Na-Site Doping of NaCo<sub>2</sub>O<sub>4</sub> Thermoelectric Materials

The K, Ca, Sr and Ce doped and non-doped γ-NaxCo2O4 samples were prepared by the solid-state reaction method. Results show that the Na-site doping might lead to an increase in the Seebeck coefficient and a decrease in the electrical conductivity of the samples. The maximum power factors of the K, Ca and Sr doped samples are respectively 2.04, 1.93 and 1.9 W·m-1·K-2, corresponding to an increase by 58%, 50% and 47% compared with that of the non-doped samples. Thus, the Na-site doping can improve the thermoelectric properties of γ-NaxCo2O4 oxides.