Severe Plastic Deformation, A Tool to Enhance Thermoelectric Performance

Abstract

High pressure torsion (HPT) is one of the methods introducing severe plastic deformation (SPD). Particularly HPT has been applied to skutterudites and has shown to be a valuable and efficient technique for grain refinement in the nanometer regime via increasing the concentration of point defects, dislocations and high-angle grain boundaries. These microstructural changes significantly enhance phonon scattering. The decrease of crystallite size causes enhanced microhardness, i.e. Hall-Petch strengthening applies. For a thermoelectric material HPT may slightly enhance the Seebeck coefficient and electrical resistivity, but significantly decreases thermal conductivity and concomitantly increases ZT. The article intends to give a comprehensive view on all data available on the influence of the various techniques of severe plastic deformation on thermoelectric materials in general.