Using LiF and YF<sub>3</sub> as starting materials, we prepare feed material from fluorides according to the molar ratio of LiF:YF<sub>3</sub> = 51.5:48.5. The anhydrous LiYF<sub>4</sub> polycrystalline material is synthesized via the fluoridation process with a dried HF flow at elevated temperature. By charging the feed material and adding a small amount of active carbon powder in a sealed platinum crucible, the crystal can be grown via the vertical Bridgman method in a nonvacuum atmosphere. This is possible because the oxidization and volatilization of the melt is avoided. Using optimum conditions, that is, a growth rate of 0.5-0.6 mm/h and a temperature gradient of 25-30 ºC/cm across the solid-liquid interface under a furnace temperature of 920-930 ºC, the colorless crystal LiYF<sub>4</sub> with the size of φ25 x 50 (mm) is successfully grown. The optical transmittance of the crystal is as high as 85% above the absorption edge at 190 nm. The induced absorption bands are observed below 700 nm in the transmission spectrum after the crystal is subjected to a high dose of γ-ray irradiation.
© 2010 Chinese Optics Letters
Qishu Fang, Hongbing Chen, Fang Xu, Sujing Wang, Zhe Liang, and Chengyong Jiang, "Bridgman growth of LiYF4 single crystal in nonvacuum atmosphere," Chin. Opt. Lett. 8, 1071-1074 (2010)