CORROSION OF FERRITIC STAINLESS-STEEL DURING METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION GROWTH USING A FLUORINATED PRECURSOR

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