Silicon nitride ceramic and a process for its preparation

Details Silicon nitride ceramic and a process for its preparation Silicon nitride ceramic and a process for its preparation

1991-10-07

1993-02-23

Bell, Mark L.

Plastic and nonmetallic article shaping or treating: processes

Including step of generating heat by friction

264 66, 501 98, 501 97, C04B32558, F04D 2926

Patent

active

051887819

ABSTRACT:
A process for the preparation of an Si.sub.3 N.sub.4 ceramic of high strength, wherein .alpha.-Si.sub.3 N.sub.4 powder is mixed with small amounts of at least one of the elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Y in form of an oxide or oxide precursor, the mixture is shaped to a shaped body and the shaped body is sintered under pressures of 1-100 bar in a nitrogen atmosphere at temperatures of 1,750.degree.-2,000.degree. C. is described.
The sintered body is heated at temperatures of 1200.degree.-1500.degree. C. in an inert gas atmosphere for at least 10 hours and then cooled. During this procedure, crystalline apatites of the formula A.sub.4+x (SiO.sub.4).sub.3 N.sub.x, A denoting the element added in the form of the oxide or oxide precursor and x denoting a number which is greater than zero and not more than 1.

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Eiji Tani et al., "Gas Pressure Sintering of Si.sub.3 N.sub.4 with an Oxide Addition", Yogyo-Kyokai-Shi, Journal of the Ceramic Society of Japan, vol. 94, No. 2, (1986) p. 303.
Chemical Abstract 87:10354d.

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