Enhanced thermoelectric figure-of-merit in spark plasma sintered nanostructured n-type SiGe alloys

We report a significant enhancement in the thermoelectric figure-of-merit of phosphorous doped nanostructured n-type Si80Ge20 alloys, which were synthesized employing high energy ball milling followed by rapid-heating using spark plasma sintering. The rapid-heating rates, used in spark plasma sintering, allow the achievement of near-theoretical density in the sintered alloys, while retaining the nanostructural features introduced by ball-milling. The nanostructured alloys display a low thermal conductivity (2.3W/mK) and a high value of Seebeck coefficient (-290 mu V/K) resulting in a significant enhancement in ZT to about 1.5 at 900 degrees C, which is so far the highest reported value for n-type Si80Ge20 alloys. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768297]