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

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 x Ba(Sn 0.07 Ti 0.93 )O 3 -( 1 − x )Ba(Hf 0.1 Ti 0.9 )O 3 ferroelectric ceramics, where x = 0, 0.2, 0.4, 0.6, 0.8, and 1. Ba(Sn 0.07 Ti 0.93 )O 3 with an orthorhombic phase and Ba(Hf 0.1 Ti 0.9 )O 3 with a rhombohedral phase at room temperature were prepared beforehand as precursors, and phase-coexisted x BSnT-(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 Δ T = 2.16±0.08 K at 80 °C and 5 MV/m, and Δ T = 3.35±0.09 K at 80 °C and 7 MV/m.