Patent ID: 6860942

Claim:
A process for preparing a fluoride optical crystal pre-melt material suitable to manufacturing fluoride optical crystals, said process comprising: (a) loading a permeable graphite crucible with a metal fluoride compound or a mixture of metal fluoride compounds and a metal fluorinating agent; (b) placing the loaded crucible of step (a) into a furnace capable reaching a temperature of at least 1600° C.; (c) heating the mixture to a selected temperature above the melting point of the metal fluoride compound over a first selected time period; (d) holding the mixture of step (b) at the selected temperature for a second selected time period; and (e) cooling the material of step (d) to room temperature over a third selected time period; wherein the metal of the metal fluoride compound or mixture of metal fluoride compounds is different from the metal of the metal fluorinating agent.