Large electrocaloric efficiency over a broad temperature span in lead-free BaTiO3-based ceramics near room temperature

Abstract

We report a large electrocaloric efficiency of 0.029 K cm kV−1 at 303 K and in a wide operating temperature range of 293 K to 313 K in a lead-free Ba0.9Sr0.1(Ti0.9Zr0.1)0.95Sn0.05O3 ceramic by using direct electrocaloric effect (ECE) measurements. Sn4+ doping in Ba0.9Sr0.1Ti0.9Zr0.1O3 not only tunes the rhombohedral-to-paraelectric phase transition temperature to room temperature but also slightly widens the phase transition region, by slightly strengthening the diffuse character and maintaining its good ferroelectricity. Also, polar nanoregions embedded in the matrix facilitate polarization rotation because of a flat energy landscape associated with the relaxor-to-ferroelectric phase transition, inducing enhanced entropy changes and consequently excellent ECE performance.