Fabrication and high temperature thermoelectric properties of c-axis oriented Na0.68CoO:Ag nanocomposite thin films

c-Axis oriented Na0.68CoO2:Ag composite thin films with metallic Ag nanoparticles embedded in the Na0.68CoO2 matrix have been fabricated by post-annealing the PLD-grown CoO:Ag precursor film in Na vapor at high temperatures. The nanosized Ag inclusions can greatly improve the electrical conductivity while retaining the Seebeck coefficient of Na0.68CoO2 films, resulting in an enhanced power factor. The power factor of the 5.0 wt.% Ag-added Na0.68CoO2 films reaches 1.85 mW/m K2 at 800 K, which is about 2 times higher than that of Ag-free films. Moreover, the thermal conductivity in these nanocomposite films is expected to be suppressed due to the enhanced phonon scatterings on nanoinclusions. The results demonstrated that adding Ag nanoinclusions is an effective way to improve the thermoelectric performance of NaxCoO2 films.