Cation deficiency effect on negative thermal expansion of ferroelectric PbTiO3†
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 TC 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.