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 (Td) 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 Td of 175 °C can be simultaneously achieved by introducing Na0.5Bi4.5Ti4O15 into Na0.5Bi0.5TiO3 solid solution system. Structure resolution revealed that the diffusing of Na0.5Bi4.5Ti4O15 not only modifies the structures of TiO6 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 Td. Combined with enhanced room-temperature pyroelectric coefficient and high depolarization temperature, the Na0.5Bi0.5TiO3-xNa0.5Bi4.5Ti4O15 systems could be a promising lead-free pyroelectrics for uncool infrared detection.