Lead-free Ba_(1-x)Sr_xTiO₃ ceramics for room-temperature pyroelectric energy conversion

Lead-free Ba_(1-x)Sr_xTiO₃ (BST) ceramics were fabricated to convert near-room-temperature waste heat to electric energy for creating self-powered and ‘battery-less’ systems. In comparison to thermoelectrics that are specifically used for harvesting heat with stable temperature span, pyroelectric converters based on Olsen cycle mechanism can harvest heat with temperature-vibration environment. Large energy conversion density (N_D) was obtained in BST ceramics within the narrower temperature gradient (< 60 °C). In terms of the diffused phase transition (DPT) in BST ceramics, the extra slim hysteresis loops processed relatively low coercive field (E_c) and hysteresis loss, which can effectively enhance the N_D owing to the wider electrical field interval. The effect of Curie temperature (T_c) tuned by the ratios of Ba/Sr on N_D and applicable range of temperature were also systematically examined. At the same electrical field difference (07 MV/m), the optimal energy conversion properties were gained around the T_c, e.g., 0.36 J/cm³ for BST66/³4 (T_c = 23 °C) within a temperature range between 25 °C and 65 °C, and 0.48 J/cm³ for BST72/28 (T_c = 43 °C) between 25 °C and 85 °C.