Study to Determine the Feasibility of Utilizing Skull-Melting Techniques for the Growth of Single Crystals of Yttrium Vanadate

摘要

The goal of this program is to explore the feasibility of utilizing RF induction heated skull-melting techniques for the growth of optical quality crystals of yttrium vanadate (YVO4). In a parallel effort, experiments were also carried out to explore the fusion and recrystallization of yttrium aluminum garnet (YAG) in a cold crucible. Yttrium vanadate melts were achieved in cold crucibles up to 157 mm in diameter operating at an RF frequency of 3 MHz. However, attempts to Czochralski crystal growth were not successful due to poor thermal geometry and dissociation of the skull-contained melt. Experiments suggest that oxygen overpressures in excess of 2 atmos. may be useful in suppressing the dissociation rate of YVO4 melts. Skull-melting of YAG was achieved using an RF frequency of 3 MHz (no melting was observed at lower frequencies). However, the melts tended to slowly de-couple and freeze spontaneously; stable melts could not be maintained for periods beyond 2-3 hours.