The phase diagram and thermodynamics of sodium fulleride from electrochemical measurements

Phase relations and thermodynamic properties of sodium fulleride (NaxC60)have been measured up to x=6 by the electromotive force (EMF) method. Na beta -alumina was used as the solid electrolyte and Na was added to the cell containing a fixed amount of fullerene by coulometric titration. The phase diagram is characterized by alternate single-phase regions (EMF varying with composition) and two-phase regions (EMF plateaus). At 599 K, the Gibbs …