ScholarWorks@숙명여자대학교

초록

The electronic structures and the thermoelectric (TE) properties of the ternary chalcogenide PbBi4Te7 are investigated by using first-principles calculations within the density functional theory and the solutions of semi-classical Boltzmann equation. Employing the screened-exchange local density approximation, we found that PbBi4Te7 to be a narrow-gap semiconductor with an indirect band gap of 0.11 eV. The combination of light and heavy valence bands near the band edge gives rise to large Seebeck coefficients, S, for p-type doping, which is found to be improved by 11% from that of Bi2Te3 at room temperature (RT). Moreover, in contrast to conventional Bi2Te3 where the value of S decreases rapidly with temperatures higher than RT, the values of S increases with temperature reaching up to 350 mu VK-1 at 500 K indicating that PbBi4Te7 is a promising TE material with operating temperatures above RT. Our result also reveals that the intrinsic layered structure results in a prominent anisotropy in the TE coefficients, implying that the TE performance can be optimized by using the transport direction, as well as the type and the level of doping.

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