dielectric antennas, materials for dielectric waveguides, and the like.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the solid solution amount a of CaO and the temperature characteristic τf of the resonance frequency in the dielectric ceramic compositions of samples No. 37 to 44 of Table 1 of the present invention.

FIG. 2 shows the sample No. of Table 1 in the example. It is an X-ray diffraction chart of No. 38.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location H01P 7/10 H01P 7/10

Claims (2)

[Claims] 1. A compositional formula containing Ba, Ca, Mg, and W as metal elements and having a molar ratio of these metal element oxides is x {(1-a) BaO.aCaO} .yMgO.zWO.
_When expressed as ₃ , a, x, y, z are 0 <a <1 0.40 ≦ x ≦ 0.55 0.15 ≦ y ≦ 0.30 0.20 ≦ z ≦ 0.30 x + y + z = 1 And a dielectric ceramic composition for high frequency, characterized in that 2. (Ba _1-a Ca _a ) (Mg _1/2 W _1/2 ) O
The high frequency dielectric ceramic composition according to claim 1, wherein a perovskite type crystal (0 <a <1) represented by ₃ is used as a main crystal phase.