Thermal stability and enhanced electrical properties of Er3+-modified Na0.5Bi4.5Ti4O15 lead-free piezoelectric ceramics

Abstract

Na_0.5Bi_4.5−xEr_xTi₄O₁₅ (NBET-x, x = 0, 0.006, 0.012, 0.018, 0.025) lead-free piezoelectric ceramics, with high electrical resistivity were prepared by a solid-state reaction route. X-ray diffraction analysis suggested that all compositions have a bismuth-layered perovskite structure and revealed a lattice distortion for the NBET-x ceramics. FE-SEM study confirmed that the plate-like morphologies for the grains were clearly observed for all the samples. The phase transition temperature shifted to higher temperatures with increasing Er³⁺ content. The activation energy value of the ionic conductivity suggested that defects were related to oxygen vacancies. The excellent electrical properties (e.g., d₃₃ ∼ 21 pC N⁻¹, 2P_r ∼ 17.2 μC cm⁻² and T_c ∼ 658 °C) are simultaneously obtained in the ceramics with x = 0.012. Additionally, the DC resistivity and thermal annealing behavior at elevated temperature indicated that the NBET-x ceramics exhibit good thermal stability, demonstrating that the NBET-x ceramics are promising candidates for high temperature piezoelectric applications.