JPS6256099B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a dielectric ceramic composition for high frequency use. In high-frequency regions such as microwaves and millimeter waves, dielectric ceramics are widely used in dielectric resonators and dielectric substrates for MICs. Conventionally, as this type of dielectric ceramic, there are various types as shown below. For example, ZrO ₂ −SnO ₂ −TiO ₂ based materials,
Ba ₂ Ti ₉ O ₂₀ , (Ba, Sr) (Zr, Ti) O ₃ material, Ba
(Zn, Ta) _O3 -based materials, etc. It has been reported that these various materials have a dielectric constant (εr) of 20 to 40, a Q of 4000 to 8000, and a temperature coefficient of resonance frequency (τ) of around 0 ppm/°C in the microwave band. There is. Among these, Ba(Zn, Ta)O ₃ material is a suitable conventional example of the present invention. This Ba(Zn, Ta)O ₃ based material is described in detail in Japanese Patent Application Laid-Open No. 53-35454. According to the detailed description, dielectric porcelain is obtained by firing in the air for 2 hours at a temperature range of 1360℃~1460℃, and its size is 5 mm in diameter.
mm, thickness 2 mm, resonance frequency (approximately
11GHz), the dielectric constant (εr) from the diameter, the unloaded Q using the band reflection method, and the temperature coefficient (τ) of the resonant frequency in the temperature range of -30℃ to +70℃. , for Q
3520 to 3730, and τ exhibits characteristics of 5 to 20. Recently, the following reports have been made regarding this Ba(Zn, Ta)O ₃ based material. In other words, dielectric porcelain was fired using the normal firing method for Ba(Zn〓Ta〓)O ₃ , and the firing conditions were a maximum temperature of 1650°C and a firing time of 2 to 300°C.
The results are considered over a 120 hour period. According to this, porcelain fired for 120 hours showed a Q value of 14,000 when measured in a waveguide, and when porcelain fired for 2 hours was measured using the same method (12GHz), it showed a Q value of 10,000 to 11,000. It is said to be shown. The reason for the change in Q value due to firing time is as follows. First, Ba(Zn〓Nb〓)O ₃ is “Ordering in
Compounds of the A (B' _{0. 33} Ta _{0. 67} )
O ₃ Type″, F.Galasso and J.Pyle, Inorganic
As introduced in Chemistry, vol.2, No.3, p.482−484, cubic crystals consisting of ABO ₃
It has a complex perovskite structure, and its crystal structure is a hexagonal superlattice formed by regularly arranging Zn and Ta. Figure 1 shows the crystal structure of Ba(Zn〓Ta〓)O ₃ , in which Zn and Ta at the B position are ordered in a ratio of 1:2. In the figure, 〓 is barium (BARIUM), 〇 is oxygen (OXYGEN), 〓 is zinc (ZINC), and 〓 is tantalum (TANTALUM). However, this ordered structure is said to vary greatly depending on the firing conditions. That is,
As shown in Figure 2, we set the firing temperature to 1350°C and examined the dependence of (422) and (226) reflection patterns on firing time in X-ray diffraction of porcelain. It is explained that the formation of an ordered arrangement of Ta is insufficient, while Zn and Ta are sufficiently ordered after a firing time of 120 hours, which leads to an improvement in the Q value. However, in order to obtain porcelain with a high Q value,
Maintaining the firing time for as long as 120 hours is a major obstacle to improving productivity and leads to increased costs. Furthermore, operating the kiln for as long as 120 hours at high temperatures shortens the life of the kiln, which also increases the cost of the product. As a result of intensive research, the inventors discovered that a high-frequency dielectric ceramic composition with a high Q value can be obtained without requiring a long firing time. The porcelain composition consists of BaO, ZrO ₂ , ZnO, Ta ₂ O ₅ , which has the general formula Ba(Zr _x Zn _y Ta _z )O _7/2-x
When expressed as _/2-3y/2 , x, y, and z are each in the following range. 0.02≦x≦0.13 0.28≦y≦0.33 0.59≦z≦0.65 (However, x+y+z=1) For such a porcelain composition, each of the raw materials is mixed, calcined, and further shaped to produce porcelain under firing conditions for about 4 hours. A sample was prepared, and the dielectric constant (ε), Q, and temperature coefficient of resonance frequency (τ
) was measured and the results are shown in Table 1. (Patent Application No. 143294/1982) Here, the temperature coefficient (τ) of the resonant frequency is +25
Measurements were made in the temperature range from °C to +85 °C. Note that the temperature coefficient (τ) of the resonant frequency and the temperature coefficient of the dielectric constant are connected by the following equation. τ=−1/2τ〓−α τ〓: Temperature coefficient of permittivity α: Linear expansion coefficient of ceramic sample

[Table] On the other hand, the conventional composition Ba(Zn〓Ta〓)O ₃
Samples were prepared in the same manner as above, and their electrical properties were measured, with the results shown in Table 2.

