Cation distribution in spinel (Mn,Co,Cr)3O4at room temperature

As part of a study of the long-term operation of solid-oxide fuel cells, three (Mn,Co,Cr)3O4 samples have been synthesized and characterized. X-ray and neutron diffraction patterns from the powder samples at room temperature were measured and the data were co-refined. The neutron data were indispensible in locating Mn, Co and Cr within the crystallographic unit cell with their respective atomic occupancies. Two of these samples have been identified as cubic Mn0.76Co0.58Cr1.66O4 and Mn1.28Co1.72O4. The third is a two-phase sample containing cubic Mn1.66Co1.34O4 and tetragonal Mn2.05Co0.91O4 in a 59.1 (6):40.9 (6)% mass fraction ratio. Cr, which might be introduced from reaction with chromia during oxidation of interconnect materials, exhibits a preference for the octahedral site rather than the tetrahedral site. Without Cr, Mn dominates the octahedral site.