JPH10101425A - Piezoelectric porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dielectric porcelain composition capable of providing a high value of Q and a high porcelain density even when the baking temperature is reduced. SOLUTION: This piezoelectric porcelain composition comprises Ca, Mg and W as metallic elements and (a), (x), (y) and (z) satisfy 0.01<=(a)<=0.80; 0.40<=(x)<=0.55; 0.15<=(y)<=0.30; 0.20<=(z)<=0.30 and [(x)+(y)+(z)]=1 when the compositional formula expressed in terms of molar ratio is represented by xCaO.y[(1-a)MgO.aAO].zWO3 (A is at least one of iron family metals and Zn). A perovskite type crystal represented by the formula Ca (Mg1-a Aa )1/2 W1/2 }O3 is preferably a main crystalline phase [0.01<=(a)<=0.80].

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 high frequency dielectric such as a dielectric resonator, a filter and a capacitor. The present invention relates to a dielectric porcelain composition suitable for electronic parts for use, MIC dielectric substrates, millimeter wave waveguides, and the like.

[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. 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 of 00 to 3000 (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 conventional dielectric materials described above do not have a practically high Q value in the operating frequency range of 10 GHz.

The present inventors have proposed CaO, Mg as a composition having a high relative dielectric constant and a high Q value in a high frequency range.
A dielectric porcelain composition comprising a composite oxide containing O and WO ₃ was previously proposed (Japanese Patent Application No. 8-50118).

[0007] However, although a high Q value can be obtained with this dielectric porcelain composition, the firing temperature is high and the production cost is high. For example, CaO 50 mol%, MgO 25
In the porcelain consisting mol%, WO ₃ 25 mol%, 10GH
At a measurement frequency of z, the dielectric constant is 19 and the Q value is as high as 7500, but the firing temperature is as high as 1500 ° C.

[0008]

The present inventors have conducted various studies on the above problems and found that CaO, MgO, W
By adding at least one element of the iron group metal and Zn at a predetermined ratio to the composition comprising O ₃ , the Q value is high, and the porcelain density is increased even when the firing temperature is lowered. The present inventors have found that they can do so, and have reached the present invention.

That is, the dielectric ceramic composition of the present invention contains at least Ca, Mg, and W as metal elements, and the molar ratio composition formula of these metal element oxides is xCaO · y.
When expressed as [(1-a) MgO.aAO] .zWO ₃ (A is at least one of iron group metals and Zn), a, x, y and z are 0.01 ≦ a ≦ 0. 80,
0.40 ≦ x ≦ 0.55, 0.15 ≦ y ≦ 0.30,
0.20 ≦ z ≦ 0.30, x + y + z = 1. Here, the general formula _{Ca {(Mg 1-a A} a) 1/2
Perovskite crystal represented by W _{1/2 1 /} 2O ₃ (0.0
(1 ≦ a ≦ 0.80) is desirably the main crystal.

[0010]

The dielectric ceramic composition of the present invention has a predetermined molar ratio of C
aO, MgO, and WO _{3 as} main components, and iron group metals and Z
By including the divalent metal of n, the Q value can be maintained high, and the firing temperature can be lowered by about 100 ° C. as compared with a case where the iron group metal or the divalent metal of Zn is not added.

Further, even when the firing temperature is lowered by about 100 ° C. as compared with the case where no iron group metal or a divalent metal such as Zn is added, the Q value is equal to or higher than that when firing at a high temperature, and the porcelain density is high. Can be made equal to or more than that of the related art, and higher strength can be achieved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The dielectric porcelain composition of the present invention has a composition represented by a molar ratio of a metal element oxide represented by xCaO · y.
When expressed as [(1-a) MgO.aAO] .zWO ₃ (A is at least one of iron group metals and Zn), the a, x, y, and z are 0.01 ≦ a ≦ 0. 80, 0.4
0 ≦ x ≦ 0.55, 0.15 ≦ y ≦ 0.30, 0.20
≦ z ≦ 0.30, x + y + z = 1.

