Electrocaloric effect in BNT-based lead-free ceramics by local-structure and phase-boundary evolution

This work directly tests electrocaloric effect (ECE) of (0.94-x)Bi0.5Na0.5TiO3-0.06BaTiO(3)-xSrZrO(3) (BNBTSZx) with x = 0 (SZO), x = 0.01 (SZ0.01), x = 0.02 (SZ0.02) and x = 0.03 (SZ0.03) at different temperature points. The Sr-2(+) and Zr4+ are introduced into 0.94Bi(0.)(5)Na(0.5)TiO(3)-0.06BaTiO(3) to convert nonergodic relaxor phase into ergodic relaxor phase and form new morphotropic phase boundary (MPBII) at room temperature. A temperature change of 0.37 K and electrocaloric strength of 6.17 x 10(-3) K cm/kV are obtained at room temperature. According to the temperature dependence of Delta T and the electric-field dependence of electrocaloric strength, this work focus on the mechanism about higher electrocaloric effect at over-MPBII temperature point. Electrical performances, microstructure and piezoelectric properties are investigated in detail to analyze the local-area phase transformation causing the high electrocaloric effect. The electrocaloric strength of ergodic relaxor phase shows stronger dependence on the electric field than that of nonergodic relaxor phase. (C) 2019 Elsevier B.V. All rights reserved.