A formula for the soft-mode frequency and Curie temperature (based upon the ion-mass, charge, and distances between them) was applied to an analysis of the defect structure of non-stoichiometric samples. Four compositions were studied, ranging from near-stoichiometric to very Li2O-deficient; including congruent. The Curie temperatures were calculated for various types of defect: O vacancies, Nb vacancies and Li vacancies. A comparison of calculated and experimental values showed that the O and Nb vacancy models did not agree with experimental data. A good quantitative agreement between the calculated and experimental data, for the Li vacancy model, permitted the conclusion to be drawn that this model best described the defect structure of non-stoichiometric material.

An Approach to the Defect Structure Analysis of Lithium Niobate Single Crystals. F.P.Safaryan, R.S.Feigelson, A.M.Petrosyan: Journal of Applied Physics, 1999, 85[12], 8079-82