Alloying and doping control in the layered metal phosphide thermoelectric CaCuP
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We recently identified CaCuP as a potential low cost, low density thermoelectric material, achieving zT = 0.5 at 792 K. Its performance is limited by a large lattice thermal conductivity, κL, and by intrinsically large p-type doping levels. In this paper, we address the thermal and electronic tunability of CaCuP. Isovalent alloying with As is possible over the full solid solution range in the CaCuP1–xAsx series. This leads to a reduction in κL due to mass fluctuations but also to a detrimental increase in p-type doping due to increasing Cu vacancies, which prevents zT improvement. Phase boundary mapping, exploiting small deviations from 1:1:1 stoichiometry, was used to explore doping tunability, finding increasing p-type doping to be much easier than decreasing the doping level. Calculation of the Lorenz number within the single parabolic band approximation leads to an unrealistic low κL for highly doped samples consistent with the multiband behavior in these materials. Overall, CaCuP and slightly Cu-enriched CaCu1.02P yield the best performance, with zT approaching 0.6 at 873 K.
Quinn , R , Biswas , R & Bos , J-W G 2023 , ' Alloying and doping control in the layered metal phosphide thermoelectric CaCuP ' , ACS Applied Electronic Materials . https://doi.org/10.1021/acsaelm.3c00828
ACS Applied Electronic Materials
Copyright © 2022 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY 4.0.
DescriptionEngineering and Physical Sciences Research Council - EP/R023751/1, EP/T019298/1, EP/W037300/1; Leverhulme Trust - RPG-2020-177
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