We have synthesized an original layered rhodium oxide in the Bi-Sr-Rh-O system with alternately stacked conductive $\mathrm{Rh}{\mathrm{O}}_x$ layer and insulating $\left({\mathrm{Bi}}_{0.75}{\mathrm{Sr}}_{0.25}\right){\mathrm{O}}_{1.5}$ fluorite-type layers. Thermopower, resistivity, Hall coefficient, magnetoresistance, and magnetization measurements evidence high thermoelectric properties with Pauli-like paramagnetism and large carrier concentration $(\sim {10}^{22}{\mathrm{cm}}^{-3})$. The room-temperature resistivity, thermopower, and power factor are $1.6\mathrm{m}\Omega \mathrm{cm}$, $63\mu \mathrm{V}∕\mathrm{K}$, and $2.48\mu \mathrm{W}∕\mathrm{cm}{\mathrm{K}}^2$, respectively, which are comparable with those of the best existing $p$-type thermoelectric oxides, the misfit-layered cobalt oxides with the hexagonal $\mathrm{Cd}{\mathrm{I}}_2$-type $\mathrm{Co}{\mathrm{O}}_2$ layer. In these crystals, the temperature dependence of the resistivity and the magnetic susceptibility suggest the presence of strong electron-electron interaction. This two-dimensional material emphasizes the potential of the transition-metal oxides for thermoelectric applications.

• Received 25 April 2007

DOI:https://doi.org/10.1103/PhysRevB.76.245102