Electrodeposition of Iron Group-Rare Earth Alloys from Aqueous Media

Binary iron group (IG)-rare earth (RE) and ternary IG-RE-B alloys were codeposited from aqueous chloride and sulfamate solutions containing glycine as the complexing agent. The effects of solution composition and deposition conditions on deposit composition, coercivity, and morphology were investigated using dc and pulse current electrodeposition, resulting in nanocrystalline deposits approaching amorphism (grain size, ∼5 nm). Continuing research indicates substantially increased RE deposit contents have been achieved with modifications in solution composition and ratios of IG and RE to glycine with applied mA cm−2 and vigorous agitation; e.g., CoSm deposits containing 15-18 atom % Sm have been obtained. A mechanism for the codeposition of the alloys is proposed. It involves hetero-nuclear glycinato coordination complexes as a result of the zwitterionic characteristics of glycine. The complexes adsorbed on the cathode provide step-wise reduction of the depositing metals with surface adsorbed H atoms and/or direct electron transfer, resulting in alloy deposits. © 2004 The Electrochemical Society. All rights reserved.