Electrodeposition of Sb, Bi, Te, and their alloys in AlCl3-NaCl-KCl molten salt

The Electrochemistry of Sb, Bi, and Te in AlCl3-NaCl-KCl molten salt containing SbCl3, BiCl3, and/or TeCl4 at 423K was investigated by voltammetry, and electrodeposition of the three metals was performed under constant potential control in the melt. The voltammogram on a glassy carbon (GC) electrode in a melt containing 0.025moldm-3 [M] SbCl3 showed a couple of redox peak corresponding to the Sb/Sb(III) redox reaction, and a stable layer of pure Sb was deposited under the constant potential control. The voltammograms in the melt containing 0.025M BiCl3 or 0.025M TeCl4 showed several redox couples. Stable deposit layers of pure Bi and Te were not obtained under the constant potential control, as the deposited layers detached from the electrode and immediately dissolved into the molten salt. Binary alloy deposition was possible in a melt containing BiCl3 and SbCl3, and also with BiCl3 and TeCl4. A stable Bi-Sb alloy deposit of metallic Sb and Bi-Sb solid solution was obtained at 0.8 and 0.9V versus Al/Al(III) in the melt containing BiCl3 and SbCl3. The atomic ratio of Bi in the deposit was 37% at 0.9V and 57% at 0.8V. A stable Bi-Te alloy deposit was also obtained with the molten salt containing BiCl3 and TeCl4. The deposited Bi-Te alloy consisted of a mixture of Bi2Te3, BiTe, and Bi2Te. The alloy deposit had good crystallinity and the preferential orientation was the (110) plane.