Method for producing polycrystalline translucent alumina having

Details Method for producing polycrystalline translucent alumina having Method for producing polycrystalline translucent alumina having

1979-05-14

1980-09-16

Carter, Herbert T.

Plastic and nonmetallic article shaping or treating: processes

Including step of generating heat by friction

264 66, 264101, 220 21R, 106 734, 423625, C04B 3510

Patent

active

042229782

ABSTRACT:
Polycrystalline translucent alumina having an average grain size of alumina crystal grain being not smaller than 20.mu. and an average surface roughness of the fired body being not larger than 1/10 of the maximum grain size of alumina crystal grain and capable of being used for an envelope of a high pressure vapor discharge lamp, which is produced by shaping alumina composition powders consisting mainly of alumina into a given shape, primarily firing the shaped body under vacuum or in an atmosphere of hydrogen gas or dissociated ammonia gas at a temperature within 1,500.degree. C. and then secondarily firing the primarily fired body at a temperature of 1,650.degree.-1,900.degree. C., at least the temperature from 1,400.degree. C. to 1,700.degree. C. being raised at a rate of not lower than 200.degree. C./hr.

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patent: 4031177 (1977-06-01), Aurial et al.
patent: 4150317 (1979-04-01), Laska et al.
patent: 4169875 (1979-10-01), Laska et al.
Cahoon et al., "J. of the American Ceramic Soc.", vol. 39, 1956, pp. 337-344.

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