Chemistry of metal halide lamps: a review

Abstract

Metal halide lamps are complex high temperature chemical systems which are neither closed (with respect to material flow) nor well defined thermochemically. This complexity, coupled with the commercial importance of this lamp type, has spurred the development of several models which attempt to describe the chemical (and physical) phenomena which occur. This paper reviews the published literature over the past decade which treats the chemical phenomena and the modelling of these processes. The emphases in the paper are three: (1) the availability of pertinent thermochemical data and the bases for these data; (2) material requirements and limitations; and (3) observed chemical interactions among the chemical additives, the envelope, electrode materials, and impurities. A brief discussion of transport processes (chemical, convective, diffusive) is included.