JPS6256606B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is a dielectric ceramic composition, in particular composed of barium oxide (BaO), nickel oxide (NiO), tantalum oxide (Ta ₂ O ₅ ) and titanium oxide (TiO ₂ ), which has a dielectric It has a large coefficient (ε _r ), a large unloaded Q (Q _u ) when used as a dielectric resonator in the microwave frequency band, and a stable temperature coefficient (τ _f ) of the resonant frequency, making it suitable for various applications. This invention relates to dielectric ceramics whose temperature coefficients can be varied over a wide range depending on the situation. Conventional configuration and its problems In recent years, with the advancement of high-frequency circuit technology that handles microwaves and millimeter waves (hereinafter collectively referred to as microwaves) with wavelengths of several centimeters or less, it has become necessary to miniaturize this circuit. is being actively promoted. Until now, cavity resonators, antennas, etc. have been used in these high-frequency circuits, but their size is comparable to the wavelength of microwaves, which has been an obstacle to miniaturization. In order to solve this problem, a method has been taken to shorten the wavelength itself by using dielectric ceramics with a high dielectric constant. _TiO2 -based materials are often used as materials suitable for such applications, such as
TiO ₂ −ZrO ₂ −SnO ₂ system, CaTiO ₃ −MgTiO ₃ −
La ₂ O ₃ −2TiO ₂ series, recently Ba (Zn _1/3 Ta _2/3 )
Dielectric ceramics such as O ₃ −Ba (Zn _1/3 Nb _2/3 ) O ₃ series are known. However, when making a dielectric resonator using these materials, the dielectric constant is as low as about 30, so for example, for an X-band dielectric resonator with a resonance frequency of about 11 GHz, a material with ε _r = 30 is used. When used, it becomes a small unit with a diameter of 5.6 mm and a thickness of 2.2 mm, but the frequency is lowered to about 2 GHz.
When used in the UHF band, the same material with ε _r = 30 becomes significantly larger, with a diameter of 30.7 mm and a thickness of about 12.3 mm. If the dielectric constant of the material used here could be increased to about 80, the size could be reduced to 18.8 mm in diameter and 7.5 mm in thickness, but conventional materials cannot satisfy these requirements. I couldn't do it. Purpose of the Invention The present invention has been made to improve the above-mentioned drawbacks, and has improved relative dielectric constant and no-load Q, and has a stable temperature coefficient of resonance frequency. The purpose is to provide dielectric ceramics that can be varied over a wide range. Structure of the Invention As a result of various studies on materials that meet the above requirements, the inventors found that Ba(Ni _1/3 Ta _2/3 ) _1-x Ti _x O ₃
It has been found that, in the composition represented by the following, a composition in the range of 0<x≦0.5 (mole fraction) becomes an excellent dielectric ceramic for high frequency use. Description of Examples The starting materials are chemically highly purified BaCO ₃ , NiO,
Ta ₂ O ₅ and TiO ₂ were weighed to give a predetermined composition, and wet mixed with water in a polyethylene ball mill equipped with an agate ball. This mixture was taken out from the ball mill, dried, and then calcined in air at a temperature of 1100°C for 2 hours. The obtained calcined product was wet milled together with water in the ball mill described above. After filtering and drying the crushed slurry,
The powder was made homogeneous by adding 8% by weight of a polyvinyl alcohol solution with a concentration of b% as a binder, and then passed through a 32-mesh sieve to size the powder. The sized powder is molded at a pressure of 800 using a mold and hydraulic press.
The material was molded into a disc with a diameter of 20 mm and a thickness of approximately 8 mm using Kg/cm ² . The molded body was placed in a high-purity alumina pot and kept in the air at a temperature within the range of 1200 to 1550°C for 2 hours depending on the composition and fired to obtain dielectric porcelain with the composition shown in the table. Ta. Using this ceramic element, the resonant frequency, no-load Q, and relative dielectric constant were determined from measurements using the dielectric resonator method. The temperature dependence of the resonance frequency was measured in the range of -30°C to 70°C, and the temperature coefficient τ _f was determined. The resonant frequency was between 2 and 4 GHz. The experimental results are shown in the table. Note that the samples marked with * in the table are comparative examples outside the scope of the present invention, and the other samples are examples within the scope of the present invention.

[Table] As is clear from the table, the dielectric ceramic within the scope of the present invention can have a large relative permittivity in the microwave frequency band, exhibit a large no-load Q value, and maintain a stable temperature. It shows the characteristics. Therefore, the dielectric ceramic of the present invention is useful for stabilizing the temperature dependence of oscillators and resonators, and is particularly suitable for use in the UHF band due to its large dielectric constant, and is a compact and high-performance device. Can make electronic circuit parts. To explain the reason why the composition range of the present invention is limited, porcelain with a composition in which the amount of TiO ₂ (x) exceeds 0.5 mole fraction can be seen to improve the dielectric constant, but the resonance in the micro frequency band becomes weak. This is excluded from the scope of the present invention because the drop in no-load Q is significant. Furthermore, porcelain with x=0 has a small dielectric constant and does not meet the purpose of the present invention, and is therefore excluded from the scope of the present invention. Effects of the Invention The dielectric ceramic composition of the present invention has a large dielectric constant in the microwave frequency band, a large no-load Q, and a stable temperature coefficient of the resonant frequency. Useful for stabilizing dependencies. Additionally, due to its high dielectric constant, it is suitable for use in the UHF band, and can be used to create small, high-performance electronic circuit components. moreover,
Since the desired τ _f can be selected by changing the composition of the material, a temperature compensation effect can be provided to eliminate the influence of surrounding metal plates on the temperature characteristics when the dielectric resonator is assembled. Can be done. In addition, the dielectric ceramic composition of the present invention can provide a material useful not only for dielectric resonators but also for microwave substrates, dielectric adjustment rods, etc., and has industrial utility value. It's big.

Claims (1)

[Claims] 1 It consists of barium oxide, nickel oxide, tantalum oxide, and titanium oxide, and its composition formula is Ba.
(Ni _1/3 Ta _2/3 ) _1-x Ti _x O ₃ A dielectric ceramic composition characterized in that its component composition is within the range of 0<x≦0.5 in terms of molar fraction. .