Valence-band structure of highly efficient p -type thermoelectric PbTe-PbS alloys

Experimental evidence is given relevant to the temperature dependence of the valence band structure of PbTe and PbTe sub(1-x) S sub(x) alloys (0.04 < or = x < or = 0.19, and its effect on the thermoelectric figure of merit ZT. The x = 0.08 sample has ZT ~ 1.55 at 773 K. The magnetic field depe...

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Bibliographic Details
Published in:Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2013-01, Vol.87 (4), Article 045203
Main Authors: Jaworski, Christopher M., Nielsen, Michele D., Wang, Hsin, Girard, Steven N., Cai, Wei, Porter, Wally D., Kanatzidis, Mercouri G., Heremans, Joseph P.
Format: Article
Language:English
Subjects:
Alloys
Bands
Condensed matter
Intermetallics
Lead base alloys
Lead tellurides
Magnetic fields
PbTe
thermoelectric
Thermoelectricity
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Summary:Experimental evidence is given relevant to the temperature dependence of the valence band structure of PbTe and PbTe sub(1-x) S sub(x) alloys (0.04 < or = x < or = 0.19, and its effect on the thermoelectric figure of merit ZT. The x = 0.08 sample has ZT ~ 1.55 at 773 K. The magnetic field dependence of the high-temperature Hall resistivity of heavily p-type (> 10 super(19) cm super(-3)) Na-doped PbTe sub(1-x) S sub(x) reveals the presence of high-mobility electrons. This casts doubts on prior analyses of the Hall coefficient suggesting that temperature induces a rapid rise in energy of the "heavy" hole relative to the "light" hole bands. The electron-like behavior is likely induced by the topology of the Fermi surface when the L- and capital sigma -bands merge. Negative values for the low-temperature thermopower are also observed. The data show that PbTe continues to be a direct-gap semiconductor at temperatures where the ZT and S super(2)[sigma] of p-type PbTe are optimal, e.g., 700-800 K.
ISSN:1098-0121
1550-235X
DOI:10.1103/PhysRevB.87.045203