Effects of mechanical milling and Ag addition on thermoelectric properties of NaxCo2O4

The effects of mechanical milling and Ag dispersion on the thermoelectric performance of NaxCo2O4 were investigated. The Seebeck coefficient was enhanced by both mechanical milling and Ag addition. Ag addition was effective in reducing the electrical resistivity, resulting in the significantly large power factor. However, the dimensionless figure of merit could not be improved by mechanical milling and Ag addition, because Ag particles around 10 μm in size in the NaxCo2O4 matrix phase significantly increased the thermal conductivity.