Reactive atmosphere crystal growth method

Claim 1

A processing method for growing ultra pure laser quality single crystals from alkali metal halide powders selected from the group consisting of alkali metal chlorides, alkali metal bromides, and alkali metal iodides whereby material purification and crystal growth occurs in a continuous uninterrupted sequence, comprising: charging a crucible with said powders and mounting said crucible in a furnace, increasing the temperature of said furnace to a level sufficient to cause said powders to melt and remain molten thereby creating an environment which will ensure the dissociation of selected halogen source gasses which are subsequently introduced into said furnace, purging contaminants from the interior surface of said crucible, which simultaneously scrubbing said molten charge to remove cation and anion impurities, by flowing a nascent halogen source gas, selected from the group whose formula is RY n X 4-n where R is carbon, Y is a strongly covalently bonded atomic substituent, X is a halogen and n ranges from 1 to 3, having a dissociatable halogen which corresponds to the halide of the alkali halide being grown, in a carrier gas selected from the group consisting of He, CO 2 and mixtures of He and CO 2 , through said furnace at a preselected carrier gas - halogen source material ratio and a gaseous flow rate based on the preselected halogen source material decay constant whereby the formation of nascent halogens is favored for an extended time interval ranging from 50 to 70 hours, and causing a single crystal to be formed from said melt in the presence of said flowing halogen gas by slowly removing said crucible from said furnace and allowing said crystal to slowly cool to ambient temperature while maintaining a constant purge of said halogen gas.