Growth rate effect on microstructure and thermoelectric properties of melt grown Bi ₂ Ba ₂ Co ₂ O _x textured ceramics

AbstractBi2Ba2Co2Ox thermoelectric (TE) ceramics have been grown from the melt using the laser floating zone method at different growth rates (15, 30 and 90 mm h−1). Microstructural analysis has shown an improvement of the grain alignment and a reduction of secondary phases when the growth speed is decreased. These microstructural features have been reflected in the TE performances, with a reduction of the electrical resistivity and, as a consequence, at significant increase in the power factor values, reaching ∼0·15 mW K−2 m−1 at 650°C for the samples grown at 15 mm h−1, which is much higher than the typical values obtained in these materials.