Extend the scope of negative thermal expansion in PbTiO₃-based perovskites Available to Purchase

PbTiO₃ is a typical perovskite-type ferroelectric that shows unique negative thermal expansion (NTE) from room temperature to its Curie temperature (⁠ $α¯V$ = −1.99 × 10⁻⁵ K⁻¹, 300–763 K). It is widely accepted that enhanced NTE can be achieved in PbTiO₃-based ferroelectrics by improving the tetragonality of PbTiO₃ (c/a = 1.064) through chemical substitutions. Nevertheless, most substituted PbTiO₃-based ferroelectrics exhibit reduced tetragonality and weakened NTE, while enhanced NTE has only been achieved in those materials with enhanced tetragonality so far. Herein, we report on (1 − x)PbTiO₃-xBiAlO₃ solid solutions for which we observe reduced tetragonality accompanied by an unusual enhanced NTE (c/a = 1.057, $α¯V$ = −2.23 × 10⁻⁵ K⁻¹, 300–740 K), without much degradation of the NTE temperature range of pristine PbTiO₃ upon doping. The present study provides an example of unusual enhanced NTE accompanied by reduced tetragonality in PbTiO₃-based perovskites, which will extend the scope of NTE in PbTiO₃-based ferroelectrics and shed light on the understanding of enhanced NTE in PbTiO₃ family.