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

Abstract : 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 Ge 1−x Al x Te (x = 0-0.08) alloys processed by Spark Plasma Sintering are presented here. Being isoelectronic to Ge 1−x In x Te and Ge 1−x Ga x Te, which were reported with improved thermoelectric performances in the past, the Ge 1−x Al x Te 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 Ge 1−x Al x Te to exhibit a reduced thermoelectric figure of merit, unlike its In and Ga congeners. Additionally, divalent Ba-doping [Ge 1−x Ba x Te (x = 0-0.06)] is also studied.
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Bhuvanesh Srinivasan, Alain Gellé, Jean-François Halet, Catherine Boussard-Plédel, Bruno Bureau. Detrimental Effects of Doping Al and Ba on the Thermoelectric Performance of GeTe. Materials, MDPI, 2018, 11 (11), pp.2237. ⟨10.3390/ma11112237⟩. ⟨hal-01926269⟩

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