Carbon nitride powders with high nitrogen content have been synthesized via a new, high-pressure (7.7 GPa) and relatively low-temperature (400-500 degreesC) procedure that involves a chemical reaction of hexachlorobenzene (C6Cl6) and sodium azide (NaN3) in an enclosed system for 50-70 h in the presence of a sodium flux. The obtained powder product was characterized by X-ray powder diffraction, infrared and electron energy loss spectroscopy. The nitrogen-carbon atomic ratio of the material was 1.24 +/- 0.15, which is consistent with C3N4 stoichiometry and represents the most nitrogen-rich carbon nitride yet prepared under high-pressure. Scanning electron microscopy and high-resolution transmission electron microscopy studies revealed that the material obtained was predominantly amorphous with some fraction of nanocrystallites with the reticular distance between the lattice planes approximately 0.326 nn. (C) 2003 Elsevier Science B.V. All rights reserved.