Thermoelectric properties of the aliovalent half-Heusler alloy Zn0.5Ti0.5NiSb with intrinsic low thermal conductivity
Abstract
Using mixtures of aliovalent elements to achieve a valence balanced electronic state is a rapidly emerging area in half-Heusler thermoelectric materials research. Here, we report on Zn0.5Ti0.5NiSb, a combination of ZnNiSb and TiNiSb, which by adjusting the Zn/Ti-ratio can be made p- and n-type, achieving peak zT = 0.18 at 793 K and zT = 0.33 at 700 K, respectively. These promising values are underpinned by a low lattice thermal conductivity, κL = 2.7 W m−1 K−1 at 340 K, similar for all samples, decreasing to 1.25 W m−1 K−1 at 793 K. Transport data reveal similar weighted electronic mobilities for p- and n-type samples, suggesting similar zT should be possible. For both polarities, a transition to degenerate conduction is observed, superposed on intrinsic semiconducting behaviour with a bandgap Eg = 0.4 eV. Neutron and synchrotron X-ray diffraction experiments, including total scattering, indicate the absence of interstitial metals and do not reveal strong local structural variations. The absence of substantial mass disorder and lattice strain points towards bond disorder as a possible origin for the low κL. This work describes a new materials system and provides further insight into the impact of aliovalent alloying in the half-Heusler structure.
Citation
Kennedy , B , Kimber , S , Checchia , S , Shawon , A K M A , Zevalkink , A , Suard , E , Buckman , J & Bos , J-W G 2023 , ' Thermoelectric properties of the aliovalent half-Heusler alloy Zn 0.5 Ti 0.5 NiSb with intrinsic low thermal conductivity ' , Journal of Materials Chemistry A , vol. 11 , no. 43 , pp. 23566-23575 . https://doi.org/10.1039/D3TA04514E
Publication
Journal of Materials Chemistry A
Status
Peer reviewed
ISSN
2050-7488Type
Journal article
Description
The EPSRC is acknowledged for funding the research into new half-Heusler materials, through award (EP/N01717X/1) and for a PhD studentship for B. F. K.Collections
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