Here, the molar ratio of CaO in the above composition formula is set to 0.40 ≦ x ≦ 0.55 because x is 0.40 ≦ x ≦ 0.50.
If it is smaller than 0.55, or if it is larger than 0.55, the Q value will decrease or low-temperature firing will not be possible. It is preferable that x satisfies 0.48 ≦ x ≦ 0.52 from the viewpoint of improving the Q value.

The reason why the molar ratio y of [(1-a) MgO.aAO] is set to 0.15 ≦ y ≦ 0.30 is that y is 0.1.
If the value is smaller than 15, the Q value will decrease or low-temperature sintering will not be possible, and if it is greater than 0.30, the Q value will decrease or sintering will be defective. It is desirable that y satisfies 0.24 ≦ y ≦ 0.28 from the viewpoint of improving the Q value and sinterability.

When the molar ratio z of WO ₃ is 0.20 ≦ z ≦ 0.3
0 is set when z is smaller than 0.20 or 0.3.
This is because if it is larger than 0, the Q value decreases or low-temperature firing cannot be performed. z is set to 0. 0 because the Q value is improved.
It is desirable that 22 ≦ y ≦ 0.28.

According to the present invention, the above CaO-MgO-W
By adding at least one of the iron group metal and Zn to the O ₃ -based composition, the firing temperature can be lowered by about 100 ° C. The iron group metals include Fe, Ni, and Co, and among these, N
i and Co are desirable.

The composition formula xCaO.y [(1-a) M
against gO · aAO] · zWO _3, 0.01 ≦ a ≦
The reason for setting the ratio to 0.80 is that when the ratio is smaller than 0.01, there is almost no effect of adding these elements. On the other hand, when the value is larger than 0.80, the Q value decreases. From the viewpoint that the Q value is not reduced by the addition of the iron group metal and Zn, it is preferable that 0.01 ≦ a ≦ 0.40. Two or more of the iron group metals and Zn may be used. In this case, the total amount falls within the range of 0.01 ≦ a ≦
0.80 should be satisfied.

In the present invention, the composition formula is xCaO · y [(1
-A) MgO · aAO] · zWO ₃ (A is at least one of iron group metals and Zn), a, x,
y and z are 0.01 ≦ a ≦ 0.40, 0.48 ≦ x ≦ 0.
52, 0.24 ≦ y ≦ 0.28, 0.22 ≦ z ≦ 0.2
8, it is desirable to satisfy x + y + z = 1.

Further, the dielectric porcelain composition of the present invention comprises Ca
The main crystal is a perovskite crystal (0.01 ≦ a ≦ 0.80) represented by [(Mg _1−a A _a ) _1/2 W _1/2 ] O ₃ . That is, the crystal has the A site composed of Ca and the B site composed of (Mg + A) and W at a ratio of 1: 1. The material having such a crystal may be in any form of a polycrystal such as a sintered body or a single crystal.

In the dielectric porcelain composition of the present invention, Ca
[(Mg _1-a A _a ) _1/2 W _1/2 ] CaWO ₄ , CaW ₂ O ₉ , Ca ₂ WO _{5 and the} like may be present as crystal phases other than O ₃ , There is no problem in characteristics.

According to the method of manufacturing a porcelain based on the present invention, first, an oxide such as Ca, Mg, W, Co, Ni or Zn or a metal salt such as a carbonate or a nitrate which forms an oxide by firing is prepared. After they are weighed so as to be in the above-mentioned range, they are sufficiently mixed. Then, the mixture is 900
Calcinate at ~ 1200 ° C and pulverize. Then, a predetermined binder or the like is added to the calcined powder, and the powder is formed into a predetermined shape by a known molding method such as press molding or a doctor blade method. Next, the molded body is placed in an oxidizing atmosphere such as air.
By firing at 00 to 1450 ° C. for 1 to 8 hours, a dielectric porcelain can be obtained.

In the dielectric porcelain composition of the present invention, Cl, Al, P, Na, Sr, Zr, Y and the like may be mixed as unavoidable impurities. There is no problem in characteristics. In addition, metal or the like may be mixed in the crushed balls during crushing.

