Valence Variability Induced in SrMoO₃ Perovskite by Mn Doping: Evaluation of a New Family of Anodes for Solid-Oxide Fuel Cells

We report on a series of SrMo1-xMnxO3-δ perovskite oxides designed as potential anode materials for solid oxide fuel cells (SOFCs). These materials were synthesized using a citrate method, yielding scheelite-type precursors with nominal SrMo1-xMnxO4 compositions, which were further reduced to obtain the active perovskite oxides. Their structural evolution was examined through X-ray diffraction (XRD) and neutron powder diffraction (NPD). These techniques provided insights into the crystallographic changes upon Mn doping, revealing key factors influencing ionic conductivity. Whereas the oxidized scheelite precursors are tetragonal, space group I41/a, the reduced perovskite specimens are cubic, space group Pm-3m, and show the conspicuous absence of oxygen vacancies, even at the highest temperature of 800ºC. The transport properties were analyzed through electrical conductivity measurements, exhibiting a metallic-like behavior. Thermogravimetric analysis (TGA) and dilatometry give insights into the thermal stability and expansion behavior, essential for SOFC operation. Test single SOFC were built in an electrolyte-supported configuration, on LSGM pellets of 300m thickness, assessing the performance of the title materials as anodes. This work emphasizes the critical relationship between the crystal structure and its electrochemical behavior, providing a deeper understanding of how doping strategies can optimize fuel cell performance.