Thermal and electronic charge transport in bulk nanostructured Zr0.25Hf0.75NiSn composites with full-Heusler inclusions

Pierre Ferdinand P. Poudeu

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ppoudeup@umich.edu

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Julien PA Makongo, Dinesh K Misra, James R Salvador, Nathan J Takas, Guoyu Wang, Michael R Shabetai, Aditya Pant, Pravin Paudel, Ctirad Uher, Kevin L Stokes, and Pierre FP Poudeu (2011)

Journal of Solid State Chemistry, 184(11):2948-2960.

Bulk Zr0.25Hf0.75NiSn half-Heusler (HH) nanocomposites containing various mole fractions of full-Heusler (FH) inclusions were prepared by solid state reaction of pre-synthesized HH alloy with elemental Ni at 1073 K. The microstructures of spark plasma sintered specimens of the HH/FH nanocomposites were investigated using transmission electron microscopy and their thermoelectric properties were measured from 300 K to 775 K. The formation of coherent FH inclusions into the HH matrix arises from solid-state Ni diffusion into vacant sites of the HH structure. HH(1-y)/FH(y) composites with mole fraction of FH inclusions below the percolation threshold, y similar to 0.2, show increased electrical conductivity, reduced Seebeck coefficient and increased total thermal conductivity arising from gradual increase in the carrier concentration for composites. A drastic reduction (similar to 55%) in kappa(1) was observed for the composite with y=0.6 and is attributed to enhanced phonon scattering due to mass fluctuations between FH and HH, and high density of HH/FH interfaces. (C) 2011 Elsevier Inc. All rights reserved.

Times Cited: 23

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