Enhancement of electrocaloric response and elevated energy-storage characteristics in lead-free BCTZ-ZN ceramics

Abstract

Recently, considerable focus has been on exploring the electrocaloric effect in environmentally friendly, lead-free ferroelectric materials. In this study, lead-free (Ba_0.95Ca_0.05)(Ti_0.95Zr_0.05)_1−x(Zn_1/3Nb_2/3)_xO₃ (BCTZ-xZN) ceramics were investigated. X-ray diffraction (XRD) analysis confirmed the formation of a pure perovskite structure with a structural phase transition depending on ZN substitution. Dielectric measurements revealed a diffuse phase transition and a shift in Curie temperature with increasing x. The electrical energy storage density (W_rec) was found to be 150 mJ cm⁻³ with an efficiency of η = 83% for BCTZ-2.5ZN. At an electric field strength of 25 kV cm⁻¹, a peak electrocaloric response of 0.68 K at 340 K was attained, with a corresponding electrocaloric responsivity of 0.27 K mm kV⁻¹ observed at 340 K for BCTZ-2.5ZN. The electrocaloric effect, combined with a calculated coefficient of performance (COP) of 2, demonstrates the material's potential for both cooling and energy storage. These findings underscore BCTZ-xZN as a promising material for applications in cooling systems and energy storage for electronic devices, offering versatile properties conducive to cooling operations via an external electric field across various operating temperatures.