Field-driven merging of polarizations and enhanced electrocaloric effect in BaTiO3-based lead-free ceramics

Abstract

Abstract Solid-state cooling technology based on electrocaloric effect (ECE) has been advanced as an alternative to replace the vapour-compression approach to overcome the releasing of the global warming gases. However, the development in high ECE materials is still a challenge. In this work, polarization merging strategy was proposed to achieve a large ECE in xBa(Sn0.07Ti0.93)O3-(1−x)Ba(Hf0.1Ti0.9)O3 ferroelectric ceramics, where x = 0, 0.2, 0.4, 0.6, 0.8, and 1. Ba(Sn0.07Ti0.93)O3 with an orthorhombic phase and Ba(Hf0.1Ti0.9)O3 with a rhombohedral phase at room temperature were prepared beforehand as precursors, and phase-coexisted xBSnT-(1−x)BHfT ceramics were formed via a solid-state reaction approach. Phase coexisting structures were confirmed using the X-ray diffraction. The merged polarization was confirmed by the dielectric and ferroelectric properties. Optimal ECEs were obtained for 0.2BSnT-0.8BHfT ceramics, i.e., adiabatic temperature change ΔT = 2.16±0.08 K at 80 °C and 5 MV/m, and ΔT = 3.35±0.09 K at 80 °C and 7 MV/m.

Keywords

• lead-free ferroelectric
• microstructure
• permittivity
• polarization
• electrocaloric effect (ECE)