Thermodynamic Properties of the Melt of the NaI - CeI3 System

In the work presented here the determination of the chemical activities of the components NaI and CeI3 for the complete composition range of the NaI-CeI3 system is described as well as the partial pressures of the identified gaseous species. The obtaiened thermochemical data are important for fundamental research for the chemistry of molten salts and applied physical chemistry for the development of metal halide lamps. Metal halide lamps have achieved a widespread acceptance due to their high luminous efficiency and good colour quality. At the beginning of their developement these lamps were used for outdoor lighting e.g. the lighting of sportsfields. Since several years metal halide lamps are also used for indoor lighting and for the head lights of automobiles. The lamps contain a salt melt which in part vaporize under operating conditions. Important constituents of the melt are for example DyI3, CeI3, TmI3, and NaI.