Enhanced energy-storage performance and electric-field-induced strain in Ta-doped (Bi0.465Na0.465Ba0.07)TiO3 lead-free ceramics

Abstract

The influence of Ta5+ substitution on lead-free (Bi0.465Na0.465Ba0.07)TaxTi(1–x)O3 (BNBT–xTa, x = 0.0 to 0.03) ceramics was investigated. The samples were prepared using a conventional solid-state route, resulting in a phase-pure perovskite structure with pseudocubic characteristics for all compositions. With increasing Ta content, the electrical response gradually shifted toward relaxor behavior, as indicated by slimmer P–E loops, reduced remanent polarization, and a shift of Ts toward lower temperatures. This transition was also reflected in the strain characteristics, where S–E loops evolved from typical butterfly shapes to sprout-like profiles. The sample with x = 0.01 showed the best strain performance, reaching ~0.23% strain along with a normalized coefficient of ~383 pm·V‒1. Energy-storage performance was significantly improved, with a maximum Wrec of ~0.90 J·cm‒3 for x = 0.02, while efficiency further increased to 68% for x = 0.03. In parallel, electrical resistivity increased by nearly an order of magnitude, accompanied by a rise in activation energy from 1.53 eV to 1.71 eV, suggesting suppressed charge transport due to enhanced energy barriers. Overall, Ta5+ substitution effectively tailors both electrical and electromechanical properties, making BNBT-based ceramics promising candidates for advanced lead-free capacitor applications and actuators.