Process for production of silicon nitride material

Details Process for production of silicon nitride material Process for production of silicon nitride material

1999-05-28

2000-08-08

Derrington, James

Plastic and nonmetallic article shaping or treating: processes

Outside of mold sintering or vitrifying of shaped inorganic...

Including plural heating steps

676683, C04B 35587

Patent

active

06099794&

ABSTRACT:
A silicon nitride sintered material includes silicon nitride and rare earth element compounds. Y and Yb are contained as the rare earth elements in a total amount of 5-7 mole % in terms of oxides, Yb/Y is 4/6 to 9/1 in terms of molar ratio of oxides, and the crystal phases of grain boundary contain a H phase and a J phase with the proportion of the H phase being larger than that of the J phase. A process for producing a silicon nitride sintered material includes the steps of mixing a Si.sub.3 N.sub.4 powder with Y.sub.2 O.sub.3 and Yb.sub.2 O.sub.3 both as a sintering aid, the total amount of Y.sub.2 O.sub.3 and Yb.sub.2 O.sub.3 being 5-7 mole % and the molar ratio of Yb.sub.2 O.sub.3 /Y.sub.2 O.sub.3 being 4/6 to 9/1, molding the resulting mixture, sintering the molded material in a nitrogen atmosphere at 1,850-1,950.degree. C., and heat-treating the sintered material in air at 1,000-1,500.degree. C. for 0.5-10 hours. The silicon nitride sintered material has, in a small or large thickness, oxidation resistance and strength at low temperatures while retaining high strength at high temperatures.

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M. Isomura et al. "High-strength silicon nitride ceramics and their manufacture", Chemical Abstracts, vol. 118, No. 8, Abstract No. 65444, Feb. 22, 1993.

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