Cation ratio of Na-Co system oxides formed in calcination process and thermoelectric properties

The products of Na-Co-system oxides were prepared using Na2CO3, Co3O4 and other ingredient powders by calcination process. Particular interest is dedicated to the composition of the powder crystals as been formed by the calcination process. It has been found that the composition of the powder crystals always results in NaxCo2Oy crystals regardless of the nominal composition, where x is a little above 1.3. For calcination powders of other concentrations, Na-oxides or Co-oxides have been found to remain as contamination, which then cause a decrease in thermoelectric performance.