Enhanced pyroelectric performance in potassium sodium niobate‐based ceramics via multisymmetries coexistence design

Achieving excellent pyroelectric performance remains a challenge for lead‐free piezoelectric ceramics. To meet the requirements of both an enhanced pyroelectric coefficient at room temperature and good thermal stability during the encapsulation of pyroelectric devices, (1–x)K0.48Na0.52NbO3–xBi0.5Ag0.5ZrO3–0.2%Fe2O3 (KNN–BAZ–Fe) lead‐free ferroelectric ceramics with high Curie temperatures were prepared to obtain improved pyroelectric performance via the coexistence of multiple symmetries. The variation of BAZ content led to the formation of rhombohedral–orthorhombic–tetragonal phase boundary and promoted grain growth, resulting in the best pyroelectric coefficient (p = 5.09 × 10−4 C m−2°C−1) and enhanced figures of merit (Fi = 0.2084 × 10−9 (m V−1), Fv = 0.0142 m2 C−1, Fd = 0.0947 × 10−4 Pa−1/2, and Fe = 17.66 J m−3 K−2) for infrared (IR) detection when x = 0.05. The room‐temperature pyroelectric coefficient obtained in this study is approximately four times that of the pure KNN ceramic and is the maximum value reported for niobate‐based piezoelectric ceramics. Moreover, compared with the poor thermal stability of barium titanate‐ and bismuth sodium titanate‐based ceramics because of their ultralow Curie temperature or thermal depolarization temperature, the ceramics investigated here exhibit much better thermal stability because of their high Curie temperature (TC > 300°C) and diffused phase‐transition behavior, making them more adaptable for practical applications. These results suggest that KNN–xBAZ–Fe ceramics are attractive candidates for applications in the field of IR sensors.