Study of the purification of Gd by electrorefining

Gadolinium metal can be prepared 99.98 percent pure by the calcium reduction of GdF3 if (1) the reactants are highly purified, (2) the reactants and products are handled under inert conditions, and (3) the metal is vacuum melted at high temperatures followed by distillation. Since the process is costly in time and materials, an alternate method which would involve the electro-purification of crude gadolinium was studied. The electrolyte studied was LiCl:LiF:GdF3. The best results were obtained using a 77.6 wt. percent LiCl, 11.2 wt. percent LiF, 11.2 wt. percent GdF3 electrolyte at 7000C. It was shown that the purity of the deposit was strongly dependent on the purity of the electrolyte and the temperature. The purest deposit of Gd was obtained when the LiCl and LiF were purified by distillation and high purity GdF3 was used. The effect of various methods used to remove the adhering electrolyte salts and to consolidate the deposited dendrites was studied. Removal of the adhering salts by distillation followed by arc melting of the dendrites gave the purest Gd. The analyses of the metal prepared under the various conditions are given