Preparation and Characterization of CuxFe3-xO4 (0.75≤x≤1.25) Spinels for Use as Stainless Steel Interconnect Coatings in Intermediate Temperature Solid Oxide Fuel Cells

In this study, we prepared nano-crystalline spinel powders of CuxFe3-xO4 (0.75≤x≤1.25) using an optimized glycine–nitrate process followed by calcination. The objective was to evaluate their potential as coatings for stainless steel interconnects in intermediate temperature solid oxide fuel cells (IT-SOFCs). The synthesized spinels were characterized using X-ray diffraction, thermal gravimetric and differential thermal analysis, scanning and transmission electron microscopy, and other techniques. We explored different glycine to nitrate ratios and calcination temperatures, finding that a ratio of 2 facilitated the formation of single-phase copper ferrite. Electrical conductivity measurements identified stoichiometric CuFe2O4 as having the highest conductivity, attributed to a change from p-type to n-type conductivity. Furthermore, the spinel demonstrated thermal stability and a crystallite growth behavior consistent with the parabolic grain growth law, with an activation energy of 363±15 kJ/mol. The coefficient of thermal expansion was measured at 11×10^-6 °C^-1. Compatibility tests with cathodic materials affirmed chemical stability at 800 °C.