SPECIATION ANALYSIS APPLIED TO THE ELECTRODEPOSITION OF PRECURSORS OFNEODYMIUM CUPRATE AND RELATED PHASES - FIRST APPLICATION OF SPECIATION MODELING TO A SOLUTION NOT AT EQUILIBRIUM

We report the first time that speciation analyses have been used to ex plain the distribution of products obtained by a system not at equilib rium: films of insoluble metal hydroxide have been obtained by cathodi c electroprecipitation from aqueous solutions containing the nitrate s alts of Nd3+ and Cu2+. Variation in film composition is achieved by ma nipulating deposition parameters, such as deposition voltage V-a and s olution composition. The variations are caused by changes at the elect rode/solution interface and differences in the solution-and solid-phas e speciation characteristics of the two metals and their hydroxides. T he experimental compositions of the Nd-Cu hydroxides are correlated wi th thermodynamic formation constants beta, and with calculations of co ncentrations obtained using speciation analyses. The accuracy of the p redicted compositions is taken to verify the model of electroprecipita tion.