High-entropy stabilized A-site cation occupancy in filled tungsten bronzes with great piezoelectric performance

The high-entropy design concept has been widely applied to perovskite ferroelectrics, leading to new compositions and promising functional properties. However, the structure–property relationships in filled tungsten bronze ferroelectrics designed via the high-entropy concept remain largely unexplored. In this work, a high-entropy tungsten bronze ceramic with nominal composition Ca 0.5 Sr 0.5 Ba 0.5 Pb 0.5 NaNb 5 O 15 (CSBPN) was synthesized by introducing Ca2 + and Pb2 + into the A-site of the structure. Structural analysis shows that CSBPN adopts an orthorhombic structure (space group Bbm2). This symmetry indicates the absence of non-180° domain walls, which is further supported by electron microscopy observations and electro-strain measurements. Dielectric measurements reveal a diffused phase transition associated with A-site compositional disorder, rather than relaxor characteristics. The XRD and dielectric results indicates structural stability under variations in temperature and applied electric field, which is attributed to the high-entropy effects of sluggish diffusion and severe lattice distortion. Hysteresis-free strain–electric field (S–E) loops were observed, suggesting that the field-induced strain is dominated by piezoelectric and electrostrictive contributions. The CSBPN ceramic exhibits d 33 = 72 pC/N, low Q m = 5, and strong anisotropy in electromechanical coupling ( k t = 0.46, k p = 0.15). These characteristics make CSBPN a promising candidate for piezoelectric ultrasonic detection.