Enhanced Thermoelectric Properties of Ca3−xAgxCo4O9 by the Sol–Gel Method with Spontaneous Combustion and Cold Isostatic Pressing

Abstract

In this study, Ca3−xAgxCo4O9 ceramics were synthesized by the sol–gel method combined with spontaneous combustion and cold isostatic pressing. The Ca3−xAgxCo4O9 ceramics were characterized via X-ray diffraction and scanning electron microscopy. Thermoelectric properties of the ceramics were measured from 323 to 673 K. The results indicated that Ag doping significantly affected the microstructure and thermoelectric properties. With the increase in Ag content and gradual increase in electrical conductivity, the Seebeck coefficient first increased and then decreased, whereas the thermal conductivity exhibited the opposite case. The figure of merit, ZT, was 0.17 at 673 K for the Ca2.8Ag0.2Co4O9 sample. These results indicated that the thermoelectric properties could be optimized remarkably with the substitution of Ag.