Junctions and Diffusion Barriers for High Temperature Thermoelectric Modules

Thermoelectric modules based on doped bismuth telluride (Bi2Te 3) are commonly used for the construction of thermoelectric generators (TEGs) and heat pumps. However, due to low operating temperature (< 200oC), TEGs based on this material reveal low efciency. In order to obtain high effectiveness in energy conversion, one needs to design high temperature modules made of new thermoelectric materials. The goal of the present work has been to develop the method of preparation of ohmic junctions between semiconducting CoSb3 element and metallic Cu electrode, for temperatures up to 600oC. In order to protect thermoelectric material from interaction with a solder and the electrode material, the appropriate diffusion barriers were applied. The junctions were formed by the resistance soldering technique in the protective atmosphere of Ar + H2. Lead-free alloys based on Ag and Cu were used as the solder. Diffusion layers of Ni were prepared via the magnetron sputtering technique. The chemical and microstructural properties of the junction area were analyzed by scanning electron microscope (SEM) equipped with EDX analyzer. Resistivity measurements and current-voltage characteristics were used to determine the contact resistance and ohmic contact quality