Crystalline carbon nitrides have been synthesized by using a novel solvothermal method in which the reaction temperature and pressure were varied to determine the possible range for the formation of the crystalline phases. The chemical composition and states of elements were analyzed using X-ray photoelectron spectroscopy, electron energy-loss spectroscopy and Fourier transform infrared spectroscopy. X-ray diffraction (XRD) was used to characterize the powder structure. The maximum percentage of the single C-N bonding in the powder was 55%, which is close to the theoretical value and the XRD pattern indicates the powder is mainly composed of alpha-C3N4 and beta-C3N4. (C) 2003 Elsevier Science B.V. All rights reserved.