Thermoelectric Properties of Ca3Co4O9 Using Microwave Synthesis and Sintering

Ca 3 Co 4 O 9 powders and ceramics were synthesized and sintered using microwave-assisted heating method.Another batch of powders was calcined by the conventional heating method and this powder was used to produce ceramics sintered by microwave sintering aiming to compare with those prepared by microwave method. The formation of the phases based on calcination method and time was assessed by X-ray diffractometry. The synthesis and sintering methods affected various properties of the ceramics, including grain size, density, phase amount, Seebeck coefficient, thermal conductivity and electrical conductivity. Microwave heating method reduced the time required for the powder synthesis and sintering of ceramics. Ceramics produced using powder obtained by the conventional method presented Figure of Merit (ZT) values of approximately 0.04. However, these values were reduced for the ceramics produced by microwave heating reaching a value of about 0.02. The evaluation of the thermoelectric properties of the Ca 3 Co 4 O 9 ceramics suggests that the main issue to enhance the Figure of Merit of the CCO ceramics is related to density and Ca 3 Co 4 O 9 phase amount present in the ceramics.