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Article Dans Une Revue Electrochimica Acta Année : 2002

Electrodeposition processes of tantalum(V) species in molten fluorides containing oxide ions

Résumé

The influence of the molar ratio O/Ta noted Ro on the electrodeposition of tantalum in molten fluorides at 800°C is examined. After additions of both K2TaF7 and Na2O , we observed: (i) tantalum deposit is obtained only by reduction of TaF72-; (ii) the oxide ions react with TaF72- to give oxifluoride species, identified first as TaOF52- and for higher oxide content, as TaO2F43-; (iii) the electroreduction of TaOF52- leads to the formation of an unstable bivalent tantalum species (TaO); (iv) the conversion of TaF72- to oxifluoride is complete when Ro is one. Titration of Ta by ICP and oxygen by a carbothermal-reduction technique show that for Ro >1, insoluble compounds Na3TaO4 and NaTaO3 are formed. For Ro > 3, these species seem to be solubilised. Electrodeposition runs on copper cathodes show that pure and coherent Ta coatings are obtained for a lower oxide content (Ro<0.5). For higher Ro, the faradic efficiencies are low. The coatings are powdery and include the presence of Na3TaO4, NaTaO3 and traces of Ta metal, arising from the decomposition of TaO.

Dates et versions

hal-03998783 , version 1 (21-02-2023)

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Pierre Chamelot, Patrice Palau, Laurent Massot, André Savall, Pierre Taxil. Electrodeposition processes of tantalum(V) species in molten fluorides containing oxide ions. Electrochimica Acta, 2002, 47 (21), pp.3423-3429. ⟨10.1016/S0013-4686(02)00278-5⟩. ⟨hal-03998783⟩
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