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

Abstract

This work directly tests electrocaloric effect (ECE) of (0.94-x)Bi0.5Na0.5TiO3–0.06BaTiO3–xSrZrO3 (BNBTSZx) with x = 0 (SZ0), x = 0.01 (SZ0.01), x = 0.02 (SZ0.02) and x = 0.03 (SZ0.03) at different temperature points. The Sr2+ and Zr4+ are introduced into 0.94Bi0.5Na0.5TiO3–0.06BaTiO3 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 × 10−3 K cm/kV are obtained at room temperature. According to the temperature dependence of ΔT 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.