Bonding and Structure of Oxofluoroniobate-Based Glasses

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

Synthesis, Structural, Magnetic, and Electronic Properties of Cubic CsMnMoO₃F₃ Oxyfluoride

A powder sample of CsMnMoO₃F₃ oxyfluoride has been prepared by solid state synthesis. The pyrochlore-related crystal structure of CsMnMoO₃F₃ has been refined by the Rietveld method at <i>T</i> = 298 K (space group <i>Fd-</i>3<i>m</i>, <i>a</i> = 10.59141(4) Å, <i>V</i> = 1188.123(8) ų; <i>R</i>_B = 3.44%). The stability of the cubic phase has been obtained over the temperature range <i>T</i> = 110–293 K by heat capacity measurements. Magnetic properties have been measured over the range of <i>T</i> = 2–300 K. The electronic structure of CsMnMoO₃F₃ has been evaluated by X-ray photoelectron spectroscopy. Chemical bonding effects have been discussed for all metal ions using binding energy difference parameters and wide comparison with related oxides and fluorides. The competition between O^2– and F^– ions for metal valence electrons has been found