[0023]

EXAMPLES CaCO ₃ , M with a purity of 99% or more as raw materials
Using gCO ₃ , WO ₃ and metal oxide powders of Co, Ni and Zn, these were weighed to the ratios shown in Tables 1 to 4,
This was put together with IPA in a ball mill lined with rubber, and mixed for 18 hours using ZrO ₂ balls. Next, after drying this mixture, it is calcined in the air at 1000 ° C. for 2 hours.
Milled for 8 hours.

Thereafter, the pulverized product was dried, an organic binder was added, and the mixture was granulated through a No. 40 mesh net.
The obtained powder was crushed at a pressure of 3000 kg / cm ^{2 to} a diameter of 10
mm and a thickness of 5 mm. Further, the column was fired at the temperature shown in Tables 1 to 6 for 6 hours to obtain a porcelain sample.

The bulk density of the thus obtained porcelain sample was measured in accordance with JIS C2141-1992 (Testing method for ceramic materials for electrical insulation). The relative dielectric constant (εr) and Q value at a frequency of about 11 GHz were measured by the dielectric resonator method, and the Q value was converted to a Q value at 10 GHz on the assumption that the general formula Qf = constant. TE at each temperature from 25 ° C to 85 ° C
The temperature coefficient (τf) of the 011 mode resonance frequency is represented 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 to 4.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

The obtained porcelain was subjected to X-ray diffraction measurement. As a result, the sample of the present invention was found to have the general formula Ca ｛(Mg)
_{1-a Aa} ) It was confirmed that a perovskite crystal represented by _1/2 W _1/2 ｝ O ₃ was used as a main crystal phase.

According to Tables 1 and 2, when the amount a of the iron group metal and Zn is added, firing can be performed at low temperature, and even when firing at low temperature, the bulk density is high, and the Q value is 3300 or more. It turns out that it is. In particular, a is 0.01
It can be seen that in the case of ~ 0.4, the Q value can be improved as compared with the case where no iron group metal, Zn or the like is added.

According to Table 3, CaO, MgO, W
No. _{3 having} a composition of O ₃ outside the scope of the present invention. In the case of 65 to 85, the Q value was 1100 or less or poor sintering occurred. On the other hand, in Table 2, No. 30-32, 34
~ 36, 38 ~ 40, 42 ~ 44, 46 ~ 48, 50 ~
52, 54 to 56, 58 to 60, and 62 to 64 can be fired at a lower temperature than when no iron group metal or the like is added, and it can be seen that the bulk density is higher and the Q value is higher even when fired at a lower temperature.

Further, according to Table 4, even when a plurality of kinds of iron group metals and the like are added, firing can be performed at a lower temperature than when no iron group metals and the like are added.
It turns out that the value has a high characteristic of 3600 or more.

[0034]

As described in detail above, a predetermined molar ratio of Ca
The main component consisting of O, MgO, and WO ₃ includes iron group metals and Zn.
By including the divalent metal of the above, the firing temperature can be lowered by about 100 ° C. as compared with the case where the iron group metal or the divalent metal of Zn is not added, and the firing temperature is not added by the iron group metal or the divalent metal of Zn. Even when the temperature is lowered by about 100 ° C., the Q value is equal to or higher than that when fired at a high temperature, and the porcelain density can be equal to or higher than that of the conventional case, and high strength can be achieved. Can be. 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 (2)

[Claims] [Claim 1] contains at least Ca, Mg and W as the metal element, the molar ratio composition formula a xCaO · y of the metal element oxide [(1-a) MgO · aAO] · zWO ₃ (A iron A, x, y, and z are 0.01 ≦ a ≦ 0.80 0.40 ≦ x ≦ 0.55 0.15 ≦ y ≦ 0. 30 0.20 ≦ z ≦ 0.30 x + y + z = 1. 2. A compound of the general formula Ca [(Mg _1-a A _a )
_2. The dielectric ceramic composition according to claim 1, wherein a main crystal is a perovskite crystal (0.01 ≦ a ≦ 0.80) represented by _1/2 W _1/2 ] O ₃ .