Panoscopic approach for high-performance Te-doped skutterudite

One-step plasma-activated sintering (OS-PAS) fabrication of single-phase high-performance CoSb3-based skutterudite thermoelectric material with a hierarchical structure on a time scale of a few minutes is first reported here. The formation mechanism of the CoSb3 phase and the effects of the current and pressure fields on the phase transformation and microstructure evolution are studied in the one-step PAS process. The application of the panoscopic approach to this system and its effect on the transport properties are investigated. The results show that the hierarchical structure forms during the formation of the skutterudite phase under the effects of both current and sintering pressure. The samples fabricated by the OS-PAS technique have defined hierarchical structures, which scatter phonons more intensely over a broader range of frequencies and significantly reduce the lattice thermal conductivity. High-performance bulk Te-doped skutterudite with the maximum ZT of 1.1 at 820 K for the composition CoSb2.875Te0.125 was obtained. Such high ZT values rival those obtained from single filled skutterudites. This newly developed OS-PAS technique enhances the thermoelectric performance, dramatically shortens the synthesis period and provides a facile method for obtaining hierarchical thermoelectric materials on a large scale. A one-step plasma activated sintering enables semiconductors to be rapidly fabricated with structures ideal for thermoelectric conversion. skutterudites are promising thermoelectric materials at temperatures suitable for energy harvesting, but they have trouble retaining heat. Xinfeng Tang from Wuhan University of Technology in China and colleagues have developed a ‘panoscopic’ approach that introduces a hierarchy of atomic, nanoscale, and mesoscale features into tellurium-doped skutterudites to better scatter the crystal vibrations, or phonons, that dissipate thermal energy. The team used electrically generated plasmas to activate the surfaces of powdery precursors and then formed high-quality bulk skutterudites in just a few minutes. X-ray and electron microscopy analysis showed the plasma-assisted sintering process induced hot spots into the crystal lattice, which could be controlled to yield a range of microstructures for phonon scattering. Compared with monotonous grain-size skutterudites, panoscopic approach for skutterudite synthesized by one-step-PAS technique possess lower lattice thermal conductivity and higher ZT.