Abstract: We studied the effect of non-stoichiometric ratio of Na⁺ and Bi³⁺ on the microstructure and electrical properties of Na_0.5+xBi_0.5-xTi_0.99Mg_0.01O_3-δ by adjusting the mole fractions of Na and Bi under the condition of maintaining constant total amount of A-site elements （x(Na)+x(Bi)=1） and  constant mole fraction of Mg doping. Samples of Na and Bi with different mole fractions were synthesized by using sodid-state method, and their structures and microstructures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties were evaluated by electrochemical testing. The results show that changing the mole fraction of Na and Bi can significatly affect the grain size and conductivity of the simple. The sample exhibits optimal grain and grain-boundary conductivity performance when x=0.02. Therefore, controlling the mole fraction of Na and Bi can effectively modulate the electrical performance of materials, providing experimental guidance for the development of high-performance oxygen ionic conductors.

Key words: non-stoichiometric ratio, oxygen ionic conductor, space charge potential, conductivity