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(Bi,Sb)2Te3-PbTe chalcogenide alloys: Impact of the cooling rate and sintering parameters on the microstructures and thermoelectric performances

: Jacquot, A.; Thomas, J.; Schumann, J.; Jägle, M.; Böttner, H.; Gemming, T.; Schmidt, J.; Ebling, D.


Journal of Materials Research 26 (2011), No.15, pp.1773-1784
ISSN: 0884-2914
ISSN: 2044-5326
Journal Article
Fraunhofer IPM ()
Fraunhofer IFAMDD ()
n-type; Bi2Te3; semiconductor; figure of merit

(Bi,Sb)(2)Te(3) + 4 mol% PbTe was quenched in water and on a rotating copper wheel (melt spinning). It was found that PbTe was immiscible in (Bi,Sb)(2)Te(3) when the material is quenched in water and that the thermoelectric figure of merit increases by annealing. Natural nanostructures (nns) were found in melt-spun (Bi,Sb)(2)Te(3), whereas they were hard to detect in (Bi,Sb)(2)Te(3) alloyed with PbTe. There is a correlation between the orientation of the strain field and the nns. Within the grains of melt-spun (Bi,Sb)(2)Te(3) alloyed with PbTe, the chemical composition was homogeneous. An enrichment of Pb was found at the grain boundaries. Quenched (Bi,Sb)(2)Te(3) alloyed with 0.3 wt% PbTe have been spark plasma sintered (SPS). After optimization, the Seebeck coefficients of the melt-spun SPS (MS-SPS) materials were larger than for materials quenched in water and sintered (QW-SPS) materials. In addition, the mobility increases with the carrier concentration in MS-SPS materials, whereas it decreases in QW-SPS materials.