Claims
- 1. A process for producing a silicon nitride sintered material comprising silicon nitride and rare earth element compounds, which comprises:
- 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 in terms of oxides being 5-7 mole %, based on the total amount in moles of silicon nitride and rare earth elements 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 to form grain boundary crystal phases of an H phase and a J phase with the proportion of the H phase being larger than that of the J phase.
- 2. A process for producing a silicon nitride sintered material according to claim 1, wherein the Si.sub.3 N.sub.4 powder is a mixture of .alpha.-Si.sub.3 N.sub.4 and .beta.-Si.sub.3 N.sub.4, satisfying the following formula:
- .beta./(.alpha.+.beta.).gtoreq.0.1
- (wherein .alpha. is the weight of .alpha.-Si.sub.3 N.sub.4 and .beta. is the weight of .beta.-Si.sub.3 N.sub.4).
Priority Claims (1)
Number |
Date |
Country |
Kind |
8-218809 |
Aug 1996 |
JPX |
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Parent Case Info
This application is a division of application Ser. No. 08/912,516, filed Aug. 18, 1997 now U.S. Pat. No. 5,945,363.
US Referenced Citations (6)
Foreign Referenced Citations (7)
Number |
Date |
Country |
64-61358 |
Mar 1989 |
JPX |
64-61357 |
Mar 1989 |
JPX |
64-56368 |
Mar 1989 |
JPX |
6-227866 |
Aug 1994 |
JPX |
6-219840 |
Aug 1994 |
JPX |
7-29855 B2 |
Apr 1995 |
JPX |
7-33290 B2 |
Apr 1995 |
JPX |
Non-Patent Literature Citations (2)
Entry |
Patent Abstracts of Japan, Publication No. 6-227866, Publication Date: Aug. 16, 1994. |
M. Isomura et al. "High-strength silicon nitride ceramics and their manufacture", Chemical Abstracts, vol. 118, No. 8, Abstract No. 65444, Feb. 22, 1993. |
Divisions (1)
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Number |
Date |
Country |
Parent |
912516 |
Aug 1997 |
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