Enhanced piezoelectricity and optical performance in Li⁺ ion modified BNT-based multifunctional ceramics

Transparent lead-free piezoelectric ceramics, crucial for multifunctional applications in cutting-edge industries, grapple with the dual challenge of achieving superior piezoelectricity and high transmittance, a delicate balance influenced by phase structure and grain size. In this work, we present a breakthrough in 0.9Bi_{0 · 5}Na_{0 · 5}TiO₃-0.1Bi_{0 · 5}Li_{0 · 5}TiO₃ (BNLT90) ceramic, outperforming other reported BNT-based transparent ceramics. BNLT90 showcases exceptional transmittance (T = 80.4% at 2000 nm) and robust piezoelectricity (d₃₃∼110 pC/N, k_p ∼ 20.6%). Li⁺ incorporation induces the coexistence of rhombohedral and pseudo-cubic phases, creating local lattice distortion and enhancing piezoelectric properties. Simultaneously, Bi_{0 · 5}Li_{0 · 5}TiO₃ (BLT) modification enhances relative density and reduces grain size, contributing to high transparency. Our results highlight A-site Li doping as a potent strategy for stabilizing the non-ergodic relaxor phase in BNT-based ceramics, offering insights for the precision development of piezoelectric transparent ceramics by regulating grain size and phase structure.