Crystal Structures of Three Polymorphs of Cs3ScF6 by Means of Solid-State NMR, X-Ray, and Neutron Diffraction

https://doi.org/10.1021/acs.cgd.4c01598

Three polymorphs were found to exist for Cs₃ScF₆ in the room temperature range of up to 280 °C. Two phase transitions were identified by differential scanning calorimetry (DSC) analyses at 92 and 196 °C upon heating. In situ high-temperature solid-state NMR, synchrotron and laboratory X-ray diffraction, and neutron powder diffraction were used for structural characterization. The crystal structure of the high-temperature (γ) phase adopts the cubic Fm3̅m (Z = 4) space group with a = 9.6048(7) Å at 250 °C. The other two polymorphs, α and β, have tetragonal symmetry with space groups I4₁/a (Z= 80) and I4/m (Z= 10), and lattice parameters are a = 21.15222(6) Å, c = 38.21648(8) Å and a = 15.0401(2) Å, c = 9.6341(2) Å at RT and 150 °C, respectively.