Synthesis of Cerium Tetrafluoride and Cerium Trifluoride Nanoscale Polycrystals from Ammonium Hydrogen Difluoride

This paper reported a dry synthesis and characterization of cerium tetrafluoride (CeF4) and cerium trifluoride (CeF3) nanoscale polycrystals (NPs). The CeF4 NPs were spherical or flaky and approximately 10 ± 2 nm in diameter. The CeF3 NPs were rod-shaped nanorods with a length of about 150 ± 5 nm and a diameter of about 20 ± 2 nm. The first step was to synthesize the intermediate product-(NH4)4CeF8 by mixing CeO2 and NH4HF2 at a molar ratio of 1:6 at 390 K. The structural characterization was analyzed by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Then, (NH4)4CeF8 was heated in an argon gas flow to synthesize the CeF3 and CeF4 NPs. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The properties of CeF3 and CeF4 NPs were further evaluated by transmission electron microscopy (TEM), selected area electron diffraction pattern (SAED), and high-resolution transmission electron microscopy (HRTEM). The findings provided an alternative strategy for the synthesis of nanometer fluorides, which could be a reference for high-performance research on other nanometer fluorides.