Insight into the structure and functional application of Mg-doped Na 0.5 Bi 0.5 TiO 3 electrolyte for solid oxide fuel cells

Na0.5Bi0.5TiO3 (NBT) and its acceptor-doped perovskites, as lead-free piezoelectric materials before, have been found to be excellent oxygen-ion conductors with potential applications in intermediate temperature solid oxide fuel cells (SOFCs). Among them, the Bi deficient and B-site Mg doped sodium bismuth titanate (Na0.5Bi0.49Ti0.98Mg0.02O2.965, NBTM) exhibits a remarkable oxygen ionic conductivity. Here, we report a structural analysis on NBT and NBTM ceramics using high-temperature in situ neutron diffraction (NPD) to gain insight into the effects of Mg doping on ionic conductivity and structure. Both perovskite oxides exhibit two consecutive phase transformations from R3c to P4bm at ~400 C and from P4bm to Pm3m at ~600 C. The effects of Bi deficiency and Mg substitution on oxygen vacancy concentration and ion displacements are revealed. In addition, a NBTM supported single cell consisting of Ag- NBTM cathode and Ni-NBTM anode is fabricated to evaluate the possibility of its application in intermediate-temperature SOFCs. The structural stability of NBTM is still a major concern that hinders its utilization at high temperature and under reducing atmosphere.Fil: Lu, Yao. Chinese Academy of Sciences; República de ChinaFil: Lopez, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; Argentina. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Área Química General e Inorgánica; ArgentinaFil: Wang, Jie. Chinese Academy of Sciences; República de ChinaFil: Alonso, José Antonio. Consejo Superior de Investigaciones Científicas; España. Instituto de Ciencia de Materiales de Madrid; EspañaFil: Sun, Chunwen. Chinese Academy of Sciences; República de Chin