Anomalous thermoelectric power of the alkali metal doped and the pyrolyzed fullerene

Abstract

We report the temperature dependent thermoelectric power (TEP) and conductivity of the alkali-metal doped bulk fullerene, Na x C 60, K x C 60 and the pyrolyzed fullerene. For K x C 60, their TEP data can be classified into two kinds according to their signs and temperature dependences. In the case of the samples with negative TEP, their TEP data show quasi-linear temperature dependence with S RT ≅ −110 μV/K. However, for the samples with positive TEP, the TEP data show big anomalies. The TEP value of the pyrolyzed C 60 is about S RT ≅ +3.8 μV/K and upon cooling, the TEP decreases quasi linearly with the change of slope at T = 180K. Our preliminary analysis indicates that the positive TEP data of doped C 60 are originated from the collectively bridged C 60 molecules while the negative TEP data are due to the electrons donated from the alkali metals in doped C 60 fullerene.