JPH0118523B2 - - 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 porcelain, for example,
ZnO ₂ −SnO ₂ −TiO ₂ material, Ba ₂ Ti ₉ O ₂₀ , (Ba,
These include Sr) (Zr, Ti) O ₃ -based materials and Ba (Zn, Ta) O ₃ -based materials. It has been reported that these various materials have dielectric constants (ε _r of 20 to 40, Q of 4000 to 8000, and temperature coefficients of resonance frequency (τ _f ) of around Oppm/℃ in the microwave band. Among these, Ba (Zn, Ta) O ₃ type material is a suitable conventional example of this invention. This Ba (Zn, Ta) O ₃ type material is described in Japanese Patent Laid-Open No. 53-35454. A detailed explanation has been given.According to the detailed explanation, dielectric porcelain is obtained by firing in air at a temperature range of 1360-1460℃ for 2 hours.
Assuming that the size is 5 mm in diameter and 2 mm in thickness, we can calculate the resonant frequency (approximately 11 GHz) and the dielectric constant (ε _r ) from the diameter, and also determine the unloaded Q using the band reflection method.
When the temperature coefficient (τ _f ) of the resonant frequency was measured in the temperature range of °C, it was found that ε _r was 25 to 30, Q was 3520 to 3720, and τ _f was 5 to 20 ppm/°C. 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 , but 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 that it will be shown. The reason for the change in Q value due to firing time is as follows. First, Ba(Zn _1/3 Nb _2/3 )O ₃ is “Ordering in
Compounds of the A(B _{0.33′Ta 0.67} )O ₃ Type”,
F. Galasso and J. Pyle, Inorganic Chemistry,
As introduced in Vol 2, No. 3, P482-484, it has a cubic complex perovskite structure consisting of ABO ₃ , and its crystal structure is
The regular arrangement of Zn and Ta forms a hexagonal superlattice. FIG. 1 shows the crystal structure of Ba(Zn _1/3 Ta _2/3 ) O ₃ , in which Zn1 and Ta2 at position B are ordered in a ratio of 1:2. Note that 3 represents Ba and 4 represents O. However, it is said that this ordered structure changes greatly depending on the firing conditions. That is, the second
As shown in the figure, the firing temperature was 1350℃, and the
When we examined the dependence of the (422) and (226) reflection patterns on the firing time in line diffraction, we found that the formation of an ordered arrangement of Zn and Ta was insufficient with a firing time of about 2 hours, whereas with a firing time of 120 hours explains that Zn and Ta are sufficiently ordered and that this 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. Recently, however, the frequency range used has become higher, and materials with higher Q values are required. In view of the above points, the inventors of the present invention have conducted extensive research, and as a result, the present inventors have found that the present invention has a high dielectric constant in the high frequency range and a high QQ without requiring a long firing time.
They have discovered a high-frequency dielectric ceramic composition that has a high value and can obtain any temperature coefficient of resonance frequency around 0 ppm/°C. That is, the gist of this invention is that BaO,
It consists of ZrO ₂ , ZnO, and Ta ₂ O ₅ , which is expressed by the general formula Ba
(Zr _x Zn _y Ta _z )O When expressed as _7/2-x/2-3y/2 , x,
y, z are 0.02≦x≦0.13, 0.28≦y≦0.33, 0.59≦
In the range of z≦0.65 (however, x+y+z=1),
A dielectric ceramic composition for high frequency, which has as a main component 70 atomic % or less of Zn substituted with one or both of Ni and Co, and further contains 0.1 to 1.0 mol % of MnO ₂ . be. Here, in Ba(Zr _x Zn _y Ta _z ) O _7/2-x/2-3y/2 ,
The reason why x, y, and z are each limited to the above-mentioned ranges is as follows. In other words, the reason why we set x in the range of 0.02 to 0.13 is because x is
If it is less than 0.02, Q will decrease, or 0.13
This is because if the temperature coefficient exceeds , the temperature coefficient of the resonance frequency becomes large on the positive side. The reason why y is set to 0.28 to 0.33 is that it is less than 0.28,
If it exceeds 0.33, sintering becomes difficult. The reason why z is set to 0.59 to 0.65 is that if z is less than 0.59 and exceeds 0.65, sintering becomes difficult. Also, Zn in Ba(Zr _x Zn _y Ta _z )O _7/2-x/2-3y/2 is replaced by Ni,
When replacing one or both of Co, the substitution amount is set to 70 atomic % or less because if it exceeds 70 atomic %, the temperature coefficient of the resonance frequency becomes too large on the negative side. Next, the amount of MnO ₂ to be added to the above main components is specified as 0.1 to 1.0 mol%, because if it is less than 0.1 mol%, it will not have the effect of increasing the Q value, and if it is more than 1.0 mol%, the dielectric constant and Q This is because the value decreases. This invention will be explained in detail below with reference to Examples. Examples Highly purified BaCO ₃ , ZrO ₂ , ZnO,
Ta ₂ O ₅ , NiO, Co ₂ O ₃ , and MnO ₂ were weighed to obtain porcelain having the composition ratio shown in Table 1, and the weighed raw materials were placed in a rubber-lined ball mill with agate stone,
It was added together with pure water and wet-mixed for 2 hours. Next, this mixture was dehydrated and dried, then calcined at 1200℃ for 2 hours, and the calcined product was placed in a ball mill with agate stone,
It was added together with pure water and an organic binder and wet-pulverized for 2 hours. Next, after drying this pulverized material, it was granulated through a 50-mesh mesh, and the resulting powder was powdered at 2000 kg/cm ²
It was molded into a disk with dimensions of 12 mmφ x 6 mmt under a pressure of . Further, this disk was fired at 1450°C for 4 hours to obtain a porcelain sample. Regarding the obtained ceramic sample, the dielectric constant (ε _r )Q and the temperature coefficient of resonance frequency (τ _f ) at a frequency of 7 GHz were measured by the dielectric resonator method, and the results are shown in Table 1. Note that the * mark in Table 1 is outside the scope of this invention, and all others are within the scope of this invention.

