Translucent ceramics as lamp envelopes

Abstract

The properties of oxide ceramics which may be sintered to translucency are discussed and it is shown that only alumina is at present suitable to prepare lamp arc tubes. A brief description of the preparation of alumina powder is given with particular emphasis on the properties of powders required for the manufacture of ware of optical quality. The processes involved in the manufacture of sintered translucent alumina are described, and it is pointed out that faults in sintered ware may be connected with problems in powder rheology. The theoretical limit to translucency in ceramics is examined, showing that purity and high sintered density of ware are essential. A method of producing hermetic seals in ceramic lamp arc tubes is also described.

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