Na_0.5Bi_0.5TiO₃ (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 (Na_0.5Bi_0.49Ti_0.98Mg_0.02O_2.965, 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 Pm $\overline{3}$m 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.

已发现Na _0.5 Bi _0.5 TiO ₃（NBT）及其掺杂钙钛矿作为无铅压电材料，以前是无铅压电材料，在中温固体氧化物燃料电池（SOFC）中具有潜在的应用前景。其中，Bi缺陷和B位掺杂Mg的钛酸铋钠（Na _0.5 Bi _0.49 Ti _0.98 Mg _0.02 O _2.965，NBTM）表现出显着的氧离子电导率。在这里，我们报告了使用高温原位对NBT和NBTM陶瓷进行的结构分析中子衍射（NPD），以了解镁掺杂对离子电导率和结构的影响。两种钙钛矿氧化物在〜400°C时都有两个连续的相变，从R 3 c到P 4 bm，从P 4 bm到Pm$\overline{3}$m在约600°C时。揭示了Bi缺乏和Mg替代对氧空位浓度和离子位移的影响。此外，制造了由Ag-NBTM阴极和Ni-NBTM阳极组成的NBTM支持的单电池，以评估其在中温SOFC中应用的可能性。NBTM的结构稳定性仍然是一个主要问题，阻碍了其在高温和还原气氛下的使用。