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Two solution synthetic methods, sol-gel and a polymeric route, have been studied in order to obtain Ca 3 Co 4 O 9 misfit compounds with improved thermoelectric properties, compared to the classical solid state reaction. A comparison among the final products obtained by these different methods has been performed using DTA, TGA, FTIR X-ray diffraction, scanning electron microscopy, and thermoelectric characterizations. All the samples obtained by solution synthesis show a very significative reduction on the secondary phases content. As a consequence, an important decrease on the electrical resistivity values is produced, compared to the solid state prepared samples, leading to a relatively important power factor raise.

Bi 2 Ba 2 Co 2 O x thermoelectric ceramics were textured from the melt using the laser floating zone method, at 5mm/h growth rate. Microstructure has shown a good grain alignment with the growth axis. These microstructural features have been reflected on the thermoelectric performances, with a very important increase on the power factor values, reaching ~0.4mW/K 2 .m at 650ºC, much higher than the typical values obtained in this materials so far.