Electrospinning Technique Synthesis And Electrical Transport Performance Of Ca2Co₂O-₅ With Hierarchical Structure

Thermoelectric(TE) materials is a kind of functional materails that can realize the convertion of heat and electricity. It is a very meaningful work to develop TE materials to recycle the low-grade waste heat for easing the energy crisis. Among the reported TE materials, the oxides TE materials are very suitable to be used in recycling waste heat due to their haracteristics of high temperature resistant. For this reason, the layer calcium cobalt oxides has aroused wide interests because of their high Seebeck coefficient, low thermal conductivity and high thermal stability. As an important number of the layer calcium cobalt oxides, Ca 2 Co 2 O 5 is regarded as a promising TE material in the field of recycling waste heat.Herein, we report that one dimension(1D) hierarchical structure Ca 2 Co 2 O 5 was synthesized firstly by electrospinning. By chosing the suitable raw materials and solvents,the precursor solution was prepared and spun successfully. Then the asspun nanofibers were sintered, and the product was obtained by adjusting sintering process. Scanning electron microscope(SEM), X-ray diffraction(XRD) and Transmission electron microscope(TEM) were used to characterize the samples.The hierarchical structure was assembled by nanoplates with thickness ranging from 30 nm to 50 nm. The formation mechanism of the morphology was investigate. The result of measurement of Seebeck and electron conductivity show that the samples has good thermoelectric performance. High Seebeck coefficient was realized with value of 191 μV·K-1 at 690 °C while the electron conductivity was 51 S·cm-1. The highest power factor was 1.84 W·m-1·K-2, which is 14.4% higher than the sample prepared by SolGel method..To get higher TE performance, we synthesized Ca 2 Co 2 O 5 samples with Ag-doped by electrospinning. We found that the diffraction peak in the XRD partterns of the samples prepared by doping different mass of Ag deviated to small angle, indicating that the Ca2+ were substituted by Ag+ partially. Thermoelectric properties of the samples were tested and found that Ag doping can significantly improve the conductivity of the material, the reason is that the material with the Ag doping can make carrier concentration increase, but the negative effects will make Seebeck coefficient decreases. The product of the power factor is calculated, power factor of samples with Ag incorporated will be higher than the undoped samples after 500 °C.