Thermoelectric properties of double-perovskite oxide Sr_<2-x>M_xFeMoO_6 (M=Ba, La)

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Doping effects for the A-site in double-perovskite type oxide Sr_<2-x>M_xFeMoO_6 (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 Sr_2FeMoO_6 systems are n-type over the measured temperature range. In particular, the power factor, S^2σ, of the Sr_2FeMoO_6 system largely increased with increasing Ba doping level up to x=0.3. As a consequence, S^2σ of Sr_<1.7>Ba_<0.3>FeMoO_6 reached ca. 0.8×10^<-4>W/mK^2, 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. 1W/mK at room temperature to ca. 0.7W/mK at 1100K. The dimensionless figure of merit, ZT, of the Badoped samples increased with increasing Ba doping level. Moreover, the ZT value drastically increased above 700K due to the S^2σ value increasing above 700K and the κ value decreasing monotonically. As a result, the ZT value of Sr_<1.7>Ba_<0.3>FeMoO_6 reached 0.31 at 1100K.
2008-12-01