Influence of Vapor Transport Equilibration on Surface Composition of MgO:LiNbO3 Crystal

摘要

The surface composition of 5 mol% (in growth melt) MgO-doped z-cut LiNbO3 crystal was modified using Li-poor vapor transport equilibration (VTE) process. The VTE-induced surface Li2O-content reduction Delta C was evaluated from the measured birefringence, and the Delta C dependence on VTE temperature T and time t were studied. The results show that the effect of T on Delta C follows the Arrhenius law, with a surface Li2O-content reduction constant of (1.3 +/- 0.1) x 10(11) mol% and an activation energy of 3.0 +/- 0.1 eV, and the effect of t on Delta C is a square-root dependence, with Delta C = 0.17t(0.51). Thus, a generalized empirical expression can be obtained to show the dependence of Delta C on T and t. A comparative study on undoped pure LN shows that the MgO doping has slight effect on Delta C. Based on the obtained dependence of Delta C on t, the solution to the Li+ out-diffusion equation is shown and verified experimentally to be an integral of complimentary error function. The results indicate that Li-deficient MgO-doped LiNbO3 material with desired surface Li2O-content can be produced by controlling the VTE temperature and duration. (C) 2015 The Electrochemical Society. All rights reserved.