Crystals of LiYF4 doped with Er, Er-Tm, and Er-Pr have been grown by the Top-Seeded Solution technique in an atmosphere of highly purified helium. Much of the technology developed for the fluoride crystal program supports the synthesis of highly purified low oxide content fluoride starting materials feed and provides the experimental basis for growth under conditions of very low recontamination of high-quality single crystals. The purification means are hydrofluorination at elevated temperatures of commercial rare-earth fluorides, zone-refining of either REF3 or LiREF4 compounds, and crystallization- purification by Czochralski growth. Crystal growth is carried out in pressure and vaccum-tight furnaces which, along with the charge, is outgassed to 0.000001 torr at elevated temperatures in preparation for a crystal growth run. The crystal growth is carried out in an atmosphere of He purified by passage through a quartz diffusion cell.
Semi-annual rept. no. 1, 5 Jun-5 Dec 1972
Prepared in cooperation with Massachusetts Inst. of Tech,. Cambridge. Dept. of Electrical Engineering.