The effect of Ag addition on electrical properties of the thermoelectric compound Ca3Co4O9

Ca3Co4O9/Ag composites incorporating different amounts of Ag were synthesized by solid-state reaction. Scanning electron microscopy revealed Ag particles dispersed among and combined with Ca3Co4O9 grains several times larger in size. The electrical resistivity (ρρ) of the composites is favorably lower than that of Ca3Co4O9 alone and decreases with increasing Ag content. It can thus be inferred that the highly conductive Ag particles between the oxide grains contribute to the reduction of ρρ. Although minimal in smaller amounts, the addition of Ag also seems to have a negative impact on the Seebeck coefficient (S) of the composites due to its poor S  . Since the reduction of ρρ is more significant than the degradation of S, the power factor is found to be improved by the addition of 10 wt% Ag.

BSE images of fractured cross-sections of Co349/Ag composites containing (a) 5 wt%, (b) 10 wt%, and (c) 20 wt% of Ag. White spots in the BSE images correspond to Ag particles. (d) An SEM image of a fractured cross-section of Co349/Ag composite at 20 wt%. Almost the same microstructure was observed in other hot-forged samples.Figure optionsDownload as PowerPoint slide