Dopant tuned multi-functionality in barium titanate based lead-free piezoceramics

With the increased concerns on the toxicity of lead, the barium titanate (BT) has developed a vital lead-free ferroelectric material to replace lead-based one due to the extraordinary multi-functionality. However, to date the deep understanding on evolution mechanisms of multiple electro-related performances in single BT based ceramics is still limited, and the simultaneous enhancement or balanced development of comprehensive performance in BT ceramics face challenges. Here, a new lead-free ceramic system of Ba _0.9+xSr _0.1-xTi _0.91Sn _0.09O ₃ (BSTS, 0 ≤ x ≤ 0.1) was successfully prepared by the conventional solid-state reaction method, and the dopant tuned multi-functionality and underlying physical mechanism of performance evolutions were revealed in detail. The BSTS ceramics present R-O-T-C multiphase coexistence at a wider temperature range near room temperature, along with the structural features with flattened thermodynamic energy landscape and flexible polarization rotation. Accordingly, the enhanced piezoelectric coefficient ( d ₃₃ = 600 pC/N), large electrostrictive coefficient ( Q ₃₃ = 0.0405 m ⁴/C ², E = 30 kV/cm), superior electrocaloric effect (Δ T = 0.77 K, E = 30 kV/cm) with a wider temperature span of 49 °C (Δ T > 0.5 K), and strong electrocaloric strength (Δ T/Δ E = 0.3857 K mm/kV, E = 5 kV/cm) are simultaneously attained under smaller electric field for BSTS ceramics. It exhibits a superior comprehensive performance than many reported BT based ceramics, which is suitable for more potential applications in the emerging fields of advanced functional devices, such as high precision displacement or strain actuators and zero-global-warming-potential refrigeration with larger capacity near room temperature. This work sheds insight into simultaneously optimizing different electro-related performances, and stimulates future studies on dopant tuned multi-functionality in BT based ceramics.