Thermal and electronic charge transport in bulk nanostructured Zr{sub 0.25}Hf{sub 0.75}NiSn composites with full-Heusler inclusions

Journal Article · Tue Nov 15 00:00:00 EST 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.08.036· OSTI ID:21580061

Makongo, Julien P.A.; Misra, Dinesh K ^[1]; Salvador, James R ^[2]; Takas, Nathan J ^[1]; Wang, Guoyu ^[3]; Shabetai, Michael R; Pant, Aditya; Paudel, Pravin ^[1]; Uher, Ctirad ^[3]; Stokes, Kevin L ^[1]

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1. Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148 (United States)
2. Chemical Sciences and Materials Systems Laboratory, General Motors R and D Center, Warren, MI 48090 (United States)
3. Department of Physics, University of Michigan, Ann Arbor, MI 48109 (United States)

Bulk Zr{sub 0.25}Hf{sub 075}NiSn 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{approx}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 ({approx}55%) in {kappa}{sub l} 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. - Graphical abstract: Large reduction in the lattice thermal conductivity of bulk nanostructured half-Heusler/full-Heusler (Zr{sub 0.25}Hf{sub 075}NiSn/ Zr{sub 0.25}Hf{sub 075}Ni{sub 2}Sn) composites, obtained by solid-state diffusion at 1073 K of elemental Ni into vacant sites of the half-Heusler structure, arising from the formation of regions of spinodally decomposed HH and FH phases with a spatial composition modulation of {approx}2 nm. Highlights: > Bulk composites from solid state transformation of half-Heusler matrix through Ni diffusion. > Formation of coherent phase boundaries between half-Heusler matrix and full-Heusler inclusion. > Alteration of thermal and electronic transports with increasing full-Heusler inclusion. > Enhanced phonon scattering at half-Heusler/ full-Heusler phase boundaries.

• OSTI ID: 21580061
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 11; Other Information: DOI: 10.1016/j.jssc.2011.08.036; PII: S0022-4596(11)00476-2; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALLOYS
CHARGE TRANSPORT
COMPOSITE MATERIALS
DECOMPOSITION
ELECTRIC CONDUCTIVITY
INCLUSIONS
MICROSTRUCTURE
NANOSTRUCTURES
PHONONS
SCATTERING
SOLIDS
THERMAL CONDUCTIVITY
THERMOELECTRIC PROPERTIES
TRANSMISSION ELECTRON MICROSCOPY
CHEMICAL REACTIONS
ELECTRICAL PROPERTIES
ELECTRON MICROSCOPY
MATERIALS
MICROSCOPY
PHYSICAL PROPERTIES
QUASI PARTICLES
THERMODYNAMIC PROPERTIES