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Detrimental Effects of Doping Al and Ba on the Thermoelectric Performance of GeTe

Univ. Rennes, ISCR UMR 6226, IPR UMR 6251, CNRS, 35000 Rennes, France
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Author to whom correspondence should be addressed.
Materials 2018, 11(11), 2237; https://doi.org/10.3390/ma11112237
Received: 15 October 2018 / Revised: 6 November 2018 / Accepted: 9 November 2018 / Published: 11 November 2018
(This article belongs to the Special Issue Advanced Glasses, Composites and Ceramics for High Growth Industries)
GeTe-based materials are emerging as viable alternatives to toxic PbTe-based thermoelectric materials. In order to evaluate the suitability of Al as dopant in thermoelectric GeTe, a systematic study of thermoelectric properties of Ge1−xAlxTe (x = 0–0.08) alloys processed by Spark Plasma Sintering are presented here. Being isoelectronic to Ge1−xInxTe and Ge1−xGaxTe, which were reported with improved thermoelectric performances in the past, the Ge1−xAlxTe system is particularly focused (studied both experimentally and theoretically). Our results indicate that doping of Al to GeTe causes multiple effects: (i) increase in p-type charge carrier concentration; (ii) decrease in carrier mobility; (iii) reduction in thermopower and power factor; and (iv) suppression of thermal conductivity only at room temperature and not much significant change at higher temperature. First principles calculations reveal that Al-doping increases the energy separation between the two valence bands (loss of band convergence) in GeTe. These factors contribute for Ge1−xAlxTe to exhibit a reduced thermoelectric figure of merit, unlike its In and Ga congeners. Additionally, divalent Ba-doping [Ge1−xBaxTe (x = 0–0.06)] is also studied. View Full-Text
Keywords: Thermoelectrics; GeTe; Al-doping; Ba-doping; loss of band convergence; lowered zT Thermoelectrics; GeTe; Al-doping; Ba-doping; loss of band convergence; lowered zT
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MDPI and ACS Style

Srinivasan, B.; Gellé, A.; Halet, J.-F.; Boussard-Pledel, C.; Bureau, B. Detrimental Effects of Doping Al and Ba on the Thermoelectric Performance of GeTe. Materials 2018, 11, 2237.

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