Silicon nitride sintered bodies and a method for producing the s

Details Silicon nitride sintered bodies and a method for producing the s Silicon nitride sintered bodies and a method for producing the s

1983-06-08

1985-12-10

McCarthy, Helen M.

Compositions: ceramic

Ceramic compositions

Refractory

264 65, 501 98, C04B 3558

Patent

active

045580189

ABSTRACT:
Silicon nitride sintered bodies having particularly excellent strength and creep resistance at high temperatures, in which a total amount of MgO and Al.sub.2 O.sub.3 is more than 6% by weight and not more than 30% by weight and a weight ratio of MgO/Al.sub.2 O.sub.3 is 4-19, with the remainder being mainly Si.sub.3 N.sub.4. At least one of crystalline magnesium sialon represented by the general formula Mg.sub.x/2 Si.sub.6-y+x/2 Al.sub.y-x O.sub.y N.sub.8-y (O<x.ltoreq.y<8, preferably 0.9.ltoreq.x/y) and crystalline forsterite represented by the formula Mg.sub.2 SiO.sub.4 is contained as a second phase in addition to the main crystal of Si.sub.3 N.sub.4. The sintered bodies are produced by mixing a raw material powder of silicon nitride containing less than 2% by weight of oxygen with MgO and Al.sub.2 O.sub.3 so that a total amount of MgO and Al.sub.2 O.sub.3 is from 6% by weight to 30% by weight and a weight ratio of MgO/Al.sub.2 O.sub.3 is 4-19, and firing the resulting mixture at a temperature of 1,650.degree.-1,850.degree. C. in nitrogen or an inert gas atmosphere.

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Lange, F. F., "Silicon Nitride Polyphase Systems: Fabrication, Microstructure, and Properties"--International Metals Reviews, 1980, No. 1, pp. 1-20.

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