报告人：Prof. Andrew J Bell（University of Leeds, UK）
Inside Piezoelectricity: the structural origins of electromechanical coupling
In the quest for new piezoelectric materials, understanding how crystal chemistry impacts the intrinsic piezoelectric effect remains elusive. This study establishes a defining link between the piezoelectric coupling coefficient and differentials in observable structural variables, specifically strain and polarization, in both direct and converse effects. Notably, maximizing the piezoelectric coupling factor and charge coefficient requires significant displacements of cations, while, unexpectedly, minimal displacements of anions are optimal. Density Functional Theory (DFT) calculations on perovskites validate this, revealing enhanced charge and coupling coefficients when restricting oxygen ion displacements. The widely observed relationship between d33 and k33 in perovskite oxides is attributed to the invariant piezoelectric contribution of the oxygen sublattice. The study delves into anomalies in soft PZTs and relaxor-lead titanate single crystals, providing insights into their behaviors. These findings offer crucial crystal chemistry "design rules" for high-performance piezoelectric materials, particularly valuable in guiding the selection of functional groups for new organic piezoelectric materials with a larger design space than perovskite oxides.
Andrew Bell has been Professor of Electronic Materials at the University of Leeds, School of Chemical and Process Engineering since 2000. He was elected a Fellow of the Royal Academy of Engineering in 2016 and was elevated to Fellow of IEEE in 2019. He was awarded the Verulam Medal of the Institute of Materials in 2014. He has received the IEEE’s Ferroelectrics Recognition Award (2012) and Robert E Newnham Ferroelectrics Award (2022). His work on understanding the property enhancement mechanisms in Sm-doped piezoelectric ceramics won the American Ceramic Society’s Edward C Henry award for 2021. He is currently the 2023 IEEE-UFFC Distinguished Lecturer in Ferroelectrics. He has undertaken research on a wide range of topics in ferroelectric and dielectric materials, encompassing basic science, materials processing, structural & electrical characterization and device physics, including pyroelectric materials and devices, microwave dielectrics and piezoelectrics.