We have successfully prepared thermoelectric materials NaCo2O4-delta at lower temperature (700degreesC) using aqueous sol-gel methods. We find that the electrical resistivity and thermopower of NaCo2O4-delta depend strongly on the sintering temperature and partial pressure of oxygen. The oxygen content of NaCo2O4-delta is found to decrease with increasing sintering temperature. The sample prepared at the combination of 700degreesC and pure flowing oxygen exhibits the highest value of power factor. (C) 2004 Kluwer Academic Publishers.