The impact of the simultaneous presence of Li and Nb(Ta) vacancies in the defect structure of pure LiBO3 (B=Nb, Ta) on the curie temperature

Abstract

The lithium niobate (LiNbO3, "LN") and lithium tantalate (LiTaO3, "LT") crystals are piezoelectric materials that exhibit intrinsic or extrinsic defect structures, which immediately impact their optical and electrical properties. In this study, we examine the influence of point defects on the Curie temperature (Tc) for different samples of pure LN and LT, using three vacancy models: the tantalum (niobium) vacancy model, the lithium vacancy model and the mixed lithium and tantalum (niobium) vacancy model. Based on the Safaryan approach, it was found that the calculated values for the tantalum (niobium) vacancy model did not agree with the experimental data. However, the lithium vacancy model and the mixed vacancy model showed good agreement between experimental and theoretical results. In conclusion, the proposed mixed vacancy model provides the best description of the defect structure in LN and LT materials, and the Tc, is influenced by the structural defects present in the LN and LT compounds.