Abstract
Thermoelectric power generation that converts thermal energy into electrical energy has been considered to be a promising green technology. Bismuth telluride based compounds have reasonably high thermoelectric figure-of-merit at room temperature regime. They have been widely employed in the applications of waste-heat recovery and thermoelectric refrigeration. If the thermoelectric properties of bismuth telluride compounds can be improved further, it would possible to increase the conversion efficiency of thermoelectric devices and contribute to the reduction of CO2 emission. In the study, bismuth telluride based raw materials are provided by the China Steel Corporation. Three different processing methods including zone-melting, cold press and hot press were used to prepare the Bi-Sb-Te compounds. The microstructure and thermoelectric transport properties of these materials with different doping processes are investigated. The samples prepared by zone melting and cold-press with hand-crushed powders have shown preferred crystallographic texture, while those by hot-press and cold press with ball-milled powders have no preferred texture. The anisotropic crystallographic texture leads to anisotropic transport properties. In addition, the samples with special Ag and Cu doping profiles have shown an unusual thermoelectric effect measured by a home-made scanning Seebeck system. The results suggest that it is possible to change the transport properties of Bi-Sb-Te based compounds through special fabrication process. The diffusion and thermoelectric properties of Bi-Sb-Te compounds with different fabrication processes are discussed in this research.