Phase Transitions of Nonlinear Optical LiGaTe2 Crystals before and after Melting

Abstract

Phase transitions of ternary LiGaTe2 crystals with the chalcopyrite structure were investigated between temperatures 920 and 1300 K using traditional and high-speed thermal analyses together with static tensimetric methods. It was found that solid LiGaTe2 melts congruently at 940 K without any sublimation. The vapor involving Ga and Te species occurs at 953 K whereas the Li species are detected only above 1000 K. The lattice stability of solid LiGaTe2 holds up to the melting point, but the liquid phase begins to produce the vapor pressure increasing with temperature due to dissociation reactions in the melts. The most likely chemical forms of LiGaTe2 and their structures are suggested based on own experimental measurements of the total pressure and composition of the vapor for LiGaTe2 adding the know information on the chemical bonds and structures of the liquid individual binary Li2Te and Ga2Te3 as constituents of the ternary LiGaTe2. The changes are presented in the scale of temperature and the vapor pr...