Shockwave Fabrication of High Performance Thermoelectrics

Thermoelectric (TE) generators have the advantages of no moving parts and flexibility in deployment but suffer from low heat to electricity conversion efficiencies, with a major loss component being conductive (phonon) heat transfer through the TE lattice. By using a high pressure shockwave consolidation, nanopowders can be fused into a solid bulk TE material while preserving the nanostructure. The high density of grain boundaries and lattice defects impedes phonon transport while allowing electron flow. Specific Phase 2 research thrusts will be directed at transitioning laboratory fabrication into volume manufacturing, at producing a graded thermoelectric that is optimized for different temperature ranges over the length of the element, and at preparing bulk thermoelectric material from transition metal trichalcogenides that are not appropriate for melt or powder sintered fabrication. The overall conversion efficiency of a TE device will always be limited by the Carnot ratio of (Th-Tc)/Th, where Th and Tc are the temperatures of the hot and cold junctions. With the restrictions on phonon transport accruing from nanopowder consolidation, conversion efficiencies in excess of 30% of the Carnot limit are reasonable.