10/26 Seminar Speech

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SpeakerProfessor Hsin-Jay Wu

OrganizationNational Chiao Tung University, Department of Materials Science and Engineering 

TopicPhase diagram engineering - A New Avenue Towards High Performance Thermoelectric Materials

 Date10:20 am 2020.10.26

LocationRoom 203, College of Engineering

Abstract;To cope with the global energy shortage and environmental concern, the development of green energy is urgent. The thermoelectric materials (TE) can convert waste heat into electricity via the Seebeck effect, which plays an important role in easing the energy issues. Nevertheless, there is still room for improvement when it comes to the conversion efficiency and thermal stability of a TE material and TE module. Herein, a new thermodynamic approach is adopted, which aims to depict the temperature-dependent solubility for a specific TE compound by a phase diagram. In other words, the phase diagram acts as a map guiding the composition and synthesis route for our TE materials, which allows us to rejuvenate and re-visit the well-established Bi2Te3-based, PbTe-based, GeTe-based, and Zn4Sb3-based TE materials. By determining the solubility range of certain dopants, including the Ag, Cu, In and Ga in the above-mentioned TE compounds, the TE properties can be optimized and the resultant figure-of-merit (ZT) is enhanced. For example, carrier optimization could be realized by adjusting the solubility content in Cu-Bi2Te3, Ga-PbTe and In- Zn4Sb3, which boost the power factor (PF = S2ρ-1). Meanwhile, the reduction in lattice thermal conductivity is attained by introducing multiple-scale of defects. Synergistically, the figure-of-merit for our n-type Ga-PbTe, n-type Cu-Bi2Te3 and p-type Sb-GeTe can be elevated to a record high value.