1 9F shielding anisotropy in RbCaF3

Abstract

Methyl fluoride-1 3C in nematic liquid crystals: Anisotropy of the indirect 1 3C-1 9F spin-spin coupling and of the 1H, 1 3C, and 1 9F chemical shieldings A 19F NMR multipulse measurement of the chemical shift in a single crystal of cubic RbCaF 3 gave -47.0 ± 3 ppm as the isotropic value with respect to C 6 F 6 , and 128.7 ± 6 ppm as the anisotropy. The shielding is accounted for by the usual diamagnetic and paramagnetic ionic overlap and covalent terms. As a result, the Ca + + -F-bond is estimated to be 98% ionic. No significant spectral changes were found when the crystal was cooled below the cubic to tetragonal phase transition temperature. Reasons for this are given.

Solid-State NMR and NQR Spectroscopy of Lead-Halide Perovskite Materials

“…The occasional use of 19 F NMR to characterize hybrid LHPs can also be found in refs and . We also note that 19 F solid-state NMR has been applied to numerous metal fluoride perovskites (ABF 3 ) − and 2D fluoride perovskites, where A = Li, Na, K, Cs, Rb, and ammonium (NH 4 + ) and B = Mg, Ca, Ba, Sr, Mn, Co, Zn, and Ho, to study diverse materials aspects, such as fluoride ion mobility or the material’s paramagnetism. , …”

Formation and Elimination of Anti-site Defects during Crystallization in Perovskite Ba1–xSrxLiF3

“…In Figure 5, in the two left columns, static 19 F NMR spectra of nanocrystalline (mechanosynthesized) and microcrystalline (annealed) BaLiF 3 recorded at different temperatures are shown. The static 19 F NMR spectrum consists of three NMR lines, which was also observed for RbCaF 3 48 and RbPbF 3 49 and is probably caused by chemical shift anisotropy (the 19 F MAS NMR spectrum, recorded with ν rot = 60 kHz, displays a single NMR line at 66 ppm for all BaLiF 3 samples prepared 26 ). The spectra exhibit only subtle changes with temperature.…”

Mechanochemical synthesis and order–disorder phase transition in fluoride ion conductor RbPbF3

“…The 19 F NMR below 160 K corresponding to the rigid lattice showed a broad and asymmetric spectrum. The origin of this asymmetry was tentatively assigned to the chemical shift anisotropy because similar large anisotropy on 19 F NMR, ranging more than 100 ppm, has been reported for cubic perovskites such as RbCaF 3 [21]. The narrowing phenomenon far below ambient temperature, around 200-240 K, suggested the high ionic conductivity of this phase, since motional narrowing occurs when the diffusion hopping times τ becomes shorter than inverse line width [22].…”