Stacking-Fault Model for Stoichiometry Deviations in LiNbO3 and LiTaO3 and the Effect on the Curie Temperature

Abstract

Several arrangements are suggested to explain deviations from stoichiometry in LiNbO3 in a recent report by Lerner, Legras, and Dumas. These arrangements are considered to be unlikely, and an alternative mechanism in terms of partial stacking faults is proposed for LiNbO3 and LiTaO3. A microscopic statistical theory of ferroelectricity, which is outlined, can predict the variation of the Curie temperature with changes in the bonding forces and atomic masses. Using this approach, the stacking-fault model is consistent with the observed variation of Curie temperature with composition.