We have carried out O K - and Co L2,3 -edge x-ray absorption studies on misfit-layered oxides of polycrystalline Ca3 Co4-x Fex O9+δ (x=0,0.05,0.1,0.15). The analyses of integrated absorption intensity show that the number of Co 3d unoccupied states decreases upon partial substitution of Fe for Co, which correlates well the variation trend of the room-temperature resistivity with x. Nevertheless, the number of O 2p unoccupied states increases with x. Both Hall and thermopower measurements indicate that the majority carrier is of hole type for Ca3 Co4-x Fex O9+δ. Therefore, the decrease of O 2p occupancy should be responsible for the increase of the hole carrier concentration upon partial substitution of Fe for Co.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)