Thermoelectric Properties of $R_{1-x}$Sr$_{x}$CoO$_{3}$ Perovskites*

Cobalt oxide materials have recently shown promise for use in thermoelectric applications due to enhancement of the Seebeck coefficient ($S)$ by the spin and orbital degeneracy of the Co$^{3+}$ and Co$^{4+}$ ions. We have studied Sr substituted $R$CoO$_{3}$ ($R$ = rare earth elements) perovskites that exhibit increased transition temperatures to the low-spin ground state, which is required for achieving enhanced $S$. We have found that Gd is the smallest $R$ for which the homogenous Sr substitution is possible. We will present structural and thermoelectric properties of these materials with 0 $< \quad x \quad <$ 0.5. We will describe our search for materials with optimal degeneracy ratios, which are stable within practical operating temperature ranges for thermoelectric applications.