【table】

[Table] In Table 1, sample numbers 1, 49, 52, and 55 are
It consists of a composition in which a part of Zn is not replaced with either or both of Ni and Co, and is outside the scope of this invention. In addition, sample number 8 has a Ni and Co substitution amount of 70 atomic%.
This is an example in which the resonant frequency (τ _f ) tends to increase on the negative side, and is therefore excluded from the scope of the present invention. Sample numbers 1, 2, 3, 10, 16, 17, 23, 29,
Examples 30, 36, 42, 43, 49, 52, and 55 do not contain MnO ₂ and are outside the scope of this invention. Next, sample numbers 9, 15, 22, 28, 35, 41, 48 are
This is an example in which 1.0 mol % or more of MnO ₂ is added, and this is excluded from the scope of the present invention because the dielectric constant and Q value decrease. Furthermore, sample numbers 49 to 57 are Ba (Zr _x Zn _y Ta _z )
The x, y, and z values of O _7/2-x/2-3y/2 are outside the scope of this invention, and sintering is difficult or the properties are degraded. Characteristics are not shown for sample numbers 49, 50, 52, and 53, but this is because sufficiently sintered porcelain could not be obtained and it was impossible to measure the characteristics. As detailed above, according to the present invention, it is possible to obtain a dielectric ceramic composition for high frequencies which has a high dielectric constant and also exhibits a high Q value which could not be obtained conventionally by adding MnO ₂ . In addition, part of Zn is Ni,
The temperature coefficient of the resonant frequency can also be adjusted by appropriately selecting the amount of Co to be substituted with either or both of them.
Any value can be obtained on the positive and negative sides around 0 ppm/℃. Therefore, according to the present invention, it is possible to provide a high frequency dielectric ceramic composition useful for applications such as dielectric resonators, dielectric adjustment rods, and dielectric substrates for MIC.

[Brief explanation of drawings]

Figure 1 shows the crystal structure of Ba(Zn _1/3 Ta _2/3 ) O ₃ , and Figure 2 shows Ba(Zn _1/3 Ta _2/3 ) O ₃ in relation to firing time. It is an X-ray diffraction diagram.

Claims (1)

[Claims] 1 Consists of BaO, ZrO ₂ , ZnO, 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, z is 0.02≦x≦0.13, 0.28≦y≦
0.33, 0.59≦z≦0.65 (however, x+y+z=1), and the main component is one in which 70 atom % or less of Zn is substituted with either or both of Ni and Co, and MnO ₂ A high frequency dielectric ceramic composition containing 0.1 to 1.0 mol% of.