Use of laser technology to produce high thermoelectric performances in Bi2Sr2Co1.8Ox

Bi2Sr2Co1.8Ox bulk polycrystalline ceramics were prepared by conventional sintering of powders, obtained by polymer solution method and by directional growth using the laser floating zone technique. Microstructural analysis showed randomly oriented grains in the classical sintered materials, while in the laser-textured samples well oriented crystals with the c-axis nearly perpendicular to the growth direction were observed. A significant reduction on electrical resistivity, compared with the sintered materials, was observed due to the decrease on the secondary phases content. As a consequence, a raise on the power factor of about 2 and 5 times, compared with the classically sintered samples, was obtained for the as-grown and annealed laser-textured samples, respectively. The maximum power factor obtained at 650 degrees C in the annealed laser-textured samples (similar to 0.20 mW/K-2 m) is much higher than the best value obtained in sinter-forged textured materials at the same temperature. (C) 2015 Elsevier Ltd. All rights reserved.