Enhanced room-temperature electrocaloric and pyroelectric responses around morphotropic phase boundary and energy storage performance of lead-free Ba0.85Ca0.15Hf0.10Ti0.90O3 ceramics sintered at various temperatures

Abstract

The electrocaloric (EC) cooling and energy storage capabilities of Pb-free ferroelectrics are thought to be a promising technology for developing environmentally friendly refrigeration and energy storage systems. The EC performance, energy storage and pyroelectric response of sol-gel derived Ba0.85Ca0.15Hf0.10Ti0.90O3 (BCHT) ferroelectrics sintered at various temperatures are investigated here. It is thoroughly explored how sintering temperature affects the structural and electrical characteristics of BCHT ceramics. According to structural analysis by X-ray diffraction, the morphotropic phase boundary (MPB) of tetragonal and orthorhombic phases is evolved in BCHT ceramics sintered at higher temperatures of 1250 and 1350 °C. The density, grain size, and dielectric constant of BCHT ceramics increase when the sintering temperature rises from 1150 to 1350 °C. The BCHT ceramic sintered at 1250 °C exhibits the highest room temperature pyroelectric coefficient p ∼ 15.21 10−4 C/m2K and the various pyroelectric figure of merits calculated are Fi = 7.46 10−10 m/V, Fv = 0.033 m2/C, FD = 31.82 10−6 Pa−1/2, Fe = 103.44 J/m3K2, and Fe* = 24.85 10−12 m3/J respectively. At the ambient temperature, BCHT ceramic sintered at 1250 °C with MPB displayed a high EC temperature change ΔT ∼ 0.56 K and EC efficiency ΔT/ΔE ∼ 0.28 Kmm/kV under relatively low field ΔE ∼ 20 kV/cm. The highest EC temperature change ΔT ∼ 1.01 K is also observed in BCHT ceramics sintered at 1250 °C with corresponding ΔT/ΔE ∼ 0.50 Kmm/kV at 87 °C. The observed values are higher than the value reported for other lead-free materials. The maximum recoverable energy density Jrec ∼ 116.18 10−3 J/cm3 and corresponding efficiency η ∼ 71.34 % has been observed in BCHT ceramics sintered at 1250 °C. These findings indicate that BCHT ceramics offer a promising way to develop high-performance pyroelectric sensors, electrocaloric refrigeration, and energy storage materials.