The Nuclear Magnetic Shielding of the ¹⁹F-Nuclei in KZnF₃

Abstract

Using solid state multiple pulse techniques the magnetic shielding tensors σ of the 19F nuclei in a single crystal of KZnF3 have been measured. The F--site symmetry in KZnF3, D4h , allows axial anisotropy of σ and determines fully the principal shielding directions. Using CaF2 as the reference compound, the average shielding is + 85 ppm and the shielding anisotropy is + 18.4 ppm. These results are discussed in terms of shielding contributions from (a) the closed shell electrons of the F--ion whose shielding is considered, (b) the closed shell electrons of the neighbouring metal and fluorine ions and (c) weak admixture of covalency to the predominantly ionic Zn++-F- bonding.

Phase Separation and Nanocrystallization in KF–ZnF2–SiO2 Glasses: Lessons from Solid-State NMR

“…Comparing these to the documented 19 F chemical shift values for KF (−133 ppm) and ZnF 2 (−206 ppm), the signals at −126 and −140 ppm may be assigned to fluorine nuclei that are predominantly coordinated by K + ions (FK 6 -polyhedra as in KF (rock salt structure)), whereas the signal at −200 ppm may be traced back to FZn 3 -units as in ZnF 2 (rutile structure). We note that the broad signal at −200 ppm may also contain contributions from FZn 2 K 4 -environments as in KZnF 3 (perovskite structure), the signal of which has been found at −193 ppm . Annealing to 540 °C/10 h entails considerable sharpening of the −200 ppm signal, and the contributions from KZnF 3 and ZnF 2 are now clearly separated.…”

“…We note that the broad signal at −200 ppm may also contain contributions from FZn 2 K 4 -environments as in KZnF 3 (perovskite structure), the signal of which has been found at −193 ppm. 35 Annealing to 540 °C/10 h entails considerable sharpening of the −200 ppm signal, and the contributions from KZnF 3 and ZnF 2 are now clearly separated. Annealing to 580 °C/10 h induces drastic changes to the 19 F spectrum with new signals occurring at −152, −157, and −174 ppm.…”

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. , …”