Kyocera Corporation

Hideki Uchimura

Shoji Kohsaka

Masaki Terazono

Kenichi Tajima

Koichi Tanaka

Shigenobu Nakamura

Tomohiro Kawamoto

Takehiro Oda

Masahito Nakanishi

Sentaro Yamamoto

Hirotaka Tsuyoshi

Susumu Ono

Kazunori Koga

Kazumi Osamura

Shoji Kousaka

Akira Saito

Hiroshi Maruyama

Kouichi Tanaka

Masahiro Satoh

Tomohiro Iwaida

Laminated piezoelectric actuator

A dielectric material having a low dielectric loss factor for high-frequency use, which comprises a sintered product of silicon nitride chiefly composed of silicon nitride and containing at least oxygen as an impurity component or oxygen as an impurity component and a compound of an element of the Group 3a of periodic table, wherein said sintered product contains aluminum in an amount which is not larger than 2% by weight reckoned as an oxide thereof having relative densities of not smaller than 97% and has a dielectric loss factor at 10 GHz ofnot larger than 5.times.10.sup.-4. The dielectric material has excellent mechanical properties such as large strength and excellent chemical stability, features small dielectric loss factor in high-frequency regions, and is suited for use as a material for high-frequency oscillators, antennas, filters and electronic circuit boards. In particular, those dielectric materials are suited for use as window materials for introducing high frequencies in a high-frequency plasma-generating CVD apparatus, a microwave wave output unit and an oscillator.

Dielectric material having a low dielectric loss factor for

A sintered product of silicon nitride containing not smaller than 70 mol % of a .beta.-silicon nitride as well as an element of the Group 3a at least including Lu of periodic table and impurity oxygen, wherein when the content of the element of the Group 3a of periodic table and the content of the impurity oxygen are, respectively, expressed being reckoned as the amount of an oxide of the element of the Group 3a of periodic table (RE.sub.2 O.sub.3) and as the amount of SiO.sub.2 of impurity oxygen, their total amount is from 2 to 30 mol %, the molar ratio (SiO.sub.2 /RE.sub.2 O.sub.3) of the amount of the element of the Group 3a of periodic table reckoned as the oxide (RE.sub.2 O.sub.3) thereof to the amount of impurity oxygen reckoned as SiO.sub.2 is from 1.6 to 10, and the intergranular phase of the sintered product chiefly comprises a crystal phase consisting of the element of the Group 3a of periodic table, silicon and oxygen and a process for producing the same. The sintered product has a large strength from room temperature through up to high temperatures and maintains excellent resistance against oxidation even at high temperatures, and exhibits excellent resistance against creeping and excellent breaking toughness.

Sintered product of silicon nitride

A silicon nitride-silicon carbide composite sintered material which comprises 100 parts by weight of a silicon nitride component containing 92 to 99.5 mol % of silicon nitride including excessive oxygen and 0.5 to 8 mol % of the elements of Group IIIa in the Periodic Table as corresponding oxides thereof and 1 to 100 parts by weight of a silicon carbide component in a dispersed state, wherein the silicon nitride component has an average particle size of 1 .mu.m or less and an average aspect ratio of 2 to 10, and the silicon carbide component has an average particle size of 1 .mu.m or less, moreover, the total amount of Al, Mg, Ca respectively contained in the sintered material as calculated as oxides thereof is 0.5% by weight or less, and a manufacturing method thereof. According to the above-mentioned composite sintered material, it becomes possible to suppress deterioration of strength at 1400.degree. C. and realize excellent creep properties. Therefore, the composite sintered material is applicable not only to structural materials for heat engines such as gas turbines and turbo-rotors but also to other heat resistant materials for various uses.

Silicon nitride-silicon carbide composite sintered material and

Disclosed is a silicon nitride sintered body comprising 70 to 99 mole % of silicon nitride, 0.1 to 5 moles % of a rare earth element oxide and up to 25 moles % of silicon oxide and having a silicon oxide-to-rare earth element oxide molar ratio of from 2 to 25, wherein silicon nitride crystal grains have a fine acicular structure having an average particle major axis of up to 7 .mu.m and an average aspect ratio of at least 3.

Silicon nitride sintered body and process for preparation thereof

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Kokubu, Japan

Hideki Uchimura