Synthesis and characterization of nanostructured Cux (Mn۱.۵-x/۲Co۱.۵-x/۲)O۴ as an interconnect coating for solid oxide fuel cell

Manganese-Cobalt Oxide (MCO) spinel oxide is a promising composition as a protective coating for the metallic interconnects of a SOFC. In an effort to reach better properties, such as suitable thermal expansion match, good electrical conductivity, and fine structural stability, various elements have been doped in the spinel structure. In this study, the effect of Cu addition as a dopant on the electrical properties of MCO spinel is investigated. Powders with a nominal composition Cux(Mn۱.۵-x/۲Co۱.۵-x/۲)O۴ (x=۰, ۰.۱۵, and ۰.۳) were successfully synthesized based on the sol-gel Pechini method. The phase composition and microstructure of the synthesized powder were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The XRD results revealed that a pure phase with a spinel structure was obtained for different amounts of doped samples. The microstructural characteristics of the synthesized powders revealed that the average particle size of the powder decreased from about ۸۴nm to ۵۲nm with the introduction of Cu. To evaluate the effect of Cu on the sintering behavior of MCO, the powder was pressed and sintered at ۱۲۰۰°C for ۲h. The density measurement and FESEM results showed that the addition of Cu promotes the sintering mechanism, and the density was improved. In addition, the electrical properties of the samples were evaluated using the ۲probe direct current technique at different temperatures. The results revealed that the addition of ۰.۳ Cu increased the electrical conductivity of the sample from ۰.۱۰۲ to ۰.۲۱۸ S.cm-۱ at ۸۰۰°C. This significant improvement can be attributed to the promotion of sintering and also facilitating electron flow by substitution of Cu+۲ cations in the spinel structure.