Microstructure and Thermoelectric Properties of Mechanically Alloyed Zr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01/WO3 Half-Heusler Composites

Pierre Ferdinand P. Poudeu

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ppoudeup@umich.edu

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Dinesh K Misra, Julien PA Makongo, Pranati Sahoo, Michael R Shabetai, Pravin Paudel, Kevin L Stokes, and Pierre FP Poudeu (2011)

Science of Advanced Materials, 3(4):607-614.

Bulk Zr0.50Hf0.50Ni0.8Pd0.2Sn0.99Sb0.01 half-Heusler (HH) alloys containing various concentrations of WO3 inclusions were prepared using a combination of mechanical alloying and hot pressing. The microstructures of hot pressed pellets of the synthesized composites were investigated using transmission electron microscopy (TEM) and their thermal and electronic transport properties were measured from 300 K to 750 K. The electrical conductivities of the synthesized composites containing low concentrations (up to 5 wt%) of WO3 inclusions is slightly lower than that of the bulk matrix. Increasing the concentration of WO3 to 10 wt% results in a large increase (30%) in the electrical conductivity. The thermopower slightly decreases with increasing concentrations of WO3 inclusions up to 5 wt% and drastically drops (33%) for the composite with 10 wt% WO3 inclusions. Using electron microscopy and powder X-ray diffraction data, we attribute the observed large increase in the electrical conductivity and drastic decrease of the thermopower for the composite with 10 wt% WO3 to the formation of highly conductive ZrxWO3 inclusions within the matrix arising from partial reaction between the WO3 and the HH matrix. The lattice thermal conductivity of the composites increases with increasing WO3 content, presumably due to the formation of interconnected precipitates of thermally conductive ZrxWO3 and HfO2 phases within the HH matrix.

Times Cited: 8 Si

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