Experimental determination of the Lorenz number in Cu 0.01Bi 2Te 2.7Se 0.3 and Bi 0.88Sb 0.12

Abstract

Nanostructuring has been shown to be an effective approach to reduce the lattice thermal conductivity and improve the thermoelectric figure of merit. Because the experimentally measured thermal conductivity includes contributions from both carriers and phonons, separating out the phonon contribution has been difficult and is mostly based on estimating the electronic contributions using the Wiedemann-Franz law. In this paper, an experimental method to directly measure electronic contributions to the thermal conductivity is presented and applied to Cu 0.01Bi 2Te 2.7Se 0.3, [Cu 0.01Bi 2Te 2.7Se 0.3] 0.98Ni 0.02, and Bi 0.88Sb 0.12. By measuring the thermal conductivity under magnetic field, electronic contributions to thermal conductivity can be extracted, leading to knowledge of the Lorenz number in thermoelectric materials. © 2012 American Physical Society.