INTERCALATION IN SODIUM GRAPHITE ASSOCIAT ED WITH PEROXIDE IONS

We have synthesized a second stage blue graphite intercalation compoun d, by heating at 470 degrees C for 1 or 2 days, in a nickel or stainle ss steel reactor, a pyrographite sample or a single crystal immersed i n liquid pure sodium previously exposed to the atmosphere or mixed wit h a very small amount of sodium peroxide. This compound, which is very poorly reactive, is a ternary graphite-sodium-oxygen phase, with a re peat distance of 1080 pm and the chemical formula NaO0,44C5,84. We hav e shown that its intercalated sheets are five-layered, according to th e [Na-O-Na-O-Na] stacking. It appears that intercalated oxygen is in t he form of O-2(2-) anions, so that the intercalated sheets seem to be slices of sodium peroxide, which have been cut perpendicular to its c- axis. Electrical conductivity and NMR measurements have been carried o ut: they show that this compound is strongly anisotropic and exhibits a metallic character. (C) 1997 Academic Press.