Tosoh Corporation

Honda Giken Kogyo Kabushiki Kaisha

Toshiyuki Mori

Hiroshi Yamamura

Toshihiko Arakawa

Takashi Mitamura

Hidehiko Kobayashi

Yoshitaka Kubota

Hideto Kuramochi

Yasunobu Kawakami

Kagehisa Hamazaki

Naoki Kosugi

Yoshihiro Matsumoto

Hirokuni Hoshino

A defective fluorite structure type solid electrolyte of the following formula (1):

Fluorite structure type ceria type solid electrolyte

A method for preparing zircon powder, which comprises mixing (1) silica sol and (2) an aqueous zirconium oxychloride solution having a concentration which would be from 0.1 to 2 mols/l after mixed with the silica sol, in a SiO.sub.2 /ZrO.sub.2 molar ratio of from 0.95 to 1.10, heating the mixture to hydrolyze the zirconium oxychloride, followed by dehydration treatment to obtain a powder, heating the powder from room temperature to a calcination temperature over a period of from 0.7 to 30 hours and calcining the powder at a temperature of from 1,200.degree. to 1,400.degree. C. for a period of time satisfying the relation of:

Method for preparing zircon powder

A pollucite powder consisting essentially of a pollucite phase and having an Al.sub.2 O.sub.3 /SiO.sub.2 molar ratio of from 0.21 to 0.25 and a Cs.sub.2 O/SiO.sub.2 molar ratio of from 0.19 to 0.22.

Pollucite crystalline powders with low thermal expansion coefficients

A silicon nitride sintered body having a composition of 1.5-3.0 weight % of Y.sub.2 O.sub.3, 0.1-1.0 weight % of Al.sub.2 O.sub.3 and balance substantially Si.sub.3 N.sub.4, a weight ratio of Y.sub.2 O.sub.3 /Al.sub.2 O.sub.3 being 2.5 or more, which has a density of 3.0 g/cm.sup.3 or more and has a structure in which the minor axes of grains are substantially 6 .mu.m or less. This silicon nitride sintered body is produced by preparing a powder mixture containing Y.sub.2 O.sub.3 powder, Al.sub.2 O.sub.3 powder and silicon nitride powder in the above proportions, the silicon nitride powder having an oxygen content of 1.2 weight % or less, a specific surface area of 9-11 m.sup.2 /g and a metal impurity content of 200 ppm or less; and sintering the powder mixture at a temperature of 1900.degree.-2100.degree. C. and a pressure of 5 kg/cm.sup.2 G or more in a nitrogen atmosphere.

Silicon nitride sintered body having excellent high-temperature strength

A preparation method for zircon powder, which comprises heating a feed powder mixture comprising:

Preparation method for zircon powder

A silicon nitride sintered body comprised of 1.5 to 3.0% by weight of Y.sub.2 O.sub.3, 0.1 to 1.0% by weight of Al.sub.2 O.sub.3 and 96 to 98.4% by weight of Si.sub.3 N.sub.4 wherein the Y.sub.2 O.sub.3 /Al.sub.2 O.sub.3 weight ratio is at least 2.5, and having a density of at least 3.0 g/cm.sup.3, exhibits a high oxidation resistance and a high strength at a high temperature. This silicon nitride sintered body is prepared by sintering a powdery mixture consisting essentially of 1.5 to 3.0% by weight of Y.sub.2 O.sub.3 powder, 0.1 to 1.0% by weight of Al.sub.2 O.sub.3 powder, and 96 to 98.4% by weight of Si.sub.3 N.sub.4 powder, the Y.sub.2 O.sub.3 /Al.sub.2 O.sub.3 weight ratio being at least 2.5, the oxygen content in the Si.sub.3 N.sub.4 powder being less than 2.0% by weight and the total metallic impurity content in the Si.sub.3 N.sub.4 being less than 200 ppm, at a temperature of 1,850.degree. to 2,000.degree. C. in a non-oxidizing atmosphere.

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Tsuchiura, Japan

Toshiyuki Mori