1. Mobility Ratio as a Probe for Guiding Discovery of Thermoelectric Materials: The Case of Half-Heusler Phase ScNiSb1−xTex
- Author
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Karol Synoradzki, Kamil Ciesielski, Izabela Wolańska, Damian Szymański, and Dariusz Kaczorowski
- Subjects
Materials science ,Condensed matter physics ,Phonon ,Scattering ,Doping ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Thermoelectric materials ,01 natural sciences ,Effective mass (spring–mass system) ,chemistry ,0103 physical sciences ,Content (measure theory) ,Charge carrier ,010306 general physics ,0210 nano-technology ,Tellurium - Abstract
Analysis of bipolar thermal conductivity might be very useful in preliminary stages of thermoelectric materials discovery. Using its product---mobility ratio between electrons and holes---it is possible to choose the most promising compound from the series and pave the correct direction of doping. Current work presents positive verification of this approach for $\mathrm{Sc}\mathrm{Ni}\mathrm{Sb}$, which is anticipated to show superior mobility when tuned towards n-type behavior. In agreement with expectation, the mobility increases by an order of magnitude due to rising tellurium content in the ${\mathrm{Sc}\mathrm{Ni}\mathrm{Sb}}_{1\ensuremath{-}x}{\mathrm{Te}}_{x}$ series. The effect is most likely driven by change of the dominant charge carriers' scattering mechanism from ionized impurity influence to point defect and acoustic phonon interaction. Simultaneously, due to a highly anisotropic conduction band, the effective mass of the carriers rises towards the n-type regime. These two effects lead to an improved thermoelectric power factor of electron-doped samples, up to $40\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}{\mathrm{WK}}^{\ensuremath{-}2}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ at 740 K for ${\mathrm{Sc}\mathrm{Ni}\mathrm{Sb}}_{0.85}{\mathrm{Te}}_{0.15}$. Based on this result, we suggest n-type doping for other rare-earth-based half-Heusler compounds. Representatives of this group exhibit the smallest lattice thermal conductivity in the pristine form among any half-Heusler thermoelectrics, and are anticipated to show comparably good electrical properties to ScNiSb due to their high mobility ratio in favor of electrons.
- Published
- 2021