Composition Dependence of the Transition Temperature for Non-Stochiometric Ferroelectric Lithium Niobate

Abstract

The transition temperature T _C (x) for non-stoichiometric lithium niobate, LiNbO ₃ , here denoted by (Li ₂ O) _x (Nb ₂ O ₅ ) _{1 − x} where 0.465 < x < 0.500, evolves from T _C (0.465) ≅ 1290 K to T _C (0.50) ≅ 1485 K. Using an effective field approach, as done in previous works for isomorphous ferroelectrics solid solutions, we investigate the composition dependence of the critical temperature in this narrow range for ferroelectric lithium niobate. Experimental data are fitted by the function T _C (x), deduced from the effective field theory when considering the short composition range of LiNbO ₃ as a mixed system with increasing stoichiometry.

Acknowledgments

The authors gratefully acknowledge to Dr. Angel Garcia Cabañes for helpful discussions and to Spanish MEC for financial support through the grant FIS 2004-00437.