Curie temperature of nonstoichiometric lithium tantalate and lithium niobate by a mixed vacancy model

Abstract

In this work, we present a new vacancy model which proves that both lithium and tantalate (niobium) vacancies can coexist in the lattice structure of lithium tantalate and lithium niobate. Using the theoretical approach to the defect structure analysis, which is developed by Safaryan, a comparison between three defect models (tantalate/niobium vacancies, lithium vacancies, and mixed vacancies) has been proposed. The calculated values of the Curie temperature for different compositions of nonstoichiometric lithium tantalate and lithium niobite show that the mixed vacancy model can effectively describe the defect structure in nonstoichiometric lithium tantalate and lithium niobate. Also, it can reveal good correspondence with experimental results.