Research Projects

The effective utilization and management of electrical and thermal energies are essential to achieve carbon neutrality and sustainable development. However, nearly two-thirds of the primary energy utilization dissipated as heat into the atmosphere. Thermoelectric materials can recycle this waste heat into useful electricity and therefore are expected to play a critical role in future energy management. Thermoelectric energy conversion efficiency is primarily determined by the parameter called figure of merit (zT) which depends on the electrical conductivity, Seebeck coefficient and thermal conductivity of the material. Presently the state-of-the-art thermoelectric materials based on metal chalcogenides exhibit maximum zT approx. 2.5 – 3.0 with corresponding conversion efficiency approx. 12-15%. The major limiting factor of improving the efficiency arises from the mutually contradicted material parameters. In this project, we propose to use high-entropy alloying strategy to design high-performance thermoelectric materials. High-entropy alloys have been proven to be useful in improving mechanical properties such as tensile strength, fatigue resistance and corrosion resistance. They have also been recently used to enhance performance in catalysis, energy storage and solar PV applications. We propose that unique and unconventional properties arising from the high-entropy effects, slow diffusion and severe lattice distortion would be beneficial to improve thermoelectric performance. The slow diffusion process enriches the bulk matrix with multiscale microstructure which would be useful in scattering phonons of different length scale. Moreover, the severe local lattice distortion also enhances the phonon scattering. These two effects together are expected to drastically reduce the lattice thermal conductivity, which is essential to realize high thermoelectric performance. Moreover, entropy-driven stabilization of single-phase solid solutions and high-symmetry crystal phases are expected to enhance the Seebeck coefficient through increased band degeneracy. In this project, we will synthesize chalcogenide-based high-entropy alloys (e.g., (Sn/Ge/Pb)(Se/Te), (Cu/Ag)(In/Ga)Te2) through solid state reactions at high temperature. We will carefully characterize the structural and microstructural phases, and then we will measure the Seebeck coefficient, electrical conductivity and thermal conductivity in the 300 – 1000 K temperature range to determine the thermoelectric performance. We will investigate the correlation of electrical and thermal transport properties with microstructure and lattice dynamics to shed light on the structure-property relationship. The successful implementation of this project will lead to the development of many high-performance thermoelectric materials which can be further used for the development of thermoelectric modules that have wide applications from micro-electronics to large-scale energy harvesting in industrial sectors.