Synthesis of cerium oxynitride and oxoguanidinate at high pressures

The pursuit of novel materials with tunable properties has driven significant interest in mixed-anion compounds, such as carbon nitrides and oxynitrides. In this study, we explored the Ce-O-N-C system under pressures of 35-55 GPa and temperatures of 1500-1800 K. The introduction of oxygen into the Ce-N system resulted in the formation of a novel oxynitride, Ce4O3N4, characterized by lower-order N-N bonding compared to the triple-bonded N2 molecule. In addition, we identified a new cerium oxoguanidinate, Ce2OCN3, in the Ce-O-C-N system. The crystal structures of Ce4O3N4 and Ce2OCN3 were determined using single-crystal x-ray diffraction, and their solutions were validated through Raman spectroscopy and density functional theory calculations. This experimental approach provides a robust method for investigating mixed-anion systems under high-pressure conditions. The identification of lower-bond-order nitrogen anions in oxynitride and guanidinate anions in oxoguanidinates highlights the potential for developing novel materials with unique properties based on mixed-anion species.