Bonding and Structure of Oxofluoroniobate-Based Glasses

Abstract

Glasses based on the oxofluoroniobate anion have been characterized by vibrational and solid-state NMR spectroscopy. The mechanism of glass formation in the systems K2NbOF5-MF3 (M = Al, In) has been suggested. A glass network is built from the chains of corner-sharing octahedra through -Nb-F(O)-M- and -Nb-F-Nb- bridges. Isolated NbOF5(2-) octahedra are also present, which is consistent with the glass composition. The high ionic mobility of NbOF5(2-) due to its fast reorientations results in equalization of the Nb-O and Nb-F distances, which is reflected in the appearance of the IR band at 700-800 cm(-1) not observed in the Raman spectrum. Its assignment to bridging -Nb-O-Nb- species accepted in the literature was not proven.

Inorganic Pillar Center-Facilitated Counterdiffusion Synthesis for Highly H2 Perm-Selective KAUST-7 Membranes

“…The FT-IR spectra of NiNbOF 5 , NiO, Nb 2 O 5, and KAUST-7 powders are shown in Figure . Both the NiNbOF 5 and KAUST-7 samples respectively exhibited characteristic absorption peaks at 553 and 944 cm –1 assigned to Nb–F and Nb-terminal O stretching vibration in the (NbOF 5 ) 2– octahedron, while Nb 2 O 5 almost did not do. The reason was that the structure of NiNbOF 5 was extremely close to KAUST-7 while the Nb–O bond in Nb 2 O 5 was different from NiNbOF 5 .…”

“…The FT-IR spectra of NiNbOF 5 , NiO, Nb 2 O 5, and KAUST-7 powders are shown in Figure 2. Both the NiNbOF 5 and KAUST-7 samples respectively exhibited characteristic absorption peaks at 553 and 944 cm −1 assigned to Nb−F and Nbterminal O stretching vibration in the (NbOF 5 ) 2− octahedron, 35 was assigned to the presence of Ni 2+ in the nickel salt 36,37 and the minor peak at 864.0 eV (2p 3/2 ) could be assigned to NiO. 38 The major peak observed in the Ni 2p 3/2 of KAUST-7 moved right compared to NiNbOF 5 , which was due to the coordination of Ni 2+ with pyrazine.…”

Transparent oxyfluoride glass ceramics

“…Therefore, in order to resolve that latter lasing problem, one has to find the new glass compositions that would not have areas of phase separation (aliquation) with fluorides. Already, there are numerous classes of oxyfluoride glasses that should be thoroughly M a n u s c r i p t 37 investigated from this point of view [347][348][349][350]357] in order to develop new types of oxyfluoride glass ceramics.…”