Influence of La₂O₃ addition on the electrical properties of Na–β(β″)-Al₂O₃ solid electrolyte

Na–β(β″)-Al₂O₃ solid electrolyte materials were synthesized using the traditional solid-state reaction technique and modified by La2O3 doping in this paper. A systematic investigation into the effects of La₂O₃ doping on the microstructure and electrical properties of Na–β(β″)-Al₂O₃ was conducted using XRD, SEM, and an electrochemical workstation. The results showed that the Na–β(β″)-Al₂O₃ solid electrolyte, when doped with an appropriate amount of La₂O₃, exhibited an increased β″-Al₂O₃ phase content and a uniform microstructure characterized by dense and well-formed grains. However, excessive doping of La₂O₃ led to the formation of LaAlO₃ impurities and a reduction in density, which consequently resulted in a decline in ion conductivity. The optimized sample, doped with 0.50 wt% La₂O₃ and a sintered at 1620 °C, exhibited a composition comprising 83.45% of the β″-Al₂O₃ phase. It exhibited a uniform and compact microstructure, achieving a relative density of 96.02% (3.1298 g cm⁻³) compared to the theoretical density, along with a minimum AC impedance value of 4.37 Ω. Compared to the non-doped sample, which exhibited an ionic conductivity of 0.0156 S cm⁻¹ at 300 °C and a conductance activation energy of 0.1453 eV, the optimized sample demonstrated significantly enhanced ionic conductivity (0.027 S cm^⁻1 at 300 °C) and a reduced conductance activation energy of 0.1055 eV. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature, 2025.