Corrosion of ferritic stainless steel during metal-organic chemical vapour deposition growth using a fluorinated precursor

The growth of Ce1-xGdxO2-x/2 films, which are of interest as electrolytes in solid oxide fuel cells, by metal-organic chemical vapour deposition has been studied. The precursors [{Ce(fod)(3)}(2)(tetraglyme)] and [{Gd(tmhd)(3)}(2)(tetraglyme)] (where fod-H is 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dione, tmhd-H is 2,2,6,6-tetramethyl-3,5-heptanedione and tetraglyme is tetraethylene glycol dimethyl ether) have been used. Type 430 ferritic stainless steel was used as the substrate. Although the overlayer thickness appeared to be substantial, cross-sectional analysis revealed an intermediate oxide layer had formed. This paper details the experimental work used to ascertain the conditions that caused oxidation. A corrosion mechanism based on existing theories is presented. Halogenated precursors may be incompatible with alloy metal substrates. (C) 1997 Elsevier Science Ltd.