Synthesis and characterization of titanium doped sodium beta″-alumina

High dense Na–β″-Al2O3 electrolyte materials have been synthesized by solid state reaction with boehmite, magnesia, sodium carbonate and titania as the starting materials. The effects of TiO2 doping percentage on the properties and microstructures of the prepared samples were investigated by X-ray diffraction (XRD), scan electron microscope (SEM), three point bending and ionic conductivity tests. The results indicated that both the relative densities and the phase purities of the samples could effectively improved after doping with TiO2. The proper doping amount of TiO2 was to form the transient liquid phase during the sintering process, which would reduce the steric effect and accelerate the diffusivity. Moreover, the mechanical performance of the obtained sample increased to the value above 280 MPa as the doping amount of TiO2 was larger than 1 wt%. As to the electric properties, if the doping amount was less than 1 wt%, the grain boundary resistivity reduced as the density increased, so the ionic conductivity of the Na–β″-Al2O3 was enhanced obviously. However, when the doping amount was above 1 wt%, the ionic conductivity was deteriorated because of the increased resistivity caused by the broadening grain size.

► Since doping TiO2 can effectively increase the density of Na–β″-Al2O3 and thus improving its bending strength and ionic conductivity, a novel and simple method for synthesizing Na–β″-Al2O3 doping with TiO2 via solid state reaction is employed in this study. In this study, the effects of the amount of the dopant on contents of β″ phase, the grain size, the bending strength and the ionic conductivity of the synthetical Na–β″-Al2O3 are systematically investigated. For the first time, we systematically demonstrate the impact of the TiO2 content on the electrochemical performance of the solid electrolyte. The Na–β″-Al2O3 sample with 1 wt% TiO2 doping exhibits the best electrochemical performance.