ELECTROCHEMICAL FORMATION OF NI-Y INTERMETALLIC COMPOUND LAYER IN MOLTEN CHLORIDE

The reduction of Y(III) ions in molten chloride is known to be a one-s tep three electron reaction [1, 2, 3], but a voltammogram of YCl3 in m olten LiCl-KCl-NaCl at a nickel electrode shows at least two reduction peaks of Y(III) ions, indicating the possibility of formation of Ni-Y intermetallic compounds. Using a galvanostatic electrolysis method, s amples were prepared at several current densities at 450, 500, 600 and 700-degrees-C, respectively, and were identified with X-ray diffracti on (XRD) and electron probe microanalysis (EPMA) methods. The results show that Ni2Y, Ni2Y3 and NiY can be produced by electrolysis and Ni2Y is found to be the predominant Ni-Y intermetallic compound under the experimental conditions. Nickel appears to diffuse in Ni2Y faster than yttrium, and the diffusion process is the rate determining step durin g Ni2Y formation.