Influence of Mn-site doped with Ru on the high-temperature thermoelectric performance of CaMnO3−δ

Thermoelectric properties were measured from room temperature to 1000 K to study the effects of doping of Ru for Mn-site on the thermoelectric performance of CaMnO3−δ. The electrical resistivity shows a sharp decrease upon Ru doping. The Seebeck coefficients of all the samples are negative, and their absolute values remain fairly large even after Ru doping. Among the samples of CaMn1−xRuxO3−δ (x=0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.15, 0.18), CaMn0.96Ru0.04O3−δ has the largest power factor, 1.85×10−4 W/mK2 at 1000 K. An increase or a decrease of x value results in a marked decrease of the power factor. The thermal conductivity and the figure of merit Z of CaMn0.96Ru0.04O3−δ is 2.88 W/mK and 0.64×10−4 K−1 at 1000 K, respectively.