Thermoelectric properties of La$_{1-y}$Sr$_{y}$Rh$_{1-x}$Co$_{x}$O$_{3}$

We have studied thermoelectric properties of the perovskite-type rhodium oxide LaRhO$_{3}$ to clarify the electronic state of La$_{1-y}$Sr$_{y}$CoO$_{3}$. We have focused on Rh oxides as a reference to Co oxide, because Rh ions are stable in the low-spin state. To reveal the difference of the thermoelectric properties between La$_{1-y}$Sr$_{y}$RhO$_{3}$ and La$_{1-y}$Sr$_{y}$CoO$_{3}$, we have measured thermoelectric properties of La$_{1-y}$Sr$_{y}$Rh$_{1-x}$Co$_{x}$O$_{3}$. XRD analysis revealed that the crystal structure of La$_{1-y}$Sr$_{y}$Rh$_{1-x}$Co$_{x}$O$_{3}$ changes from orthorhombic to rhombohedral above around x$\sim $0.75. The resistivity at 300 K decreases with the Co concentration, whereas the magnitude of the thermopower takes a maximum around x$\sim $0.25. This phenomenon clearly suggests a certain correlation between Rh and Co ions.