Phase Transitions of Nonlinear Optical LiGaTe2 Crystals before and after Melting

5 years ago

Phase Transitions of Nonlinear Optical LiGaTe2 Crystals before and after Melting

Pavel G. Krinitsin, Ruslan E. Nikolaev, Inga G. Vasilyeva, Ludmila I. Isaenko

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 form the vapor pressure which increases with temperature due to the dissociation reactions in the melts. The most likely chemical forms of LiGaTe₂ and their structures are suggested on the basis of our own experimental measurements of the total pressure and composition of the vapor for LiGaTe₂ by adding the known 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 pressure of the melts. New thermochemical data obtained for LiGaTe₂ provide a significant contribution to the field of thermodynamic chemistry and are promising for understanding the precrystallization state of the melts which, in turn, can provide a guideline for optimizing the time–temperature regime of crystallization in order to improve chemical uniformity and optical quality of these crystals.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b04962

DOI: 10.1021/acs.jpcc.7b04962