Preparation and Thermoelectric Properties of Bi Doped Ca_3Co_4O_9 Based Thermoelectric Materials

摘要

Polycrystalline Ca_(3-x)Bi_xCo_4O_9 samples have been prepared by solid-phase reaction followed by spark plasma sintering process. The thermoelectric properties have been systematically investigated from room temperature to near 1000K. It is found that the change of the carrier concentration leads to the change of resistivity, which is mainly associated with doping induced point defect phonon scattering. The change of the thermal potential mainly comes from the spin entropy. In addition, polycrystalline Ca_(3-x)Bi_xCo_4O_9 had a maximum figure of merit of 0.30 at 973 K, which was about 50% higher than Ca_3Co_4O_9. It indicated that doping approach can effectively improve the thermoelectric performance of Ca_3Co_4O_(9+δ)-based material.