Thermoelectric properties of double-perovskite oxide Sr_2-<i>x</i><i>M</i>_<i>x</i>FeMoO₆ (<i>M</i> = Ba, La)

Abstract

Doping effects for the A-site in double-perovskite type oxide Sr2-xMxFeMoO6 (M = Ba, La) are investigated on the thermoelectric properties of the oxides. The Seebeck coefficient, S, shows that all the samples of both Ba- and La-doped Sr2FeMoO6 systems are n-type over the measured temperature range. In particular, the power factor, S2σ, of the Sr2FeMoO6 system largely increased with increasing Ba doping level up to x = 0.3. As a consequence, S2σ of Sr1.7Ba0.3FeMoO6 reached ca. 0.8 × 10-4 W/mK2, the largest value of all the samples in this study. The thermal conductivity, κ, shows a general trend in which the value decreases from ca. 1 W/mK at room temperature to ca. 0.7 W/mK at 1100 K. The dimensionless figure of merit, ZT, of the Ba-doped samples increased with increasing Ba doping level. Moreover, the ZT value drastically increased above 700 K due to the S2σ value increasing above 700 K and the κ value decreasing monotonically. As a result, the ZT value of Sr1.7Ba0.3FeMoO6 reached 0.31 at 1100 K.