Wu J.; Zhang H.; Huang C.-H.; Tseng C.-W.; Meng N.; Koval V.; Chou Y.-C.; Zhang Z.; Yan H.YI-CHIA CHOU2022-06-302022-06-30202022112855https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086828075&doi=10.1016%2fj.nanoen.2020.105037&partnerID=40&md5=07081f5af9b5bea7761225c4d287ecf7https://scholars.lib.ntu.edu.tw/handle/123456789/614656Due to the worldwide concerns of environmental protection and sustainable development, lead-free piezoelectric materials are greatly desired for bridging the electrical energy to the mechanical energy. However, their lower energy conversion coefficient compared to the conventional lead-containing piezoelectric materials significantly limits their device applications. Herein, we introduce a novel strategy to increase the strain of lead-free ferroelectric system via material structure design to create polar nano regions (PNRs) and point defects in the material while retaining the global ferroelectric phase. This added short-range structural heterogeneity in the material will facilitate the field-induced phase transition and reversible domain wall switching to enhance the strain. Following this strategy, we demonstrate an ultrahigh strain induced by an electric field in non-textured lead-free Bi0.5Na0.5TiO3 (BNT)-based ceramics. The strain in unipolar mode (Suni) can reach up to 0.74% at 70 kV/cm, making it the highest value in reported lead-free ceramics so far. This puts forward a good route to design high-performance piezoelectric materials by material structure engineering. It also reveals the promising potential of lead-free piezoelectric materials in practical electromechanical device applications. © 2020 The AuthorsBismuth compounds; Domain walls; Energy conversion; Environmental protection; Ferroelectricity; Piezoelectric materials; Piezoelectricity; Point defects; Sodium compounds; Sustainable development; Textures; Titanium compounds; Conversion coefficients; Device application; Ferroelectric phase; Field-induced phase transition; Lead-free ferroelectrics; Lead-free piezoelectric materials; Mechanical energies; Structural heterogeneity; Electromechanical devicesjournal article10.1016/j.nanoen.2020.1050372-s2.0-85086828075