Phase Transitions and Nonlinear Optical Property Modifications in BaGaSe.

Phase transitions can change the crystal structure and modify the physical properties of crystals. In this work, we investigate the phase transition behavior in BaGaSe, an important middle infrared (mid-IR) nonlinear optical (NLO) crystal, in the temperature range from room temperature to 1173 K. Interestingly, the BaGaSe crystal undergoes a reversible ferroelastic phase transition at = 528 K, resulting in the presence of a newly discovered phase (γ-phase) at the higher temperature.