Polarization Rotation at Morphotropic Phase Boundary in New Lead-Free Na1/2Bi1/2V1–xTixO3 Piezoceramics

In this work, we show that polarization rotation enhances the piezoresponse in a high-performance lead-free piezoelectric material, Na1/2Bi1/2V1–xTixO3, a solid solution between tetragonal Na1/2Bi1/2VO3 and rhombohedral Na1/2Bi1/2TiO3, obtained by high-pressure synthesis. The system forms a pure perovskite structure with a favorable morphotropic phase boundary (MPB) located around x = 0.90, which separates the tetragonal and rhombohedral phases. In addition, a distinct monoclinic phase with polarization rotation as functions of composition and temperature is observed. XRD measurements revealed the moderately high Curie temperature of 523 K at x = 0.95 in the MPB. The piezoelectric coefficient d33 of the monoclinic x = 0.95 sample, 42 pC/N, is higher than those of the tetragonal and rhombohedral phases. Even though the present lead-free Na1/2Bi1/2V1–xTixO3 ceramics feature smaller d33 values compared to many currently available lead-free piezoelectric materials as a result of insufficient poling and low density, we expect our findings open up opportunities for exploring promising lead-free piezoelectric materials in Na1/2Bi1/2VO3-based perovskites.本研究表明，极化旋转可提升高性能无铅压电材料Na₁/₂Bi₁/₂V₁₋ₓTiₓO₃的压电响应。该材料为四方相Na₁/₂Bi₁/₂VO₃与菱方相Na₁/₂Bi₁/₂TiO₃形成的固溶体，通过高压合成法制备。该体系呈现纯钙钛矿结构，其准同型相界（morphotropic phase boundary, MPB）位于x=0.90附近，可区分四方相与菱方相。此外，研究观测到一种独特的单斜相，其极化旋转随组分与温度变化而改变。X射线衍射（XRD）测试显示，准同型相界组分x=0.95时，材料的居里温度可达523 K，处于中等偏高水平。单斜相x=0.95样品的压电系数d₃₃为42 pC/N，高于四方相与菱方相试样。尽管由于极化处理不充分与致密度较低，本研究制备的无铅Na₁/₂Bi₁/₂V₁₋ₓTiₓO₃陶瓷的压电系数低于当前多数商用无铅压电材料，但我们认为本研究结果可为基于Na₁/₂Bi₁/₂VO₃的钙钛矿体系中开发高性能无铅压电材料提供新的研究契机。