A correlative study of interfacial segregation in a Cu-doped TiNiSn thermoelectric half-Heusler alloy

Halpin, J. E., Jenkins, B., Moody, M. P., Webster, R. W.H., Bos, J.-W. G., Bagot, P. A.J. and MacLaren, D. A. (2022) A correlative study of interfacial segregation in a Cu-doped TiNiSn thermoelectric half-Heusler alloy. ACS Applied Electronic Materials, 4(9), pp. 4446-4454. (doi: 10.1021/acsaelm.2c00699) (PMID:36185076) (PMCID:PMC9520967)

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Abstract

The performance of thermoelectric materials depends on both their atomic-scale chemistry and the nature of microstructural details such as grain boundaries and inclusions. Here, the elemental distribution throughout a TiNiCu0.1Sn thermoelectric material has been examined in a correlative study deploying atom-probe tomography (APT) and electron microscopies and spectroscopies. Elemental mapping and electron diffraction reveal two distinct types of grain boundary that are either topologically rough and meandering in profile or more regular and geometric. Transmission electron microscopy studies indicate that the Cu dopant segregates at both grain boundary types, attributed to extrusion from the bulk during hot-pressing. The geometric boundaries are found to have a degree of crystallographic coherence between neighboring grains; the rough boundaries are decorated with oxide impurity precipitates. APT was used to study the three-dimensional character of rough grain boundaries and reveals that Cu is present as discrete, elongated nanoprecipitates cosegregating alongside larger substoichiometric titanium oxide precipitates. Away from the grain boundary, the alloy microstructure is relatively homogeneous, and the atom-probe results suggest a statistical and uniform distribution of Cu with no evidence for segregation within grains. The extrusion suggests a solubility limit for Cu in the bulk material, with the potential to influence carrier and phonon transport properties across grain boundaries. These results underline the importance of fully understanding localized variations in chemistry that influence the functionality of materials, particularly at grain boundaries.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Halpin, Dr John and Webster, Mr Robert and MacLaren, Dr Donald and Bagot, Dr Paul
Authors: Halpin, J. E., Jenkins, B., Moody, M. P., Webster, R. W.H., Bos, J.-W. G., Bagot, P. A.J., and MacLaren, D. A.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
College of Science and Engineering > School of Physics and Astronomy
Journal Name:ACS Applied Electronic Materials
Publisher:American Chemical Society
ISSN:2637-6113
ISSN (Online):2637-6113
Published Online:23 August 2022
Copyright Holders:Copyright © 2022 The Authors
First Published:First published in ACS Applied Electronic Materials 4(9): 4446-4454
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
172958A Focused Noble Gas Ion Beam Facility for Materials and Device Nanoanalysis - EQUIPMENT GRANTIan MacLarenEngineering and Physical Sciences Research Council (EPSRC)EP/P001483/1P&S - Physics & Astronomy
172181Nanostructured half-Heuslers for thermoelectric waste heat recoveryDonald MaclarenEngineering and Physical Sciences Research Council (EPSRC)EP/N017218/1P&S - Physics & Astronomy