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 Cu0.01Bi2Te2.7Se0.3, [Cu0.01Bi2Te2.7Se0.3]0.98Ni0.02, and
Bi0.88Sb0.12. 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
