Synthesis and characterization of nanostructured Cux (Mn1.5-x/2Co1.5-x/2)O4 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(Mn1.5-x/2Co1.5-x/2)O4 (x=0, 0.15, and 0.3) 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 84nm to 52nm with the introduction of Cu. To evaluate the effect of Cu on the sintering behavior of MCO, the powder was pressed and sintered at 1200°C for 2h. 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 2probe direct current technique at different temperatures. The results revealed that the addition of 0.3 Cu increased the electrical conductivity of the sample from 0.102 to 0.218 S.cm-1 at 800°C. This significant improvement can be attributed to the promotion of sintering and also facilitating electron flow by substitution of Cu+2 cations in the spinel structure.