Thermoelectric properties of barium doped calcium cobaltite obtained by simplified chemical route

Abstract

Calcium cobaltite (CCO) thermoelectric ceramics in Ca 3 Co 4 O 9 and Ca 2.95 Ba 0.05 Co 4 O 9 compositions were produced by a simplified chemical route developed in this study. Undoped ceramics sintered at 1193 K for 12 h presented a bulk density equivalent to 77% of the theoretical density, one of the highest values ever found for conventionally sintered undoped calcium cobaltite. The presence of barium improved densification, reaching 80% of the theoretical density. Thermoelectric properties were discussed based on X-ray diffraction patterns, scanning electron micrographs, Seebeck coefficient, electrical and thermal conductivity. Electrical characterizations presented values of about 6200 and 7000 S/m at 873 K for undoped and doped ceramics, respectively. However, all ceramics presented almost the same range of activation energy values, indicating the possibility of non-effective substitution through this methodology. The maximum global PF (power factor) was 0.10 mW.m-1 .K-2 for the densest undoped sample and an overall ZT (dimensionless figure of merit) of 0.07 for the undoped ceramic at 873 K.

Fabrication and Performance Analysis of AZO and MCCO as Thin Film-Thermoelectric Generator Materials

“…ZnO is an n-type material with good chemical and thermal stability at high temperatures, so it is suitable to be applied as a high-temperature thermoelectric [13 -16]. Like ZnO, CaCO3 is a p-type material with a high Seebeck coefficient and high electrical conductivity, making it suitable for a thermoelectric material [17]. Unfortunately, the resistivity of ZnO and CaCO3 is still high enough to be used as a thermoelectric so doping of the material is needed [14 -16].…”