Interactions between (Mn,Co)3O4 SOFC Interconnect Coating Materials and Chromia

Manganese cobalt oxides are promising coating materials for reducing chromium volatilization, and thus the associated cathode poisoning, from interconnect alloys in solid oxide fuel cells (SOFCs). Interaction between this coating and the oxide scale formed on the alloy during fuel cell operation can lead to changes in the coating composition and thus its performance. In this paper, the reaction between manganese cobalt spinet oxides and chromia is described. The reaction product consists of two layers. The layer in contact with chromia has two chromium ions per formula unit, i.e. (Mn,Co)Cr2O4, and grows by the diffusion of cobalt and manganese from (Mn,Co)(3)O-4. In addition, chromium dissolves into (Mn,Co)(3)O-4, which results in a second reaction layer. Both layers form the spinet structure, but there is a distinct difference between the growth mechanisms. The relative growth rates of these two layers depend on temperature, so the dominant mechanism also changes with temperature.