Giant improvement of thermoelectric power factor of Bi2Te3 under pressure

The pressure (P) dependencies of both the thermopower (Seebeck effect) S and the electrical resistance (R) for p-type single crystals of Bi2Te3 and indium-doped bismuth telluride (InxBi2-xTe3, 0.04 <= x <= 0.10) are reported on a pressure range of 0-8.5 GPa. The thermoelectric power factor (efficiency) (alpha = S-2/R) exhibits two maxima: the first one near similar to 1 GPa and the second near similar to 2.5-4.5 GPa. These features evidence a giant increase in the power factor by a factor of similar to 10. Possible values of the dimensionless figure of merit under pressure are also estimated. The maxima are explained in terms of pressure-driven changes in an electron structure. The second feature may be also addressed to an intermediate high-pressure phase detected in x-ray diffraction studies. (C) 2008 American Institute of Physics.