Enhancement of the thermoelectric properties of directionally grown Bi–Ca–Co–O through Pb for Bi substitution

Thermoelectric performances on cobaltite ceramics can be changed by doping followed by grain orientation methods. This can be performed by the Laser Floating Zone (LFZ) method on samples with different substitutions in the Rock Salt sublattice. In this work, Bi2−xPbxCa2Co1.7Oy (x = 0.0, 0.2, 0.4 and 0.6) ceramics have been directionally grown at 30 mm/h. In all the cases, samples show a microstructure composed, mainly, of alternated grains of the thermoelectrical phase and the solid solution Bi(Pb)–Ca–O, with small CoO inclusions. It has been found an important improvement on the resistivity and thermopower for samples with 0.4 Pb substitution, leading to power factor values higher than usual in misfit cobaltites obtained by conventional solid state routes.