High temperature thermoelectric properties of Bi2Sr2Co2Oy/Ag composites

Bi2Sr2Co2Oy/Ag composites have been synthesized by solid state reaction by using the Bi2Sr2Co2Oy powder and Ag2O powder as the precursors. Both X-ray diffraction and X-ray photoelectron spectroscopy measurements reveal metallic Ag mainly precipitates as the second phase in the film rather than being doped into the crystal lattice of Bi2Sr2Co2Oy. With the increase of Ag content in the composites, the resistivity is remarkably decreased while the seebeck coefficient is hardly affected due to the size of dispersed Ag particles is much smaller than that of Bi2Sr2Co2Oy matrix, resulting in an enhancement of power factor. Moreover, a small amount of Ag addition results in a slight decrease of thermal conductivity and further addition leads to an increase of thermal conductivity. Sample of Bi2Sr2Co2Oy/3 wt% Ag exhibits a figure of merit of about 0.26 at 973 K, indicating it is a promising thermoelectric candidate for high temperature applications.

► High temperature thermoelectric properties of Bi2Sr2Co2Oy/Ag composites have been investigated.
► The resistivity is remarkably decreased while the seebeck coefficient is hardly affected with increasing Ag content.
► A small addition of Ag can decrease the thermal conductivity due to the enhanced phonon scattering by the fine Ag particles.
► Sample of Bi2Sr2Co2Oy/3 wt% Ag has a ZT of about 0.26 at 973 K, which is the best value so far reported for Bi2Sr2Co2Oy.