[Table] Ba (Zn〓Ta〓) having the properties shown in Table 2
O ₃ has the best Q value among the Ba(ZnTa)O ₃ series, but according to the composition shown in Table 1, it has the highest Q value.
One with a Q value of 15,000 has been obtained, and Ba
Compared to (Zn〓Ta〓)O ₃ , Ba(Zr _x Zn _y Ta _z )O _{7
/2-x/2-3y/2} type products have been obtained which have properties superior to those of the /2-x/2-3y/2 series. Figure 3 shows the electrical properties of a solid solution of Ba(Zn〓Ta〓)O ₃ and BaZrO ₃ created in order to clarify the effect of ZrO ₂ inclusion. According to FIG. 3, it can be seen that a high Q value is obtained when Zr is in the range of 0.02 to 0.13. Also, Figure 4 a and b are Ba(Zn〓Ta〓)O ₃ and Ba
(Zr ₀ . ₀₄ Zn ₀ . ₃₂ Ta ₀ . ₆₄ ) O ₃ X-ray diffraction diagram. In FIG. 4a, the peak at 17.7° observed in Ba(Zn〓Ta〓)O ₃ is a diffraction line due to the (100) plane of the hexagonal crystal, indicating that a superlattice is formed. In contrast, Ba shown in Figure 4b
According to (Zr ₀ . ₀₄ Zn ₀ . ₃₂ Ta ₀ . ₆₄ ) O ₃ , the hexagonal diffraction line shown in Figure 4a has disappeared, and it has a simple cubic perovskite structure. I know that there is. In addition, in Figure 4a, 1 is hexagonal.
(100) face of , 2 is (100) of cubic crystal (Cubic)
Face, 3 is the (002) face of hexagonal crystal, 4
is the K line, and 5 is the (110) plane of the cubic crystal. In FIG. 4b, 1 is the (100) plane of the cubic crystal, 2 is the K line, and 3 is the (100) plane of the cubic crystal. Furthermore, Fig. 5 a and b are respectively Ba(Zn〓Ta
〓) This shows the diffraction lines of K〓 ₁ and K〓 ₂ due to the cubic crystal (321) plane of O ₃ and Ba (Zr ₀ . ₀₄ Zn ₀ . ₃₂ Ta ₀ . ₆₄ ) O ₃ . As is clear from comparing Figures 5a and 5b, according to the composition of Ba(Zr ₀ . ₀₄ Zn ₀ . ₃₂ Ta ₀ . ₆₄ ) O ₃ , separation of K〓 ₁ and K〓 ₂ is possible. It is clear that, despite the same firing conditions, the inclusion of Zr has the effect of promoting the degree of sintering. In Fig. 5a, 1 is the (321) plane of the cubic crystal, which is the K〓 ₁ line, and 2 is the K〓 ₂ line. In Fig. 5b, 1 is the (320) plane of the cubic crystal, which is the K〓 ₁ line, and 2 is the K〓 ₂ line. In this way Ba(Zr _x Zn _y Ta _z ) O _7/2-x/2-3y/2
The crystal structure of the composition is a simple perovskite-type cubic crystal, which is distinguished from Ba(Zn〓Ta〓)O ₃ , which has a superlattice crystal structure. Moreover, the composition consisting of Ba(Zr _x Zn _y Ta _z )O _y/2-x/2-3/2 has a property of having a high Q value under normal firing conditions, and Ba(Zn〓Ta〓) It has the advantage that 120 hours of calcination is not required to obtain a high Q value like O ₃ . However, Ba(Zr _x Zn _y Ta _z ) O _7/2-x/2-3y/2
The temperature coefficient (τ) of the resonant frequency of the composition consisting of
-1 to 16ppm/℃ if the composition ratio is selected
Although it is possible to control the positive side, it is rather difficult to control the negative side. Therefore, it is an object of the present invention to provide a dielectric ceramic composition for high frequencies that has a high Q value and can obtain a temperature coefficient of an arbitrary value around 0 ppm/°C as a temperature coefficient of resonance frequency. . In other words, the gist of this invention is:
It consists of BaO, ZrO ₂ , ZnO, and Ta ₂ O ₅ , and when expressed as the general formula Ba(Zr _x Zn _y Ta _z )O _7/2-x/2-3y/2 , x, y, and z are The dielectric ceramic composition for high frequency is characterized in that each of the compositions is in the following ranges, and 70 atomic % or less of Zn is replaced with either or both of Ni and Co. 0.02≦x≦0.13 0.28≦y≦0.33 0.59≦z≦0.65 (However, x+y+z=1) Here, Ba(Zr _x Zn _y Ta _z )O _7/2-x/2-3y/2 , x, The reason why y and z are limited to the above-mentioned ranges is as follows. In other words, when x is in the range of 0.02 to 0.13,
This is because if x becomes less than 0.02, Q will decrease, and if x exceeds 0.13, the temperature coefficient of the resonance frequency will become large on the positive side. The reason why y is set to 0.28 to 0.33 is because sintering becomes difficult if y is less than 0.28 and exceeds 0.33. The reason why z is set to 0.59 to 065 is that if z is less than 0.59 or exceeds 0.65, sintering becomes difficult. Also, Zn of Ba(Zr _x Zn _y Ta _z )O _7/2-x/2-3y/2
When replacing with either or both of Ni and Co, the amount of substitution is 70 at%.
This is because if it exceeds , the temperature coefficient of the resonance frequency becomes too large on the negative side. Hereinafter, this invention will be explained in detail according to examples. Examples Highly purified BaCO ₃ , ZrO ₂ , ZnO,
Ta ₂ O ₅ , NiO, and CO ₂ O ₃ were weighed to obtain porcelain with the composition ratio shown in Table 1. The weighed raw materials were placed in a rubber-lined ball mill along with agate stone and pure water, and wet-processed for 2 hours. Mixed. After the mixture was dehydrated and dried, it was calcined at 1200° C. for 2 hours, and the calcined product was placed in a ball mill together with agate, pure water, and an organic binder, and wet-pulverized for 2 hours. Next, after drying this pulverized material, it is granulated through a 50-mesh mesh, and the resulting powder is sized to 12mmφ at a pressure of 2000Kg/ ^cm2 .
It was transformed into a disk with dimensions of x6mmt. Furthermore, this disk was fired at 1450°C for 4 hours to obtain a porcelain sample. The dielectric constant (ε), Q, and temperature coefficient of resonance frequency (τ) at a frequency of 7 GHz were measured for the obtained ceramic sample, and the results are shown in Table 3. Items marked with * in Table 3 are outside the scope of this invention.
Everything else is within the scope of this invention.

