Rare earth alkali metal bromides and chlorides

Phases in the alkali metal-rare earth metal-chloride, bromide and iodide systems... 

The change of halide ion results in weaker acidic properties for LnCl3 as compared with LnF3. This means that equilibrium (1.1.41) with the participation of alkali metal halide should be shifted to the left as compared with the fluoride complexes. That is, lithium chloride does not react with chlorides of the rare-earth elements with the formation of any compounds the binary phase diagrams are characterized by one simple eutectic. The same situation is observed for the binary diagrams for lithium- and rare-earth bromides. 

The mixed metal phases of the MX-RX3 (M = alkali metal, X-Cl, Br, I) systems are presented in table 32.10. Early work and new data for the chloride systems are described by Drobot et al. (1968). Additional results for the chlorides and data for the bromides and iodides are described by Kutscher and Schneider (1974). Investigations for all the rare earths are complete only for the NaCl and KCl systems. The absence of data for the lithium halide systems may indicate that intermediate phases are not formed data for the Rb systems are limited (Drobot,( l968). Comparison of the compositions in table 32.10 with those of the fluorides in table 32.9 show the formation of identical compositions except... 

Formation of such complex compoimds, but already with alkali-metal halides, has foimd application in the manufacture of modern metal halide lamps (Bom et al., 2004 Hilpert and Niemann, 1997), which have an emission spectmm close to that of the natural sunlight. Relevant iodides and bromides (particularly cerium and dysprosium bromides and iodides) were foimd to be the most suitable components of binary compoimds for the production of lamp vessels from silica glass (Markus et al., 2005). Further technological developments led to the replacement of vessel material by polycrystalline alumina and to the use of rare-earth chlorides for improving lamp characteristics (Rutkowska et al., 2004). 

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