Doping effects of Ba, La and Sr for the A-site in double-perovskite type oxide A2B'MoO6(A= Sr, Ca, B'= Fe, Mn) are investigated on the thermoelectric properties of the oxides. The Seebeck coefficient, S, shows that all the samples of the Sr2MnMoO6 and Ca2FeMoO6 systems under investigation are n-type over the whole temperature range measured. In both La- and Ba-doped Sr2MnMoO6 systems, the dimensionless figure-of-merit, ZT, of the samples increased with increasing temperature. The thermal conductivity, {kappa}, 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. As a consequence, the ZT values of 0.08 was obtained for Sr1.7Ba0.3FeMoO6 at 1000 K. In the Ca2FeMoO6 system, S2{sigma} of Ca1.8Sr0.2FeMoO6 reached ca. 3.5*10-4 W/mK2, being the largest of all samples in this study. However, the highest ZT value of the sample was 0.06 at 1200 K.
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