Thermoelectric Materials with Potential High Power Factors for Electricity Generation

The thermoelectric figure of merit ZT of materials limits the performance of a thermoelectric power generator. To date, the main gains from the worldwide effort in either engineered bulk materials or low-dimensional systems have been mostly based on the strategies of reducing the thermal conductivity. We explore several bulk thermoelectric materials that have respectable mecha- nical strength and chemical stability at elevated temperatures for potential power generation. Our strategy is to first explore the avenue of significantly increasing the power factor (PF), then the avenue of lowering thermal conductivity, perhaps by nanocompositing. We examine the layered cobaltates with sharp resonant peaks in the electronic density of states near the Fermi energy level due to strong electron correlation. We suggest that electron correlation may be used as a new tuning parameter to significantly increase the PF. We also report that a substantial increase (over 30%) in PF can be achieved in filled skutterudites (such as p-type CeFe4Sb12) through nonequilibrium synthesis by rapid conversion of the amorphous materials made by the melt spinning to single-phase crystalline materials under pressure. This process, in conjunction with the rattling to lower the lattice thermal conductivity, could further enhance the ZT values of the filled skutterudites.