Thermal and electromechanical performance in BaSnO₃-modified potassium sodium niobate piezoceramics via two-step sintering

In view of industrial applications requiring high piezoelectric activity, KNN-based ceramics face two key constraints: insufficient density and temperature sensitivity. To address these challenges, this study first introduces BaSnO₃ and employs two-step sintering method (TSS) for fabrication, thereby synthesizing ternary 0.975K_0.5Na_0.5NbO₃-0.025Bi_0.5K_0.5TiO₃-xBaSnO₃ (KNN-1000xBaSn; x = 0, 0.3 %, 0.6 % and 0.9 %) with superior piezoelectricity (d₃₃ = 217–257 pC/N; d₃₃^* = 265–330 pm/V; S = 0.16–0.21 %), high Curie temperature (T_C = 325–349 °C) and densification (4.3–4.5 g/cm³; relatively density ∼96 %). In one respect, the TSS allows minimal volatilization of alkali metals while promoting grain homogenization. In another respect, the introduction of BaSnO₃ enhances the mobility of domain walls, meanwhile fosters diffuse phase transitions (DPT) and widens dielectric peaks without significantly impairing T_C. Moreover, the KNN–6BaSn obtain not only reinforced d₃₃ (256 pC/N) with high T_C (325 °C) and ε^′ (1016), but also fatigue resistance and extreme-temperature endurance with excellent d₃₃^* (445 pm/V at 90 °C; 300 pm/V at 180 °C). This work provides a resultful dual-strategy for the emergence of lead-free piezoelectric products.