Barium additions have been shown to lead to a decrease in both electrical conductivity and thermopower in some cases 41,61 but also to an increase in figure of merit in another study.31 The latter study showed a significant effect of processing conditions on the measured properties,soitis possible that microstructural differences may contribute to the observed effects of barium additions. Although Sr3Co4O9 has a lower conductivity than Ca3Co4O9, small strontium additions to Ca3Co4O9 do not significantly affect the electrical conductivity,but lead to adecrease in thermal conductivity and thus a small increase in the figure of merit.48