Optimization of Synthesis Conditions of Na0.75CoO2 for High Thermoelectric Performance

초록

Reproducibility of phase formation has been an important issue in tailoring electronic and thermal transport properties of Na (x) CoO2-based thermoelectric materials; however, optimized synthesis conditions for single phase of polycrystalline Na (x) CoO2 remain unsatisfactory. Here, we show that phase formation of a Na-Co-O-based system can be controlled by adjusting the reaction temperature. Single phase of Na0.75CoO2 was fabricated by optimized heat treatment for both suppression of Na2O vaporization and CoO phase formation. The largest thermoelectric power factor of the present compound (similar to 5.4 x 10(-4) W/mK(2) at 973 K) is comparable to that of reported values for single phase polycrystalline Na (x) CoO2 bulks. In addition, Na0.75CoO2 phase obtained by this approach was confirmed to be stable at high temperatures up to 1000 K.

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