JPH0567589B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a dielectric ceramic composition for microwave use. (Prior art) In dielectric resonators for microwave circuits, ceramic capacitors for temperature compensation, etc., dielectric ceramic compositions have large relative permittivity (ε _r ) and no-load Q (Qu), and the resonance frequency is low. It is necessary to obtain an arbitrary temperature coefficient whose temperature coefficient (τ _f ) is positive or negative around 0. Conventionally, such dielectric ceramic compositions include:
BaO・TaO ₂ series, MgTiO ₃・CaO series, ZrO ₂・
SnO ₂ and TiO ₂ systems were used. (Problem to be solved by the invention) However, when dielectric resonators and capacitors are manufactured using these dielectric ceramic compositions, when the temperature coefficient (τ _f ) is around 0 pmm/°C, the ratio decreases. The dielectric constant (ε _r ) is as small as 20 to 40, and as a result, it has the disadvantage that it is impossible to miniaturize dielectric resonators and the like. This invention was made in view of the above points, and the relative permittivity (ε _r ) and no-load Q are large even when the temperature coefficient is near 0, and the temperature coefficient (τ _f ) can be varied over a wide range by changing the composition. It is an object of the present invention to provide a dielectric ceramic composition that can (Means for solving the problem) The dielectric ceramic composition of the present invention has (BaO).
_{A dielectric} ceramic composition consisting of _{a (} TiO _{2 ) 2} : 61.8 to 70.3 mol% _{Sm2O3 :} 5 to 19 mol% _Yb2O3 : _0.5 to 12 mol%. (Function) The dielectric ceramic composition described above has a large relative dielectric constant (ε _r ) and no-load Q (Qu) even when the temperature coefficient (τ _f ) of the resonance frequency is around 0, and the The temperature coefficient (τ _f ) changes over a wide range. (Example) Examples of the present invention will be described below. Chemically high-purity barium carbonate (BaCO ₃ ), titanium dioxide (TiO ₂ ), samarium oxide (Sm ₂ O ₃ ) and ytterbium oxide (Yb ₂ O ₃ ) are used as starting materials in Tables 1 and 2. They were mixed at the composition ratio shown and calcined in air at 1060°C for 2 hours.

【table】

[Table] The obtained calcined product was wet-pulverized with pure water in a pot mill, and after dehydration and drying, a binder was added and granulated.
The grains were sized through a mesh sieve. The obtained granulated powder is molded using a mold and a hydraulic press under a molding pressure of 1~
A disc-shaped molded product with a diameter of 16 mm and a thickness of 9 mm was made at 3 ton/cm ² . Then, this molded body was placed in a high-purity alumina pot and fired under firing conditions of 1260°C to 1450°C for 2 hours to obtain a dielectric ceramic composition. The relative dielectric constant (ε _r ) and unloaded Q (Qu) of the obtained porcelain composition were determined by the Hatsuki-Coleman method.
was measured. Also, the temperature coefficient of the resonant frequency (τ _f )
was determined from values in the temperature range of -30°C to 70°C based on the resonance frequency at 20°C according to equation (1) below. The results are shown in Table 2. The resonant frequency in these measurements was 3-5 GHz. τ _f = f(70)-f(-30)/f(20)・1/△T(ppm
/℃)...(1) However, f(20): Resonance frequency at 20℃ f(-30): Resonance frequency at -30℃ f(70): Resonance frequency at 70℃ △T: Measured temperature difference, here 70+30=100°C In Table 2, the sample numbers marked with * are comparative examples outside the scope of the present invention, and the other samples are examples within the scope of the present invention. According to the results in Tables 1 and 2, (BaO)・
(TiO ₂ ) If _x is less than 75 mol% or exceeds 87 mol%, the unloaded Q (Qu) will be small and the relative permittivity (ε _r ) will also be small, making it unsuitable. In addition, if Sm ₂ O ₃ is less than 5 mol% or exceeds 19 mol%, the unloaded Q
(Qu) becomes small and the relative dielectric constant (ε _r ) also becomes small, which is inappropriate. Furthermore, if Yb ₂ O ₃ is less than 0.5 mol % or exceeds 12 mol %, the unloaded Q (Qu) will be small and ε _r will also be small, which is inappropriate. Therefore, from a practical point of view, (BaO)・(TiO ₂ )
_× : 75 to 87 mol% _{, Sm2O3} : 5 to 19 mol%,
Yb ₂ O ₃ : A range of 0.5 to 12 mol% is appropriate. Here, since _x of (BaO)/(TiO ₂ ) x is 3.8 to 4.2, BaO: 15.0 to 18.1 mol%, TiO ₂ : 61.8 to
70.3 mol% _{, Sm2O3} : _5-19 mol%, _Yb2O3 : 0.5
A range of 12 mol % is suitable. Further, according to Table 2, the ceramic composition of the present invention has a large relative dielectric constant (ε _r ) and no-load Q (Qu) when the temperature coefficient (τ _f ) of the resonance frequency is around 0. It is found that the temperature coefficient changes over a wide range due to changes in composition. (Effects of the Invention) As described above, the dielectric ceramic composition of the present invention has a large no-load Q and a large relative dielectric constant even when the temperature coefficient of the resonant frequency is near 0 in the microwave region, and is susceptible to compositional changes in the microwave region. Therefore, the temperature coefficient τ _f can be varied over a wide range. Therefore, it can be used as a dielectric ceramic composition for microwave dielectric resonators, temperature compensation capacitors, etc. to reduce their size, and its industrial value is great.

Claims (1)

[Scope of Claims] 1 A dielectric ceramic composition comprising a (BaO)/(TiO ₂ ) _x -based composition, samarium oxide (Sm ₂ O ₃ ) and ytterbium oxide (Yb ₂ O ₃ ),
A dielectric characterized by having a composition range of BaO: 15.0 to 18.1 mol%, TiO ₂ : 61.8 to 70.3 mol%, Sm ₂ O ₃ : 5 to 19 mol%, Yb ₂ O ₃ : 0.5 to 12 mol%, in terms of oxides. Body porcelain composition.