Vilupanur A. Ravi

Hardness and fracture toughness of thermoelectric La3−xTe4

Lanthanum telluride (La3−xTe4) is a state-of-the-art n-type high temperature thermoelectric material that behaves as a weak and brittle ceramic. Vickers microindentation hardness testing was explored as a rapid analysis technique to characterize the mechanical properties of this material. An indentation size effect was observed with hardness values ranging from 439xa0±xa031xa0kgf/mm2 (0.01xa0kgf/10xa0s contact time) to 335xa0±xa06xa0kgf/mm2 (0.5 kgf/10xa0s contact time). The Vickers indentation fracture toughness, KVIF, based on measurements of crack lengths emanating from the corners of the Vickers indents was 0.70xa0±xa00.06xa0MPaxa0m1/2.

Solidification processing of Te-Sb-Pb alloys for thermoelectric applications

A solidification processing approach to the refinement of lead-tellurium-antimony alloy microstructure is described. Liquid alloys with eutectic, hyper-eutectic and hypo-eutectic compositions (relative to lead) were cooled to the solid state in three distinct ways, i.e. by water quenching, air cooling and furnace cooling. The structures of the alloys resulting from the three different solidification paths were examined using electron microscopy and the micrographs were quantified. Classical solidification methods were used to interpret the structures in relation to the cooling histories.