Issues and opportunities from Peltier effect in functionally-graded colusites: From SPS temperature modeling to enhanced thermoelectric performances

Abstract The quaternary sulphide V-Sn colusite, Cu26V2Sn6S32, is one of the most promising cost-efficient thermoelectric materials to date because of the low toxicity, wide availability and low cost of the composing elements. Recent studies have demonstrated the potential of this environmentally-friendly material and its transport properties are now well understood. In the present work, we take the next step of producing large quantities of optimised V-Sn colusite using industrial-grade precursors and investigating the effect of Spark Plasma Sintering (SPS) in the production of large cylindrical pucks of up to 30 mm in diameter and 10 mm in thickness. In the process, we identified and solved several key issues including the generation of temperature gradients during SPS, porosity and defect formation. The generation of radial and axial temperature gradients within the sample during SPS has been modeled using modified Fourier and Ohm laws and confirmed experimentally thanks to the TSPS-dependent transport properties of V-Sn colusite and EDS analysis. We demonstrate that large pucks of colusite with enhanced thermoelectric properties can be produced using a combination of SPS and High-temperature Isostatic Press (HIP). Overall, our work experimentally and theoretically demonstrates that the production of both homogeneous and functionally-graded bulk materials can be easily up-scaled through a careful control of the SPS conditions.