There have been few demonstrations that grain boundary engineering results in higher power generation efficiencies despite serious interest in using the strategy to improve zT. Using both Yb2O3 nanoprecipitates that decorate grain boundaries and carbon nanotubes to further reduce thermal conductivity and improve mechanical strength, a maximum zT of 1.43 at 875 K and a device ZT of approximately 1.0 in Yb-filled CoSb3-based nanocomposites are achieved. The preparation procedure of these materials is repeatable in mass production. Thermoelectric power generation modules based on these high-performance materials demonstrate a thermoelectric conversion efficiency of 9.3% under a temperature difference of 558 K. The results highlight nanostructured grain boundary engineering as a strategy to improve conventional thermoelectric materials, and the realistic prospect of large-scale thermoelectric power generation using skutterudite-based nanocomposites is demonstrated.
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