Silicon nitride base ceramic heater element and method of produc

Details Silicon nitride base ceramic heater element and method of produc Silicon nitride base ceramic heater element and method of produc

1989-05-30

1990-03-27

Reynolds, Bruce A.

Electric heating

Heating devices

With heating unit structure

219553, 219270, 501 97, 501 98, 123145A, H05B 312

Patent

active

049123050

ABSTRACT:
The invention relates to a ceramic heater element consisting of a sintered body of a silicon nitride base ceramic and a resistance heating wire such as a tungsten wire embedded in the ceramic body. The ceramic contains Al.sub.2 O.sub.3 and AlN besides Si.sub.3 N.sub.4 and is produced by using Y.sub.2 O.sub.3 as sintering aid. The ceramic body is improved in strength and also in stability of the ceramic structure at temperatures up to about 1300.degree. C. by rendering the grain boundary phase of the sintered ceramic a crystalline phase comprising either 2Y.sub.2 O.sub.3.Si.sub.2-x Al.sub.x N.sub.2-x O.sub.1-x (0.ltoreq.x<2) or 3Y.sub.2 O.sub.3.5Al.sub.2 O.sub.3. The heater element is produced by preparing a powder mixture in which (Si.sub.3 N.sub.4 +Al.sub.2 O.sub.3 +AlN) amounts to 90-98 wt %, the balance being the sintering aid, with proviso that (Al.sub.2 O.sub.3 +AlN)/Si.sub.3 N.sub.4 is from 0.02 to 0.08 by weight and that (Al.sub.2 O.sub.3 /AlN) is from 0.2 to 2.0 by weight, compacting the powder mixture into a desirably shaped body with insertion of the heating wire and sintering the shaped body preferably by a hot press sintering method. For example, the heater element is used in a glow plug for a diesel engine.

REFERENCES:
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patent: 4499192 (1985-02-01), Shimamori et al.
patent: 4556780 (1985-12-01), Atsumi et al.
patent: 4598676 (1986-07-01), Ito
patent: 4633064 (1986-12-01), Atsumi
patent: 4634837 (1987-01-01), Ito
patent: 4733056 (1988-03-01), Kojima

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