Optical phonon spectra of lutetium fluoride,oxyfluoride, and lutetium oxide nanoparticles

Nano-and microcrystalline LuF₃ phases have been synthesized with particle sizes of 30 nm and 30 μm, respectively. Analysis of the IR reflection spectra measured at T = 300 K showed that the nanophase differs from the microcrystalline phase by reduced optical phonon frequencies. It is established that annealing of the LuF₃ nanophase in air leads to the formation of nanoparticles of the LuO_{1 ? x} F_{1 + 2x} and Lu₂O₃ compositions. The IR reflection spectra of the nanophases indicate that these nanoparticles consist of an oxyfluoride core surrounded with a Lu₂O₃ shell; the latter is in the strained state.