Low temperature synthesis of LnOF rare-earth oxyfluorides through reaction of the oxides with PTFE

A low temperature solid-state synthesis route, employing polytetrafluoroethylene (PTFE) and the rare-earth oxides, for the formation of the LnOF rare-earth oxyfluorides (Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), is reported. With the exception of LaOF, which forms in a tetragonal variant, rhomobohedral LnOF is found to be the major product of the reaction. In the case of PrOF, a transition from the rhombohedral to the cubic fluorite phase is observed on heating in air to 500 °C. X-ray diffraction shows the expected lanthanide contraction in the lattice parameters and bond lengths. Magnetic susceptibility measurements show antiferromagnetic-like ordering in TbOF, Tm = 10 K, with a metamagnetic transition at a field μ0Ht = 1.8 T at 2 K. An antiferromagnetic transition, TN = 4 K, is observed in GdOF. Paramagnetic behavior is observed above 2 K in PrOF, NdOF, DyOF, HoOF and ErOF. The magnetic susceptibility of EuOF is characteristic of Van Vleck paramagnetism.

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► Low temperature synthesis of LnOF rare-earth oxyfluorides from Ln2O3 and PTFE (CF2).
► Rhombohedral LnOF is the major phase and forms as nanocrystals, 29–103 nm.
► Expected lanthanide contraction observed in lattice parameters and bond lengths.
► TbOF orders antiferromagnetically at 10 K and has a metamagnetic transition at 1.8 T.
► GdOF orders antiferromagnetically at 5 K, other LnOF are paramagnetic.