Crystal structure and morphology of electrodeposited zinc-iron binary alloys
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Deposits of zinc-iron alloy have been prepared galvanostatically from a sulphate bath and the crystal structure has been determined by X-ray diffraction and transmission electron microscopy measurements. The electrodeposited zinc-iron alloys have metastable structures and the individual phases coexist over wide composition ranges. The phases are identified as η(100∼73 at % zinc), Γ(87∼48 at % zinc), Γ1(78∼62 at % zinc) and α(62∼0 at % zinc). Thec andc/a in the h.c.p. lattice of the η-phase decrease continuously with decrease of zinc concentrations, and the latter changes from 1.86 to 1.60 (a andc are the lattice constants of the η-phase in the direction of thea- andc-axes, respectively). The η-phase particles exhibit a hexagonal plate-like morphology which is thin in the direction of thec-axis. The morphology of the electrodeposits changes from plate-like to pyramidal shape when fine η-phase particles (∼100 nm) start to form surrounding the η-phase platelets, and then to lenticular or granular in the Γ/Γ1 duplex region. The α-phase forms in the low zinc concentration region and changes the electrodeposits to a fine cuboidal morphology.
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