Effect of Sr substitution for Ca on the Ca3Co4O9 thermoelectric properties

Ca3−xSrxCo4O9 polycrystalline thermoelectric ceramics with small amounts of Sr have been synthesized by the classical solid state method. Microstructural characterizations have shown that all the Sr has been incorporated into the Ca3Co4O9 and Ca3Co2O6 structures and no Sr-based secondary phases have been produced. Apparent density measurements have shown that samples slightly increase their density until 0.05 Sr content, decreasing for higher contents. Electrical resistivity decreases and Seebeck coefficient slightly raises when Sr content increases until 0.07 Sr addition. The improvement in both parameters leads to higher power factor values than the usually obtained in samples prepared by the conventional solid state routes and close to those obtained in textured materials.