Use of a Soluble Anode in Electrodeposition of Thick Bismuth Telluride Layers

Abstract

Integration of thermoelectric devices within an automotive heat exchanger could enable conversion of lost heat into electrical energy, contributing to improved total output from the engine. For this purpose, synthesis of thick bismuth telluride (Bi₂Te₃) films is required. Bismuth telluride has been produced by an electrochemical method in nitric acid with a sacrificial bismuth telluride anode as the source of cations. The binary layer grows on the working electrode while the counter-electrode, a Bi₂Te₃ disk obtained by high frequency melting, is oxidized to Bi^III and Te^IV. This process leads to auto-regeneration of the solution without modification of its composition. The thickness of films deposited by use of the Bi₂Te₃ anode was approximately 10 times that without. To demonstrate the utility of a soluble anode in electrochemical deposition, we report characterization of the composition and morphology of the films obtained under different experimental conditions. Perfectly dense and regular Bi₂Te₃ films (∼400 μm) with low internal stress and uniform composition across the cross-section were prepared. Their thermoelectric properties were assessed.