Sumitomo Metal Mining Company, Ltd.

Takehiro Hyuga

Kazutoshi Matsumoto

Tetsuya Mukai

Tetsuro Nakamura

Hiroshi Ichimura

Koh Takada

A high frequency circuit elemental device comprising a casing and a dielectric ceramic mounted in said casing, such as oscillators, said dielectric ceramic being capable of undergoing order-disorder structural transformation, whereby the temperature coefficient of the resonant frequency of said elemental device can be compensated by heat-treatment of the dielectric ceramic.

Resonant frequency-temperature characteristics compensable high

Dielectric ceramic and process of producing the same. A dielectric ceramic essentially consisting of a compound having a disordered perovskite-type complex crystal structure and having a composition represented by the general formula (I):

Dielectric ceramic and process for producing the same

A process for producing a dielectric ceramic comprising a firing step comprises the substeps of heating a calcined product rapidly up to a temperature of from 1,500.degree. to 1,700.degree. C. and thereafter sintering the product at the temperature, and heating the product thus heat-treated through said first heat-treating substep at about 1,200.degree. C. to 1,600.degree. C. for not less than 10 minutes. It is possible to prepare a dielectric ceramic with a desired temperature properties of the resonant frequency.

Process for producing a dielectric ceramic

A dielectric ceramic composition possessing a high dielectric constant and a high unloaded Q and exhibiting stable electric properties even in the high frequency range of 10 GHz contains BaO, ZnO, MgO, NiO, ZrO.sub.2 and Ta.sub.2 O.sub.5 in amounts of not less than 59.0 mol % and not more than 66.0 mol % of BaO, less than 10 mol % of ZnO, less than 10 mol % of MgO, less than 10 mol % of NiO, less than 10 mol % of ZrO.sub.2, and not less than 19.0 mol % and less than 24 mol % of Ta.sub.2 O.sub.5.

Electric ceramic composition

A dielectric ceramic which has a composition represented by the following general formula (I) and having a substantially perovskite crystal structure:

Dielectric ceramics

A dielectric ceramics comprises a complex oxide having a perovskite-type crystal structure, the complex oxide substantially having the composition represented by the following general formula (I)

Dielectric ceramic

A dielectric ceramics possessing a high level of unloaded Q and low loss at high frequency beneficial for communications at high frequency is produced by a method which comprises heating a green compact of a composition represented by the general formula: xBaO.yMgO.zTa.sub.2 O.sub.5 (wherein x, y, and z satisfy 0.5.ltoreq.x.ltoreq.0.7, 0.15.ltoreq.y.ltoreq.0.25, 0.15.ltoreq.z.ltoreq.0.25, and x+y+z=1) to a temperature in the range of 1,500.degree. to 1,700.degree. C. at a temperature increasing rate of 100.degree. to 1,600.degree. C./minute and subsequently retaining the green compact at the temperature for not less than 30 minutes.

Method for manufacture of high-frequency dielectric ceramics

Dielectric ceramics represented by the following general formula and substantially having the K.sub.2 NiF.sub.4 type crystal structure,

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Ichikawa, Japan

Takehiro Hyuga