Mechanical properties and microstructure of spark plasma sintered nanostructured p-type SiGe thermoelectric alloys

SiGe based thermoelectric (TE) materials have been employed for the past four decades for power generation in radio-isotope thermoelectric generators (RTG). Recently nanostructuring has resulted in significantly increasing the figure-of-merit (ZT) of both n and p-type of SiGe and thus nanostructured Si80Ge20 alloys are evolving as a potential replacement for their conventional bulk counterparts in designing efficient RTGs. However, apart from Zr, their mechanical properties are equally important for the long term reliability of their TE modules. Thus, we report the mechanical properties of p-type nanostructured Si80Ge20 alloys, which were synthesized employing spark plasma sintering of mechanically alloyed nanopowders of its constituent elements with 12% boron doping. Nanostructured p-type Si80Ge20 alloys exhibited a hardness of similar to 9 +/- 0.1 GPa, an elastic modulus of similar to 135 +/- 1.9 GPa, a compressive strength of 108 +/- 02 MPa, and fracture toughness of similar to 1.66 +/- 0.04 MPalm with a thermal shock resistance value of 391 +/- 21 Wm(-1). This combination of good mechanical properties coupled with higher reported Zr of nanostructured p-type Si80Ge20 alloys are rendered to be a potential material for power generation applications, compared to its bulk counterpart. (C) 2015 Elsevier Ltd. All rights reserved.