Microstructure and electrical properties of Mn1+xCo2−xO4 (0≤x≤1.5) spinels synthesized using EDTA-gel processes

Cobalt manganese spinels have recently been studied as potential candidates for protective-conducting coatings on ferritic stainless steel interconnects for Intermediate-Temperature Solid Oxide Fuel Cells (IT-SOFCs) applications. Mn1+xCo2−xO4 (x=0, 0.25, 0.5, 0.75, 1.0 and 1.5) spinels were synthesized using EDTA-gel processes to optimize the performance of high-quality spinel protective-conducting films developed on steel interconnects. The structure, morphology and the electrical conductivity of the obtained bulk samples were investigated using XRD, SEM and EIS, respectively. The obtained MnCo2O4 and Mn1.25Co1.75O4 oxides were cubic spinels over the whole temperature range (373≤T≤1073 K). The other samples exhibited both tetragonal and cubic structures with higher cubic phase content at increasing temperatures. The prepared Mn1+xCo2−xO4 (0≤x≤0.5) spinels exhibited desirable electrical conductivity; the highest conductivity at 1073 K was found for MnCo2O4 (132.2 S cm−1), whereas the lowest one (1.9 S cm−1) for Mn2.5Co0.5O4. Tetragonal-cubic phase transition depended on spinel composition, and its influence on the electrical properties of the spinel solid solutions was studied over a wide temperature range.