| abstract |
(57) [Problem] To provide a material composed of a less toxic element, having excellent heat resistance, chemical durability and the like, and having high thermoelectric conversion efficiency. A general formula: Ca 3-x RE x Co 4 O y (wherein, R E is a rare earth element, 0 ≦ x ≦ 0.5, 8.5 ≦ y ≦ A composite oxide having a Seebeck coefficient of 100 μV / K or more and an electric conductivity of 10 3 S / m or more at a temperature of 300 ° C. or more. |