Abstract
We report the effect of A-site disorder σ~2 on the structural, dielectric, ferroelectric (FE) and electrocaloric (EC) properties of lead-free Ba_(1-x-y)Sr_xCa_yTiO_3 (0.025 ≤ x ≤ 0.3, 0.275 ≤ y ≤ 0.113) perovskites. We have synthesized a series of samples with the same A-site cationic mean radius but different A-site ionic radii variance (i.e., A-site disorder) σ~2. The tetragonal distortion and FE Curie temperature TC are found to decrease with decreasing A-site disorder σ~2. The temperature of the maximum EC effect decreases from ~120-27 °C with decreasing disorder σ~2. The highest adiabatic temperature change ΔT obtained using both the direct and indirect methods reaches ~0.8 K for the sample with optimized A-site disorder σ~2. Our results suggest that, in addition to the lattice distortion, the lattice disorder might be a new and effective parameter for promoting the EC effect.
NSTL
Elsevier