The effect of doping on oxygen conductivity performance of Na_0.5Bi_0.5TiO₃ compounds

The three different doped (Na, K and Mg) Na_0.5Bi_0.5TiO₃ compounds were prepared. The grain conductivity of the doped Na_0.5Bi_0.5TiO₃ compounds shows: Na-doping > K-doping > Mg-doping. Using the dielectric relaxation spectroscopy, the relaxation parameters can be obtained: E_Na = 0.61 eV, E_K = 0.64 eV and E_Mg = 0.68 eV. In the Na-doped Na_0.5Bi_0.5TiO₃ compound, there exists the lowest activation energy, best oxygen vacancy mobility and the disorder decrease of A-site sub-lattice in the Na_0.5Bi_0.5TiO₃ compound from the Na-doping on the A (Bi³⁺)-site, which are the possible reasons for the higher grain conductivity in the Na-doped Na_0.5Bi_0.5TiO₃ compound. In the Mg-doped Na_0.5Bi_0.5TiO₃ compound, despite the worst oxygen vacancy mobility, the concentration of mobilizable oxygen vacancies is almost highest, which can be adopted to increase the mobilizable oxygen vacancy concentration of the Na-doped Na_0.5Bi_0.5TiO₃ compound. For the Na_0.5Bi_0.5TiO₃ compound, the further improvement of the electrical performance can be expected for the slight amount Mg-doping on the Ti⁴⁺-sites in the Na-doped Na_0.5Bi_0.5TiO₃ compound, which is meaningful to obtain the higher oxide ionic conductivity in the Na_0.5Bi_0.5TiO₃ compounds.