High-temperature thermoelectric properties of the double-perovskite   ruthenium oxide (Sr$_{1-x}$La$_x$)$_2$ErRuO$_6$
  We have prepared polycrystalline samples of (Sr$_{1-x}$La$_x$)$_2$ErRuO$_6$ and (Sr$_{1-x}$La$_x$)$_2$YRuO$_6$, and have measured the resistivity, Seebeck coefficient, thermal conductivity, susceptibility and x-ray absorption in order to evaluate the electronic states and thermoelectric properties of the doped double-perovskite ruthenates. We have observed a large Seebeck coefficient of -160 $\mu$V/K and a low thermal conductivity of 7 mW/cmK for $x$=0.1 at 800 K in air. These two values are suitable for efficient oxide thermoelectrics, although the resistivity is still as high as 1 $\Omega$cm. From the susceptibility and x-ray absorption measurements, we find that the doped electrons exist as Ru$^{4+}$ in the low spin state. On the basis of the measured results, the electronic states and the conduction mechanism are discussed. 
Ryohei Takahashi, Ryuji Okazaki, Yukio Yasui, Ichiro Terasaki, Takaaki   Sudayama, Hironori Nakao, Yuichi Yamasaki, Jun Okam...
cond-mat.mtrl-sci