Large electrocaloric responses in [Bi 1/2 (Na,K) 1/2 ]TiO ₃ ‐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 ]TiO 3 ‐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 Δ T =1.85 K and an electrocaloric responsivity of Δ T /Δ E =0.37 (10 −6 Km V −1 ) are found around room temperature (32°C). While in the Ta‐doped ceramic, BNKT‐1.5Ta, a wide operation temperature range ( T span ~55 K) 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.