Comments on the defect chemistry of magnesium-doped lithium niobate (LiNbO3)

Abstract

Congruently grown LiNbO3 is known to be highly defective due to its significant Li2O deficiency. At present two stoichiometry-related defect-chemical models are discussed which can be distinguished with respect to the occurrence of Li or Nb vacancies, The Nb-vacancy model takes advantage of ilmenite-structured LiNbO3 and predicts a niobium antisite concentration being at least five times as large as in the Li-vacancy model, In the present contribution it is argued that the magnesium-doping mechanisms are essentially independent of these particular differences. It is argued that extended stoichiometry-related defect clusters represent a key for a proper understanding of the defect chemistry of impurity cations, The discussion is mainly based on our recent shell-model simulations of perfect and defective LiNbO3. (C) 1996 Academic Press, Inc.