Oxygen-18 Surface Exchange and Diffusion in Li2O-deficient Single Crystalline Lithium Niobate

18O/16O isotope exchange in combination with SIMS depth profiling was used to investigate oxygen transport in Li2O-deficient single crystalline LiNbO3 in the temperature range 983 ≤ T/K ≤ 1188 at 200 mbar oxygen. Within the limit of experimental error and for the investigated range of temperatures no significant differences between transport parallel and transport perpendicular to the c-axis were found. The following temperature dependencies were determined: for oxygen tracer diffusion D = 6.4 × 10−3exp[−333 kJ/mol/(RT)] m2/s; and for oxygen surface exchange k = 7.8 × 102exp[−288 kJ mol−1/(RT)] m/s. The activation enthalpy obtained for tracer diffusion can be interpreted as the enthalpy of migration of extrinsic oxygen vacancies induced by impurities with lower valency on niobium sites.