Improvement of the Thermoelectric Characteristics of Fe-doped Misfit-layered Ca3Co4−xFexO9+δ (x=0, 0.05, 0.1, and 0.2)

[[abstract]]The authors report measurements of the electrical resistivity, Seebeck coefficient, and thermal conductivity for a series of misfit-layered oxides Ca3Co4−xFexO9+δ (x = 0, 0.05, 0.1, 0.15, 0.2) prepared by solid state reaction. Structural parameters are refined with superspace group of X2/m(0b0)s0 using powder x-ray diffraction data. With partial substitution of Fe+2 for Co+3, the resistivity decreases, while the thermopower increases simultaneously. The x = 0.05 sample exhibits a higher figure of merit (Z = 3.01×10−4 K−1) than that of Ca3Co4O9+δ (0.33×10−4 K−1) at 300 K, indicating much improvement of thermoelectric characteristics via partial substitution of Fe for Co