Synergistic effects of Zn B-site substitution in lead-free Ba0.95Ca0.05Ti0.92Sn0.08O3 ferroelectric ceramics for enhancing piezoelectric properties in energy harvesting applications

Abstract

In this study, lead-free (Ba0.95Ca0.05)(Ti0.92Sn0.08)O3 (BCTS) and (Ba0.95Ca0.05)(Ti0.912Sn0.08Zn0.008)O3 (BCTS-Zn) ceramics with large piezoelectric properties were prepared via the conventional solid-state reaction. The effect of Zn B-site substitution on the structural, dielectric, ferroelectric, energy storage, electrocaloric and piezoelectric properties of BCTS ceramics were systematically investigated. X ray diffraction analysis and Raman spectroscopy of BCTS and BCTS-Zn ceramics confirm the formation of pure phase structure with the coexistence of orthorhombic, tetragonal and pseudo cubic phases at room temperature. The introduction of Zn into BCTS lattice resulted in a denser microstructure with larger average grain size which contributed in the enhancement of the dielectric constant maximum by ⁓35%. Furthermore, the substitution of Ti4+ with a small amount of Zn2+ (0.008) induced a shift in TR-O, TO-T and TT-C transitions towards higher temperatures in addition to an increase in the diffused phase transition character. Moreover, with Zn substitution, an amelioration in the maximum energy storage efficiency is observed from ⁓83% in BCTS ceramic to ⁓88% in BCTS-Zn ceramic. The electrocaloric properties were investigated using the direct and indirect methods. The highest value of the electrocaloric temperature change ΔT = 0.361 K at 319 K was calculated for BCTS ceramic using Maxwell approach with a relatively low electric field of 17.55 kV/cm. For BCTS-Zn ceramic, the enhancement of the piezoelectric properties (d33 = 420 pC/N, g33 = 23.02 mV/mN, FoM = 9.66 pm2/N) is attributed to the synergistic effect of the (O-PC-T) multiphase coexistence, large average grain size and high density of the ceramic. This study reveals that B site Zn substitution in BCTS lattice is an effective approach to improve the piezoelectric properties of the ceramic for energy harvesting applications.