High-temperature thermoelectric properties of the double-perovskite ruthenium oxide (Sr$_{1-x}$La$_x$)$_2$ErRuO$_6$

TL;DR

This study investigates the thermoelectric properties of doped double-perovskite ruthenates, revealing promising Seebeck coefficients and low thermal conductivity at high temperatures, with insights into their electronic states and conduction mechanisms.

Contribution

It provides new experimental data on the thermoelectric performance of La-doped Sr2ErRuO6 and Sr2YRuO6, highlighting their potential for oxide thermoelectric applications.

Findings

Large Seebeck coefficient of -160 μV/K at 800 K

Low thermal conductivity of 7 mW/cmK at 800 K

Doped electrons in Ru4+ low spin state

Abstract

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.