LiGaTe2 (LGT) nonlinear crystal: Synthesis and crystal growth processes exploration

The LiGaTe₂ (LGT) single crystal up to 12 mm in size was grown in 3 stages: synthesis, homogenization and crystal growth. The initial charge with 6–10 at% excess of Li₂Te was produced by melting elementary Li, Ga and Te components. The homogenization step was carried out with the maximum value of melt overheating not exceeding 50 K. The Bridgman-Stockbarger technique was used to grow the LiGaTe₂ crystals. A furnace of special design, providing the enlargement of LGT linear size, was used. At each stage (synthesis, homogenization and crystal growth) the DTA analysis was carried out: during heating and cooling we recorded peaks corresponding to melting or crystallization of different components in the charge, such as Te⁰ (melting point 739 K) and LiGaTe₂ (melting point 945 K) and in the as-grown crystal. The XRD analysis was also carried out at each technological stage. The analysis showed that there are 2 side phases (Te⁰, Ga₂Te₃), and their phase contents decrease to 1.2 at%, while the LiGaTe₂ phase increases up to 93.5 at% during the homogenization process. The synthesized charge composition was analyzed by flame photometry (for Li) and atomic absorption (for Ga and Te). To provide a flat crystallization front and optimal conditions for crystal growth, spatial distribution of thermal field in the furnace was simulated. Transmission spectrum was recorded for the as-grown LGT crystal.