ISOTOPE EFFECT ON DISPLACIVE-TYPE FERROELECTRIC-PHASE-TRANSITION TEMPERATURES

The isotope effect on the ferroelectric transition temperature Tc is investigated within the polarizability model. The enhancement of any of the involved sublattice masses always yields an increase in Tc and its magnitude is a function of Tc. While the increase in the rigid-ion mass only induces a small enhancement of Tc, the replacement of the nonlinearly polarizable unit by its isotope shows large effects for small transition temperatures and is zero for high Tcs. © 1990 The American Physical Society.