Structural and Electronic
Transport Properties in
Sr-Doped BiCuSeO
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Abstract
We report on the structural and electronic transport
properties
of BiCuSeO based compounds, that have recently been reported as promising
thermoelectric materials with figure of merit ZT > 0.8 at 923 K,
and
share the same crystal structure as the high-Tc iron based 1111 oxypnictides.
We show that the substitution of Bi<sup>3+</sup> by Sr<sup>2+</sup> induces a strong decrease of the electrical resistivity up to the
solubility limit reached for <i>x</i> = 0.35, which originates
from the strong increase of the carriers concentration. Two anomalies
in the resistivity curves have been observed, one for the undoped
compound near 260 K and the other for the doped samples at very low
temperature. However, structural and magnetic measurements do not
provide indications of structural or magnetic phase transition or
superconductivity as it had been previously suggested in BiCu<sub>1–<i>x</i></sub>OS. We show that the thermoelectric
properties of Bi<sub>1–<i>x</i></sub>Sr<sub><i>x</i></sub>CuSeO materials can be well understood through the
analysis of the electronic band structure and the density of states
close to the Fermi level and we provide possible directions toward
the enhancement of the thermoelectric figure of merit of these materials