Thermoelectric (TE) power generation, which offers potential for converting waste industrial heat into useful electricity, is foreseen to become increasingly important in the near future because of the need for alternative energy sources. How big this role is likely to be depends not only on the efficiency of TE materials but also on the crustal abundance and toxicity of their raw materials. BiSbTe intermetallic compounds, PbTe and SiGe alloys have served as the most widely used TE materials in the past half century. However, the key constituent elements, such as Te (0.001 ppm by weight), Sb (0.2 ppm), and Ge (1.4 ppm) are rare in the Earth’s crust, and Te and Pb are toxic. In this project, TE sulphides operating in the medium temperature ranges, instead of tellurides are chosen as the research starting point to explore TE materials with high figure of merit zT, which requires higher Seebeck coefficient, higher electrical conductivity, and lower thermal conductivity. A combination of band structure engineering and nanostructuring will be simultaneously investigated as an effective approach for improving TE performance. We will identify promising optimized compositions and sinter powders by Spark Plasma Sintering (SPS) to produce three kinds of TE metal (Cu, Bi, Ti) sulphides. Also, grain size and morphology controllable bulk nanomaterials will be fabricated by nonequilibrium routes, for example, melt spinning or mechanical alloying followed by SPS. The main objective of this work is to develop high performance nanostructured TE sulphides and modules to replace current commercial materials that use costly, scarce and toxic elements. Moreover, this project will help to clarify the physical mechanisms behinds the two strategies, band structure engineering and nanostructuring. The effect of thermodynamic process of the nonequilibrium preparation route on the electrical and thermal properties will be studied and the mechanisms involved will be established.
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