Electrodeposition of Bi₂Te₃ films

The Bi₂Te₃ and its derivative compounds are very interesting materials in the field of thermoelectric refrigeration at room temperature. An electrochemical deposition that is an alternative process of the standard synthesis is developed in our laboratory. The study of the reduction of Te^IV+ and Bi^III+ and their mixtures, in aqueous solvent, evidences the direct formation of near stoichiometric Bi₂Te₃ compounds. The electrodeposition is performed according to the reaction: 2BiO⁺+3HTeO⁺₂+13H⁺+18e⁻→Bi₂Te₃↓+8H₂OThe synthesis is realized in an acid electrolyte (HNO₃1M), allowing the stability of Te^IV+ and Bi^III+ salts. The Bi/Te ratio in the electroformatted films is varying with the solution composition and the applied current density. The X‐ray controls of all the compounds obtained by this method show only one product, with a good crystallinity. The patterns are consistent with the space group R‐3m of Bi₂Te₃. However, it should be noted orientation effects. The films exhibit qualitative thermoelectric properties of as n‐type semiconductor.