Large electrocaloric responses in [Bi1/2(Na,K)1/2]TiO3-based ceramics with giant electro-strains

The electrocaloric effect (ECE) is investigated through indirect measurement in two lead-free [Bi-1/2(Na,K)(1/2)]TiO3-based ceramics that were previously reported to display giant electro-strains. In the Nb-doped ceramic, denoted as BNKT-2.5Nb, a decent temperature change of T=1.85K and an electrocaloric responsivity of T/E=0.37 (10(-6)KmV(-1)) are found around room temperature (32 degrees C). While in the Ta-doped ceramic, BNKT-1.5Ta, a wide operation temperature range (T-span similar to 55K) is observed near room temperature. Additional electrical measurements, as well as transmission electron microscopy experiments, are performed to identify the mechanisms of the ECE in both ceramics.