Li‐Rich/Li‐Poor Vapor Transport Equilibration Time Dependence of Surface Composition of Congruent LiNbO3 Crystal

Abstract

The influence of Li‐rich/Li‐poor vapor transport equilibration (VTE) at 1100°C on surface Li2O‐content of 1 mm thick, congruent X‐ and Z‐cut LiNbO3 crystal plates was studied against VTE duration. The VTE‐induced surface Li2O‐content alteration was determined from measured birefringence. The results show that the induced surface Li2O‐content alteration has a square root dependence on the VTE duration for both cases of Li‐rich and Li‐poor VTE. The dependence shows a slight effect of cut of plate and is stronger for the Z‐cut plate. The Li‐rich VTE duration required for surface composition reaching the stoichiometric boundary is similar to 20.0/15.6 h for the X‐/Z‐cut plate. In contrast, the Li‐poor VTE is a much slower process than the Li‐rich VTE. The Li‐poor duration required to reach the Li‐deficient boundary is 400/323 h for the X‐/Z‐cut plate. Based upon the known VTE duration dependence of surface Li2O‐content, a mathematical model is established and the solution to the diffusion equation, an integral of error function complement, is obtained and verified by previously reported experimental results on Li‐poor VTE.