Silicon nitride sintered bodies and process for manufacturing th

Details Silicon nitride sintered bodies and process for manufacturing th Silicon nitride sintered bodies and process for manufacturing th

1987-06-04

1989-01-03

Lander, Ferris H.

Compositions: ceramic

Ceramic compositions

Refractory

501 96, 501 97, 264 65, C04B 3558

Patent

active

047957247

ABSTRACT:
Silicon nitride sintered bodies are disclosed, which each consist essentially of Si, O, N, and at least two kinds of rare earth elements selected from Y, Er, Tm, Yb, and Lu the bodies comprising not less than 70% by weight of Si.sub.3 N.sub.4. The ratio of the molar amount of all the rare earth elements contained in the sintered body calculated as moles of Ln.sub.2 O.sub.3, Ln being a rare earth element selected from Y, Er. Tm, Yb and Lu divided by the molar amount of oxygen calculated as moles of SiO.sub.2 is within the range of from 0.4 to 1.3. The amount of oxygen calculated as moles of SiO.sub.2 is obtained by subtracting the amount of oxygen contained in all the Ln.sub.2 O.sub.3, all the rare earth elements contained in said sintered body being considered as molecules of Ln.sub.2 O.sub.3 from the amount of oxygen contained in the sintered body and converting the remaining amount of oxygen into moles of SiO.sub.2. Any one of the rare earth elements contained in the sintered body accounts for not more than 95 mol % of all the rare earth elements contained in the sintered body. An intergranular phase of Si.sub.3 N.sub.4 grains contained in the sintered body is substantially of a crystalline phase and not less than 50% of the crystalline phase of the intergranular phase is a crystalline phases of an apatite structure. A process for manufacturing such silicon nitride sintered bodies is also disclosed.

REFERENCES:
patent: 4234343 (1980-11-01), Andersson
patent: 4511525 (1985-04-01), Tsuge et al.
patent: 4535063 (1985-08-01), Matsuhiro et al.
Effect of Crystallizing the Grain-Boundary Glass Phase on the High-Temperature Strength of Hot-Pressed Si.sub.3 N.sub.4 Containing Y.sub.2 O.sub.3, Tsuge et al., J. Amer. Ceram. Soc. 58, 323-326 (1975).
Japanese Industrial Standard, "Testing Method for Flexural Strength (Modulus of Rupture) of High Performance Ceramics", JIS R 1601-1981 JCPDS Card 30-1462.
In Re Durden 226, USPQ 359.

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