Title: Multi-scale study of the deformation mechanisms of thermoelectric p-type half-Heusler Hf_0.44 Zr_0.44 Ti_0.12 CoSb_0.8 Sn_0.2

Abstract

Increasing the figure of merit ZT of thermoelectric (TE) alloys is a challenge that is currently attempted through various metallurgy methods, including nanostructuring and dislocation engineering. Microstructures with such a level of complexity raise questions about the mechanical reliability of these new materials. Indeed, despite the values of hardness and elastic modulus known for the clear majority of TE materials, the data on deformation mechanisms are still rare. Focusing on the nanostructured p-type half-Heusler Hf_0.44Zr_0.44Ti_0.12CoSb_0.8Sn_0.2, our multi-scale study aims to analyze the deformation mechanisms. Experiments conducted at macro-, meso-, and micro-scale are designed to trigger and assess plasticity mechanisms. Compression testing on bulk samples subject to a confining pressure environment and temperature leads to an exclusive brittle failure. The mixed-mode failure mechanisms involve switching between intra- and inter-granular crack propagation, depending on the grain size met by the crack tip. Cube-corner nanoindentation at meso-scale generates cracks and enables fracture toughness estimation, while TEM analysis of the crack tip area confirms no dislocation activity and 3D-Electron Back Scattered Diffraction technique confirms the mixed crack propagation behavior. At micro-scale, micro-pillar compression stress-strain curves and failure mechanisms are comparable with bulk samples testing analysis. These results can be used to provide design guidelinesmore » for more crack-resistant TE alloys.« less

Authors:

Aumand, Matthieu ^[1]; Amiard, Guillaume ^[2]; He, Ran ^[3]; Ren, Zhifeng ^[3]; White, Ken W. ^[3]; Thilly, Ludovic  ^[2]

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+ Show Author Affiliations

1. Univ. of Poitiers (France); Univ. of Houston, TX (United States)
2. Univ. of Poitiers (France)
3. Univ. of Houston, TX (United States)

Publication Date:

Wed Nov 07 00:00:00 EST 2018

Research Org.:

Univ. of Houston, TX (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1611557

Grant/Contract Number:  

SC0010831

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Applied Physics

Additional Journal Information:

Journal Volume: 124; Journal Issue: 17; Journal ID: ISSN 0021-8979

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Physics; Crystallographic defects; Electron microscopy; Fracture mechanics; Plasticity; Deformation; Nano-indentation; Electron diffraction; Stress strain relations; Functions and functionals; Thermoelectricity