Improved electrical and bioactivities of lead-free BNT–SBT ceramics by STZ additive and post-sintering processes

Abstract

This study examined the effects of Sr(Ti_0.85Zr_0.15)O₃ (STZ) additive and post-sintering treatments on the electrical and biological properties of lead-free (1 − x)[0.7(Bi_0.5Na_0.5)TiO₃–0.3(Sr_0.7Bi_0.2)TiO₃]–xSr(Ti_0.85Zr_0.15)O₃ or ((1 − x)(BNT–SBT)–xSTZ) ceramics synthesized by solid-state reaction. All compositions showed coexistence of rhombohedral and tetragonal phases, with increased STZ promoting the rhombohedral phase. The x = 0.15 composition exhibited favorable results, featuring a broad temperature coefficient of capacitance (TCC) stability range (±15% from 38–310 °C), a 43% increase in energy storage density, 92.90% energy efficiency, strong breakdown strength (95 kV cm⁻¹), and excellent thermal stability, with only 1.48% energy density variation between 25 and 125 °C. Its initial electrostrain of 0.06% was notably low. Post-sintering aging enhanced electrostrain to 0.33% representing a 450% increase and significantly improving electromechanical response. Cytotoxicity testing confirmed excellent cell viability, and bioactivity in simulated body fluid, initially moderate, was notably enhanced by β-tricalcium phosphate surface coating. These results highlight the biomedical potential of the optimized x = 0.15 ceramic composition.