Enhanced temperature stability of flexoelectricity through high-entropy design

Abstract

Flexoelectricity is an electromechanical coupling phenomenon in which strain gradients induce electric polarization in solids, which have promising applications in flexible electronics, photovoltaic devices, and self-powered sensing systems. However, many flexoelectric materials suffer from poor thermal stability. High-entropy ceramics are materials characterized by multiple elements occupying lattice sites in near-equimolar ratios. The high configurational entropy is believed to stabilize phase structures and enhance the material's overall properties, especially temperature stability. This work employs the compositionally engineered high-entropy perovskite ceramics (Bi0.2X0.2Ba0.2Sr0.2Pb0.2) TiO3 (X = Li, Na, K) to elucidate the mechanisms governing the flexoelectric coefficients and their temperature stability via defect engineering and local strain modulation. Among these compositions, (Bi0.2Na0.2Ba0.2Sr0.2Pb0.2) TiO3 (HEC-Na) exhibits a well-defined perovskite structure and superior mechanical robustness, together with an optimized defect concentration and pinning landscape, as well as a reduced polarization barrier and weakened A–O bond strength. These synergistic factors collectively enhance flexoelectric performance and thermal stability in the HEC-Na system. This study provides a design strategy for next-generation high-sensitivity, thermally stable flexible mechatronic devices based on high-entropy perovskite ceramics.