Preparation and properties of Mn_(1.5-0.5x)Co_(1.5-0.5x)Cu_xO_4 spinel powders and coatings

Mn1.5-0.5xCo1.5-0.5xCuxO4(x =0,0.1,0.2,0.3 and 0.4,which is the mole fraction of Cu) spinel powders were prepared by sol-gel method,and applied onto the surface of SUS 430 alloy via a slurry dip-coating and subsequent sintering process.Infulence of Cu on crystal stucture,thermal expansion behavior and high-temperature conductivity were investigated,the anti-oxidation of Mn1.35Co1.35Cu0.3O4 coating was tested.The results show that,with increasing Cu concentration,phase structure changes from cubic/tetragonal phases to single cubic phase.When x=0,the spinel composes of cubic/tetragonal phases,while pure cubic phase presents at x≥0.2.The cofficient of thermal expansion(CTE) increases with increasing Cu doping content and the otherwise decrease of CTE at 500 ℃ is prevented.The CTE of Mn1.35Co1.35Cu0.3O4 spinel coating can be compatible well with that of SUS 430 alloy in the range of 30~ 800 ℃(the average CTE is 12.45×10-6 and 12×10-6~12.4×10-6 K-1 respectively).Moreover,the high temperature conductivity increases with increasing Cu doping content.All of the spinel's conductivities are over 1.3 S-cm-1 at 800 ℃,meeting the interconnects electrical conductivity criteria.The oxidation rate of SUS 430 alloy coated Mn1.35Co1.35Cu0.3O4 can decrease by 87.5% at 800 ℃.So SUS 430 coated with Mn1.35Co1.35Cu0.3O4 can be used as interconnects of solid oxide fuel cell(SOFC).