The effects of doping and processing on the thermoelectric properties of platinum diantimonide based materials for cryogenic Peltier cooling applications

The study of thermoelectrics is nearly two centuries old. In that time a large number of applicationshave been discovered for these materials which are capable of transforming thermalenergy into electricity or using electrical work to create a thermal gradient. Current use ofthermoelectric materials is in very niche applications with contemporary focus being upontheir capability to recover waste heat. A relatively undeveloped region for thermoelectricapplication is focused upon Peltier cooling at low temperatures. Materials based on bismuthtelluride semiconductors have been the gold standard for close to room temperature applicationsfor over sixty years. For applications below room temperature, semiconductors basedon bismuth antimony reign supreme with few other possible materials.The cause of this diculty in developing new, higher performing materials is due tothe interplay of the thermoelectric properties of these materials. The Seebeck coecient,which characterizes the phenomenon of the conversion of heat to electricity, the electricalconductivity, and the thermal conductivity are all interconnected properties of a materialwhich must be optimized to generate a high performance thermoelectric material. While forabove room temperature applications many advancements have been made in the creationof highly ecient thermoelectric materials, the below room temperature regime has beenstymied by ill-suited properties, low operating temperatures, and a lack of research.The focus of this work has been to investigate and optimize the thermoelectric propertiesof platinum diantimonide, PtSb2, a nearly zero gap semiconductor. The electronic propertiesof PtSb2 are very favorable for cryogenic Peltier applications, as it exhibits good conductivityand large Seebeck coecient below 200 K. It is shown that both n- and p-type dopingmay be applied to this compound to further improve its electronic properties. Throughboth solid solution formation and processing techniques, the thermal conductivity may bereduced in order to increase the thermoelectric gure of merit. Further reduction in thermalconductivity using other novel approaches is identied as an area of promising future research.Continued development of this material has the potential to generate a suitable replacementfor some low temperature applications, but will certainly further scientic knowledge andunderstanding of the optimization of thermoelectric materials in this temperature regime.