The maximum ZT value of 0.39 at 600 1C was reached for the
sample with x¼0.02 Bi doped with the addition of SWCNHs. These
carbon nanostructures increased considerably the electrical conductivity
and slightly the thermal conductivity. The particular role of
these carbon nanostructures will be the subject of further investigations
in order to deep understand their effect on thermoelectric
properties.