Large electrocaloric effect by disorder regulated structure in BaTiO3-based system

We report the effects of B-site cationic size disorder (σ2) and configurational entropy (CE) on the crystal structure and electrocaloric (EC) effect of BaTi1−x−ySnxZryO3 (BTSZ) (0.01 ≤ x ≤ 0.06) ceramics. The samples were designed to show decreased σ2 and increased CE but the same B-site cation average radius and tolerance factor with increasing x. The tetragonal lattice distortion c/a and piezoelectricity showed a minimum and maximum, respectively, near x = 0.04. The ferroelectric Curie temperature decreased overall from ∼358 to ∼332 K with x increasing from 0.01 to 0.06. The EC effects measured by the direct method showed a maximum with an adiabatic temperature change of ∼0.80 K at 60 kV/cm near x = 0.04. The large EC effect in x = 0.04 is attributed to the small tetragonal distortion and low energy barrier for E-induced phase transformation due to the combined disorder effects of cationic size and configuration. Our results suggest a close correlation between the lattice distortion and EC effects and an effective route to improve the EC effects.