JPS6158424B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a dielectric ceramic composition, in particular a dielectric composed of barium oxide (BaO), magnesium oxide (MgO), niobium oxide (Nb ₂ O ₅ ) and titanium oxide (TiO ₂ ). This relates to porcelain for resonators. 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, there has been an active effort to miniaturize these circuits. progress is being made. Until now, cavity resonators and antennas 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 in which the wavelength itself is shortened by using dielectric ceramics with a high dielectric constant. TiO ₂ is a suitable material for such applications.
For example, TiO ₂ -ZrO ₂
―SnO ₂ system, CaTiO ₃ ―MgTiO ₃ ―La ₂ O ₃ ―2TiO ₂
system, recently Ba(Zn _1/3 Ta _2/3 )O ₃ -Ba
Dielectric ceramics such as (Zn _1/3 Nb _2/3 ) O ₃ type ceramics are known. However, when making a dielectric resonator using these materials, the relative permittivity is as low as about 30, so for example, an X-band dielectric resonator with a resonant frequency of about 11 GHz has a relative permittivity of ε _r =30. If this material is used, it will be a small unit with a diameter of 5.6 mm and a thickness of 2.2 mm, but the frequency will be lowered to about 2 GHz.
When used in the UHF band, the material with the same dielectric constant 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 ε _r of the material used here could be increased to about 80, the size could be reduced to about 18.8 mm in diameter and 7.5 mm in thickness, but conventional materials cannot satisfy these requirements. I couldn't do that. Purpose of the Invention The present invention has been made to improve the above-mentioned drawbacks, and is aimed at improving the relative dielectric constant (ε _r ) and the unloaded Q (Q _u ).
The object of the present invention is to provide a dielectric ceramic that has a stable temperature coefficient (τ _f ) of the resonant frequency and that can vary the temperature coefficient over a wide range depending on the application. Structure of the Invention The dielectric ceramic composition according to the present invention comprises Ba
(Mg _1/3 Nb _2/3 ) In the composition represented by _1-x TixO ₃ , it is a composition in the range of 0<x≦0.5 (mole fraction), and the above objective can be achieved with such a composition. It is something. DESCRIPTION OF EXAMPLES Hereinafter, the details will be explained by giving examples of the present invention and comparative examples. Starting materials include chemically highly purified BaCO ₃ ,
MgO, Nb ₂ O ₅ , and TiO ₂ were weighed to give a predetermined composition and wet mixed with pure water in a rubber-lined ball mill equipped with an agate ball. After taking out this mixture from the ball mill and drying it,
It was calcined in air at a temperature of 1100°C for 2 hours.
The calcined product was wet-pulverized in the ball mill with pure water. After dehydrating and drying the crushed slurry, 8% by weight of a polyvinyl alcohol solution with a concentration of 6% was added to the powder as a binder to make it homogeneous.
The grains were sized through a mesh sieve. The sized powder was molded into a disk with a diameter of 20 mm and a thickness of about 8 mm using a mold and a hydraulic press at a molding pressure of 800 kg/cm ² . The molded body is placed in a high-purity alumina pot and kept in the air at a temperature within the range of 1200 to 1600℃ for 2 hours depending on the composition and fired to produce dielectric porcelain with the composition shown in the table below. Obtained. Using this ceramic element, the resonant frequency and no-load Q were measured using the dielectric resonator method.
The relative dielectric constant was determined. 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】

[Table] *marks indicate comparative examples outside the scope of the present invention.
**marks indicate values at a frequency of 1MHz.
As is clear from the table, the dielectric ceramic within the scope of the present invention can have a large dielectric constant in the microwave frequency band, exhibits a large no-load Q value, and exhibits stable temperature 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 shows an improvement in the dielectric constant, but the resonance in the micro frequency band becomes weak. Since the drop in the no-load Q is noticeable, it is excluded from the scope of the present invention. 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,
By changing the composition of the material, the temperature coefficient of the desired resonant frequency can be selected, so when a dielectric resonator is assembled, it is possible to create a temperature compensation effect that eliminates the influence of the surrounding metal plates on the temperature characteristics. It can be made to stand. 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. This is a large one.

Claims (1)

[Claims] 1 Consists of barium oxide, magnesium oxide, niobium oxide, and titanium oxide, and its composition formula is Ba.
(Mg _1/3 Nb _2/3 ) _1-x TixO ₃ A dielectric ceramic composition characterized in that its component composition is in the range of 0<x≦0.5 in molar fraction.