Emergence of reentrant relaxor behavior with enhanced electromechanical and electrocaloric effect in Ba0.95Ca0.05Sn0.09Ti0.91O3 ceramic

Both A- and B-site-substituted BaTiO3 ceramics are promising alternative relaxor materials to replace lead zirconium titanate as an actuator. With a motivation to improve electromechanical properties, a lead-free Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramic close to the polymorphic phase boundary composition is synthesized by solid-state reaction. X-ray diffraction and Raman spectroscopy confirm the coexistence of orthorhombic (Amm2) and tetragonal (P4 mm) phases at room temperature. Our low-temperature dielectric study reveals the appearance of a reentrant relaxor state from the ferroelectric state near ∼150 K and is attributed to the coexistence of short and long ferroelectric ordered regions and slowing down of domain dynamics in the smaller regions, similar to the reentrant spin glass state observed in the system Fe-xAu. This feature is confirmed through glass model fitting parameters [ωo = 2.66(±0.28) × 108 Hz, Tg = 110(±1) K, zv = 4.5(±0.3)], and Mydosh parameter (“K” ∼ 0.05). The field-induced polarization (P–E) and strain (S–E) curves show well-defined slim ferroelectric and “butterfly-like” loops with a large value of maximum strain of ∼0.12%, an electromechanical coefficient of d*33 ∼ 1113 pm/V, and an electrostrictive coefficient of Q11 ∼ 0.048 m4/C2 at room temperature.