The electrodeposition of tungsten has been investigated in the molten salt systems ZnBr2-NaBr-WBr5 and ZnCI2-NaC1-WC16 at 450~ Voltammetric results showed that the reduction of tungsten species is an irreversible process. Electrodeposits were mixtures of a-and ~-tungstens, the former being the thermodynamically stable phase, a-Tungsten exhibited the shape of cubic crystallites which tended to grow larger, whereas 13-tungsten always had a crystal size smaller than 1 ixm. The 13-tungsten was formed during the initial stage of electrodeposition, irrespective of the substrata material, and remained predominant at high current densities or in pulsed electrolysis. It is likely that the phase transition of 13-tungsten to a-tungsten occurs when the size of the [3-tungsten crystallites becomes larger than a critical value.
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