High‐Entropy High‐Temperature High‐Piezoelectricity Ceramics

Abstract High‐temperature piezoelectric materials are essential components of transducers and accelerometers applied in the fields of aircraft engines, automobiles, nuclear power units, etc., yet how to achieve large piezoelectricity accompanied by high Curie temperature and superior resistivity is still a big challenge. Here, the high‐entropy strategy is utilized to design bismuth‐layer high‐temperature piezoelectric ceramics, resulting in an excellent comprehensive piezoelectric performance with a record‐high figure of merit ( d 33 * T C ) and a high electrical DC resistivity of 1.0 × 10 6 Ω cm at 750 °C. High‐energy synchrotron X‐ray diffraction and transmission electron microscopy results suggest that there is no significant change in long‐range average orthorhombic structure through high‐entropy engineering, providing a structural basis for retaining a high T C . Encouragingly, highly dense bismuth‐layer vacancies occupied by alien atoms trigger extra unique out‐of‐plane polarization in perovskite layers around these 2D amorphous defects, as confirmed by quantitative analysis of local polarization configurations and density functional theory calculations. Together with the decreased polarization reversal energy barrier, the high entropy strategy benefits polarization flexibility under external stimulation and offers breakthroughs in electrical properties. This work provides new insight into the improvement of comprehensive functional properties through the cocktail effect and structure mechanism for designing novel high‐entropy materials.