Enhancement of High-Temperature Piezoelectric Properties in V/Mn Co-Doped Sr2Nb2O7 Ceramics

Abstract

Enhancing the piezoelectric response of the perovskite-layered structure (PLS) ceramic Sr₂Nb₂O₇ is essential for high-temperature piezoelectric sensing. Here, V/Mn co-doping was employed to improve the performance of Sr₂Nb₂O₇ (SNVMx) ceramics. Structural refinement combined with Shimakawa-model calculations indicates an increased spontaneous polarization upon V/Mn incorporation, associated with an enlarged separation between the centers of positive and negative charges. High-resolution TEM and SAED reveal the features of both superlattice and local defect-related microstructural heterogeneity, suggesting dopant-induced structural modulation and local strain fields that may contribute to an enhanced intrinsic electromechanical response. Piezoresponse force microscopy further shows enlarged domain features, increased piezoresponse amplitude, and reduced local coercive voltage (V_C) in the doped ceramics, implying facilitated switching and improved domain-wall mobility, i.e., a strengthened extrinsic contribution. Consequently, the piezoelectric coefficient reaches d₃₃ ≈ 3.5 pC/N while maintaining a T_C above 1200 °C. Moreover, depolarization tests confirm stable piezoelectric performance after annealing up to 800 °C, supporting the potential of V/Mn co-doped Sr₂Nb₂O₇ for high-temperature applications.