DEFECT-BASED DESCRIPTION OF LITHIUM DIFFUSION INTO LITHIUM-NIOBATE

A defect chemistry approach is used to analyze the observed concentration dependence of the lithium in-diffusion rate into lithium niobate. An ambipolar diffusion model is used where the lithium and niobium diffusion rates are coupled and therefore cause an internal electric field to develop during the diffusion process. Both lithium and niobium diffusion are found to proceed via simple vacancy mechanisms. The internal electric field forces the faster lithium diffusion to be reduced to a level consistent with the slower niobium diffusion process. This coupling gives a concentration dependence that matches the observed linear increase in interdiffusion rate as the total cation vacancy concentration decreases.