18O/16O isotope exchange in combination with SIMS depth-profiling was used to investigate oxygen transport in Li2O-deficient single crystalline LiNbO3 at 983 to 1188K under 200mbar of oxygen. Within the limits 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 temperature dependences for oxygen tracer diffusion were:

D (m2/s) = 6.4 x 10−3exp[−333(kJ/mol)/RT]

and, for oxygen surface exchange,

k (m/s) = 7.8 x 102exp[−288(kJ/mol)/RT]

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.

Oxygen-18 Surface Exchange and Diffusion in Li2O-Deficient Single Crystalline Lithium Niobate. P.Fielitz, G.Borchardt, R.A.De Souza, M.Martin, M.Masoud, P.Heitjans: Solid State Sciences, 2008, 10[6], 746-53