【table】

【table】

[Table] In Table 3, sample numbers 1, 10, 18, 26,
Nos. 34, 41, and 48 have compositions in which a portion of Zn is not replaced with either or both of Ni and Co. In addition, sample numbers 5, 9, 14, 22, and 33 are Ni, Co
This is an example in which the amount of substitution exceeds 70 atomic %, and the temperature coefficient of the resonance frequency tends to increase on the negative side, so it is excluded from the scope of this invention. Furthermore, sample numbers 56 to 64 are (Zr _x Zn _y Ta _z ) O _7/
The values of x, y, and z of _2-x/2-3y/2 are out of the range, and sintering is difficult and the properties are deteriorated, so it is excluded from the scope of the present invention.
In addition, sample numbers 56 to 61 did not show any characteristics, but this was because sufficiently sintered porcelain could not be obtained.
This is because the characteristics could not be measured. As described above, according to the present invention, it is possible to obtain a material having a high dielectric constant, a high Q value, and also a temperature coefficient of a resonance frequency having arbitrary values on the positive side and the negative side around 0%. In particular, according to this invention, some of the Zn
By substituting Ni and Co, the temperature coefficient of the resonance frequency can be controlled to the negative side. Therefore, according to the present invention, a dielectric resonator,
It is possible to provide a high frequency dielectric ceramic composition useful for applications such as dielectric adjustment rods and dielectric substrates for MIC.

[Brief explanation of the drawing]

Figure 1 shows the crystal structure of Ba(Zn〓Ta〓)O ₃ , Figure 2 shows the X-ray diffraction diagram of Ba(Zn〓Ta〓)O ₃ in relation to firing time, and Figure 3 is Ba
(Zn〓Ta〓)O ₃ -BaZrO ₃ -based solid solution electrical characteristics diagram, Figure 4 a and b are respectively Ba(Zn〓Ta〓)O ₃
X-ray diffraction patterns of Ba(Zr ₀ . ₀₄ Zn ₀ . ₃₂ Ta ₀ . ₆₄ ) O ₃ , Figures 5a and b are Ba(Zn〓Ta〓)O ₃ and Ba, respectively.
(Zr ₀ . ₀₄ Zn ₀ . ₃₂ Ta ₀ . ₆₄ ) This is a diffraction diagram of K〓 ₁ and K〓 ₂ according to the (321) plane of the cubic crystal of O ₃ .

Claims (1)

[Claims] 1 Consisting of BaO, ZrO ₂ , ZnO, Ta ₂ O ₅ and expressed as the general formula Ba(Zr _x Zn _y Ta _z )O _7/2-x/2-3y/2 , x, y, and z are each in the following ranges, and 70 atomic percent or less of Zn is substituted with one or both of Ni and Co. 0.02≦x≦0.13 0.28≦y≦0.33 0.59≦z≦0.65 (However, x+y+z=1)