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

Abstract

As part of a study of the long-term operation of solid-oxide fuel cells, three (Mn,Co,Cr) 3 O 4 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 Mn 0.76 Co 0.58 Cr 1.66 O 4 and Mn 1.28 Co 1.72 O 4 . The third is a two-phase sample containing cubic Mn 1.66 Co 1.34 O 4 and tetragonal Mn 2.05 Co 0.91 O 4 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.