Impact of Ca2+ and Zr4+ substitution on mechanical energy harvesting response of lead-free BaTiO3 piezoceramics with thermally stable storage density and efficiency

Abstract

The Ba1-xCaxZryTi1-yO3 (BCZT; x = 0.18, y = 0.08; x = 0.15, y = 0.10; x = 0.12, y = 0.12; x = 0.09, y = 0.14; both x and y are in mol. %) piezoceramics were prepared by solid-state reaction method and investigated their energy storage and harvesting responses. The composition x = 0.15, y = 0.10 ( i.e. BCZT-2) reveals the morphotropic phase boundary (MPB) near room temperature with enhanced piezoelectric properties such as piezoelectric charge coefficient (d33) ~ 380 pC/N, piezoelectric strain coefficient (d33*) ~ 583.71pm/V, piezoelectric voltage coefficient (g33) ~ 14.09 ×10-3Vm/N, figure of merits (d33×g33) ~ 5.35 ×10-12m2/N and the electromechanical coupling coefficient (kp) ~ 0.291. The harvested peak-to-peak open circuit AC voltage is 30V and the calculated current is in the range of 0.02 to 0.14mA with varied load resistance and the maximum obtained power density is 13.38 μW/mm3 for BCZT-2 ceramics. The DC output signal of BCZT-2 ceramics successfully lit up the 'FCLNT' panel consisting of 53 red LEDs. At room temperature, BCZT ceramics have a recoverable energy storage density (Wrec) and storage efficiency (η) in the range between 506.46 - 257.49 mJ/cm3 and 50.53 – 64.93% respectively. The composition x = 0.12, y = 0.12 (i.e. BCZT-3) revealed the highest energy storage efficiency (η) ~ 64.93% at room temperature. Nonetheless, the temperature-dependent (till its Curie temperature) maximum obtained Wrec of all BCZT ceramics is found in the range between 238.41 to 446.49 mJ/cm3 with an η of 66.98% to 79.67%. Thus, compositionally tuned BCZT ceramics exhibit considerable piezoelectric properties, including energy storage and harvesting capabilities.