Influence of Bi substitution with rare-earth elements on the transport properties of BiCuSeO oxyselenides

Abstract

In this study, we demonstrate that introducing of rare-earth elements, $R$ = La or Pr, into the Bi-O charge reservoir layer of BiCuSeO leads to an increase of both, the charge carrier concentration and the effective mass. Although the charge carrier mobility slightly decreases upon Bi${}^{3+}$ to $R^{3+}$ substitution, the electronic transport properties are significantly improved in a broad temperature range from 100 K to 800 K. In particular, the electrical resistivity decreases by two times, while the Seebeck coefficient drops from 323 $\mu$V K${}^{-1}$ to 238 $\mu$V K${}^{-1}$ at 800 K. Thus, a power factor of nearly 3 $\mu$W cm${}^{-1}$ K${}^{-2}$ is achieved for Bi${}_{0.92}$La${}_{0.08}$CuSeO sample at 800 K. Meanwhile, a noticeable decrease of the lattice thermal conductivity is observed for the substituted samples, which can be attributed to the enhanced point defect scattering mostly originated from atomic mass fluctuations between $R$ and Bi. Ultimately, a maximum $zT$ value of nearly 0.34 at 800 K is obtained for the Bi${}_{0.92}$La${}_{0.08}$CuSeO sample, which is ~30% higher than that of pristine BiCuSeO.

15 pages, 8 figures, 3 tables; Supplemental information: 18 pages, 15 figures, 2 tables

References in corpus (1)

• Thermoelectric properties of Sm-doped BiCuSeO oxyselenides fabricated by two-step reactive sintering