Synthesis of carbon nitride crystals at high pressures and temperatures

Carbon nitride crystals have been synthesized from C₃N₄H₄ in the presence of a nickel-based alloy or cobalt as a catalyst at high pressure of 7 GPa and temperature of about 1400 °C. Scanning electron microscopy showed rod-like, well-faceted crystals with size of several micrometers, and the N content in these carbon nitride crystals was 47–62%. X-ray diffraction indicated the crystals were composed of α–C₃N₄ and β–C₃N₄. The experimental lattice constants of α–C₃N₄ (a = 6.425 Å, c = 4.715 Å ) and β–C₃N₄ (a = 6.419 Å, c = 2.425 Å ) agree with ab initio calculations very well.