Thermoelectric properties of sol–gel derived cobaltite Bi2Ca2.4Co2Oy

Layered misfit cobaltite Bi2Ca2.4Co2Oy has been synthesized by a sol–gel method. This compound exhibits large thermoelectric (TE) power (S300 K∼170 μV K−1), low resistivity (ρ300 K∼42 mΩ cm) and relatively small thermal conductivity (κ300 K∼2.8 W K−1 m−1) at room temperature. Furthermore, the resistivity of this compound displays a metallic behavior above T⁎∼150 K with a semiconducting behavior below this temperature. This abnormal behavior in resistivity is analogous to those observed in Sr and Ba based misfit cobaltites. The observed features of the TE have been discussed based on the narrow band model.