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Dilute Cu2Te-alloying enables extraordinary performance of r-GeTe thermoelectrics

Thermoelectric GeTe intrinsically comes with a p-type conduction and a carrier concentration (∼1021 cm−3) significantly higher than needed (∼1020 cm−3) because of the existence of high-concentration cation vacancies (∼3%). Its rhombohedral phase (r-GeTe) has recently been found to be very interestin...

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Bibliographic Details
Published in:Materials today physics 2019-06, Vol.9, p.100096, Article 100096
Main Authors: Bu, Z., Li, W., Li, J., Zhang, X., Mao, J., Chen, Y., Pei, Y.
Format: Article
Language:English
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Summary:Thermoelectric GeTe intrinsically comes with a p-type conduction and a carrier concentration (∼1021 cm−3) significantly higher than needed (∼1020 cm−3) because of the existence of high-concentration cation vacancies (∼3%). Its rhombohedral phase (r-GeTe) has recently been found to be very interesting because of the overall high valence band degeneracy enabled by the rhombohedral distortion from its cubic structure. Existing efforts on advancing GeTe thermoelectrics usually involve a very high concentration of impurities, which usually leads to a significant simultaneous change in the band structure and scattering of both electrons and phonons. In this study, we focus on r-GeTe and illustrate Cu2Te as a particularly effective dopant, enabling carrier concentration to be optimized at a very low overall impurity concentration for minimizing the changes in the band structure and scattering. This work reveals an inherently high mobility (∼140 cm2/V-s) that has never been realized in the literature (≤90 cm2/V-s) and demonstrates the degree of rhombohedral distortion as a core descriptor for the valence band structure. A further PbTe-alloying for a reduction in lattice thermal conductivity successfully realizes an extraordinary thermoelectric performance, demonstrating the superior thermoelectric potential inherent to r-GeTe. [Display omitted] •This work reveals that Cu2Te-alloying can significantly reduce the hole concentration of GeTe.•This enables a realization of a high carrier mobility inherent to r-GeTe, because of the nearly unchanged band structure.•With PbTe-alloying for reducing lattice thermal conductivity, an extraordinary thermoelectric performance is achieved.
ISSN:2542-5293
2542-5293
DOI:10.1016/j.mtphys.2019.100096