Chemistry of Deoxidization Processes in Molten Ionic Halides

Physico-chemical peculiarities of interactions of oxide-containing admixtures in molten salts with different kinds of deoxidizing agents (halogen-containing gases, metal cations and getters) are analyzed in connection with the oxoacidic properties of the said melts. An approach giving possibility to extend the usability of existing experimental data to the case of melts possessing distinguished compositions is proposed. The juxtaposition of the obtained parameters of purification can be made using the primary medium effect of oxide ion (the oxobasicity index). Thermodynamic predictions and kinetic regularities of treatment of halide melts by action of gaseous hydrogen halides and halogen derivatives of hydrocarbons are discussed. The action of cations and getters on molten salts is considered on example of molten cesium iodide as initial material for the growth of optical single crystals. The efficiency of both deoxidizing agents increases with the rise of melting point of the formed metal oxide that makes this parameter to be the main criterion of choice of appropriate scavenger. The effect of cations and getters on the quality of the final optical crystals is shown.