High pressure torsion, a large‐scale manufacturing tool for high ZT skutterudite thermoelectrics

Abstract

AbstractFor mass production of thermoelectric generators, a cheap/sustainable method is required to fabricate leg material with a high figure of merit, ZT. Severe plastic deformation, SPD, increases the defect density, and in parallel decreases the grains to nano‐size. SPD via high‐pressure torsion, HPT, was used to process hot pressed discs, whereby the Seebeck coefficient remained unchanged and the enhanced electrical resistivity was overcompensated by a low thermal conductivity, resulting in a raise of ZT. Secondly, cold pressed commercial p‐ and n‐type skutterudite‐powder was deformed via HPT, exhibiting higher ZT values than the hot‐pressed reference samples. This method was upscaled to samples of 30 mm diameter (heights: 1 mm, 8 mm). These large samples, enabled to study the influence of shear strain with all its impact on micro‐structural, physical and mechanical properties, revealing for the thin samples record high ZTs. Both thick samples showed homogeneous properties and ZTs∼1.3.