Li-rich vapor transport equilibration temperature dependence of surface composition of initially congruent LiNbO ₃ Crystal

The influence of Li-rich vapor transport equilibration (VTE) on surface Li ₂O-content of 1-mm-thick, congruent X-, and Z-cut LiNbO ₃ crystal plates was studied against the VTE temperature. The VTE-induced surface Li ₂O-content increase was evaluated from measured birefringence. The results show that the increase follows the traditional Arrhenius law with a surface Li ₂O-content alteration constant (614 ± 136)/(91 ± 10) mol% and an activation energy (0.76 ± 0.05)/(0.53 ± 0.03) eV for the X/Z-cut plate. An empirical expression that correlates the VTE-induced surface Li ₂O-content alteration with both the VTE temperature and duration is presented. The expression is useful for producing a near-stoichiometric LiNbO ₃ plate with the desired surface Li ₂O-content via balancing the VTE temperature and duration.