Improvement of thermoelectric properties in Ca3Co4O9 ceramics by Ba doping

Abstract

Ca3−xBaxCo4O9 bulk polycrystalline thermoelectric ceramics with x = 0.00, 0.01, 0.03 and 0.05 have been prepared through a classical solid state method. Microstructural characterizations of sintered samples have shown that Ba has been incorporated into the Ca3Co4O9 and/or Ca3Co2O6 structures and that no Ba-based secondary phases have been produced. The apparent density values increase when the amount of barium is raised with respect to the undoped samples, reaching a maximum value of around 77 % of the Ca3Co4O9 theoretical density, for samples with the highest amount of barium. Electrical resistivity of doped samples decreases in the whole measured temperature range with respect to the undoped ones, while Seebeck coefficient remains practically unchanged. In conclusion, the improvement in resistivity leads to power factor values which are higher than the ones measured in undoped samples, fact which makes this bulk polycrystalline compound a promising candidate for high-temperature power generation applications in oxidative environments.