Metal and mixed-metal (oxy)-hydroxide ceramic precursor materials prepared by cathodically-induced precipitation using a hydrogen-sorbing palladium electrode

The electrochemical reduction of several metal and mixed-metal sulfate aqueous solutions at a palladium electrode has been studied. For magnesium, lanthanum, yttrium and scandium sulfates, metal (oxy)-hydroxide films are produced by cathodically-induced precipitation of the metal cations, following the local generation of hydroxide ions at the hydrogen-sorbing cathode. Mixed-metal (oxy)-hydroxide films are prepared from yttrium/lanthanum and yttrium/scandium sulfate solutions. For mixed yttrium/indium sulfate solutions, the amorphous yttrium/indium (oxy)-hydroxide films initially contain indium dendrites. On calcination, a metastable yttrium/indium oxide phase is observed between 600-1000 °C, followed by the separation of the indium and yttrium oxides above 1000 °C. No films are accessible from the sulfate solutions of electropositive metals such as sodium and potassium, where the corresponding metal oxides and hydroxides are highly soluble. Metals are electrodeposited from separate sulfate solutions of zinc, nickel and indium, in preference to the cathodically-induced precipitation of the metal (oxy)-hydroxide.