The ever-growing demand for an alternative form of refrigeration led to a large research interest in the solid-state refrigeration technique based on the electrocaloric (EC) effect. However, a vivid depiction of the effect of defects (vacancies) on ECE in environmentally friendly EC materials in achieving large room temperature EC response ( T) over a wide temperature range is still an open challenge. In this regard, the heterovalent ion (La) doped BaTiO3 perovskites with vacancies to simultaneously tune the phase transition temperature (TC) and broaden the phase transition over a wide temperature range is systematically studied on Ba1-xLa2x/3TiO3 (x = 0.00, 0.01, 0.03, 0.05, 0.07, and 0.09) samples by the solid-state route. The X-ray diffraction analysis using Rietveld refinement reveals the co-existence of tetragonal and cubic symmetries with a reduction of tetragonal symmetry upon an increase in La doping. Raman spectroscopic studies confirm the existence of vacancy-induced modes upon La doping. The dielectric studies show a gradual decrease in TC and a transition from first-order to second-order with increased diffuseness () parameter. Room temperature P-E hysteresis loop measurements show a decreasing trend of Pr and EC with the increase in La content, indicating that the materials deviate from normal ferroelectric nature. The electron parametric resonance (EPR) measurements are performed to analyse the nature of induced defects. The temperature-dependent P-E hysteresis loop measurements show an imprint behaviour as a result of the introduction of defects. The fabricated samples are subjected to electrocaloric measurements. The ECE measurements show considerable value of adiabatic change in temperature (0.64 K at 40 kV/cm) close to room temperature. The obtained results will be used as a benchmark to further tune the system for better EC parameters.
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