Thermoelectric properties of Ca₃Co_4-xMn _xO_9+δ with x = 0.00, 0.05, 0.10, and 0.15

Ca₃Co_4-xMn_xO_9+δ (x = 0.00, 0.05, 0.10, and 0.15) sample were prepared by conventional solid state synthesis. The thermoelectric properties were measured at 15 K-300 K. The XRD results revealed that all the samples are single phase. The thermopower of all the samples was positive, indicating that the predominant carriers were holes over the entire temperature range. Both the electric resistivity and the thermopower increased with increasing Mn content. Ca₃Co _3.95Mn_0.05O_9+δ had the highest power factor of 3.40 μW cm^-1 K^-2 at 163 K, representing an improvement of about 187 % compared to undoped Ca₃Co ₄O_9+δ. These results suggested that there is scope for improving the thermoelectric characteristics via partial substitution of Mn for Co.