Enhanced pyroelectric performance in Na0.5Bi0.5TiO3-xNa0.5Bi4.5Ti4O15 lead-free ferroelectric ceramics via composition and microstructure engineering

Lead-free pyroelectric materials with high room-temperature pyroelectric coefficient ( p) and depolarization temperature ( T _d) are in great demand for uncool infrared detectors. However, the state-of-the-art unleaded pyroelectric ceramics are confronted with challenge of increasing room-temperature pyroelectric coefficient at cost of declining depolarization temperature. Herein, we report that high room-temperature p of 5.28 × 10 ⁻⁴C m ^{− 2} K ⁻¹ with T _d of 175 °C can be simultaneously achieved by introducing Na _0.5Bi _4.5Ti ₄O ₁₅ into Na _0.5Bi _0.5TiO ₃ solid solution system. Structure resolution revealed that the diffusing of Na _0.5Bi _4.5Ti ₄O ₁₅ not only modifies the structures of TiO ₆ octahedra and wipes the P4bm nanodomains from the long-range ordered R3c phase, resulting in high remnant polarizations and enhanced room-temperature p , but also facilitates the electron transfer in the formation of Ti-O covalent bond and enhances the strength of Ti-O covalent bonds to improve the stability of crystal structure, leading to the enhancement of T _d. Combined with enhanced room-temperature pyroelectric coefficient and high depolarization temperature, the Na _0.5Bi _0.5TiO ₃- xNa _0.5Bi _4.5Ti ₄O ₁₅ systems could be a promising lead-free pyroelectrics for uncool infrared detection.