Influence of Parameters in Vapor Transport Equilibration Treatment on Composition and Homogeneity of LiTaO₃ Single Crystals

The effect of key parameters such as time, temperature, and equilibration powder concentration in vapor transport equilibration (VTE) treatment on the Li 2 O content of initially congruent X‐, Y‐, and Z‐cut LiTaO 3 crystals is experimentally investigated. The Li 2 O content across the thickness of the crystal is estimated by Raman spectroscopy with accuracy of 0.05–0.15 mol%. The Li 2 O loss from equilibration powders has been monitored as a function of treatment temperature and duration. The results show that the Li 2 O content in the crystal nonlinearly depends on the equilibration powder composition and that homogeneous stoichiometric LiTaO 3 crystals can be obtained by treatment for at least 36h at 1250°C in Li 2 O‐rich atmosphere, created by powders containing >54 mol% of Li 2 O. The anisotropic Li + diffusion coefficients and its activation energy are also experimentally estimated. Finally, the VTE conditions are defined for the production of different cuts of LiTaO 3 crystals with controlled homogeneous Li 2 O nonstoichiometry in the range from subcongruent to stoichiometric compositions.