Cation deficiency effect on negative thermal expansion of ferroelectric PbTiO3

Abstract

It is known that negative thermal expansion (NTE) in PbTiO₃ (PT) ferroelectrics can be controlled by chemical substitutions. In the present work, however, we report a method to change the NTE of PT by introducing cation deficiency at both the A (Pb²⁺) and B sites (Ti⁴⁺). We investigated the spontaneous polarization, tetragonality c/a, coefficient of thermal expansion, and Curie temperature T_C with 8% Pb²⁺ deficient PT (P₉₂T), 2% Ti⁴⁺ deficient PT (PT₉₈), and pure PT. We found that while Pb²⁺ deficiency distinctively weakens the NTE, the effect of B-site deficiency could be ignored. These phenomena are ascribed to the NTE mechanism of spontaneous volume ferroelectrostriction. The present study provides a possible way to control the NTE of PT-based materials.