Microstructure and electrical transport properties of Ca3Co4−xMnxO9+δ ceramics fabricated under two-step external magnetic field

A series of Ca3Co4−xMnxO9+δ (x=0, 0.25 and 0.5) samples were prepared under two-step external magnetic field during both processes of sol-gel and pre-pressing. The effects of Mn doping and external magnetic field on the microstructure and electrical transport properties of the samples have been studied systematically. The investigated results show that Mn-doping can improve the electrical transport properties slightly. After using external magnetic field, the textured structures of all the samples are enhanced dramatically, which results in the obvious decrease of the electrical resistivity and increase of Seebeck coefficient. The difference of ρ between the x=0.5 samples without and with external magnetic field is about 24.73 mΩ cm at room temperature. All the samples with magnetic field show higher power factors (PF), for example, the PF at x=0.5 with magnetic field can reach the maximum value of 0.29 mW/m K2 at 1073 K.