The origin of nanostructuring in potassium niobiosilicate glasses by Raman and FTIR spectroscopy

Study on optical properties of La2O3–TiO2–Nb2O5 glasses prepared by containerless processing

“…The peak position at 630 cm À 1 may be associated with the vibrations of NbO n polyhedra. The higher wavenumber of the band is due to the deformation of the NbO n polyhedra and the shift to higher frequencies is well documented for glassy and crystalline niobium oxides [35]. There are no significant changes of the peak at 780 cm À 1 , which could be assigned to the Ti-O-Nb chains deformation mode.…”

Effect of Niobium Oxide on the Structure and Properties of Melt‐Derived Bioactive Glasses

“…The low-frequency region of the spectrum can be observed some discreet peaks assigned to ring structures in the glass network (symmetric ring-breathing mode involving mainly oxygen motion, defects such as broken bonds in the vitreous silica network or the breathing modes of planar rings of three-and fourmembered rings). 48 Although, one can observe an increase gradually of intensity as a function of Nb 2 O 5 content, no absorption was noted at 220 or 593 cm À1 48 (see topic SM5, Fig. S7), confirming the absence of Nb-O-Nb bonds in both vitreous series studied.…”

“…49,50 For Nb-glasses a shift towards higher frequency (~650 cm À1 ) can be seen in both series, which is assigned to vibrational mode for Si-O-Si bonds coupled bending modes vibrations of Nb-O bonds in the NbO 6 octahedra with a low degree of distortion and without NBO's. 48,51,52 Furthermore, one can observe a strongest band at 800 and 810 cm À1 for series I and II, respectively, which have been related to different degree of distortion of NbO 6 octahedra 15,51 linked into chains (Nb-O-Si). Such features tend to overshadow the Si-O vibrational modes due to larger polarizability and consequent high scattering cross section of the niobate vibrating groups.…”

Effects of Zr and Ga doping on the stoichiometry and properties of niobium oxides

“…The appearance of this mode, in this high temperature region, is seen both in Ga 2 O 3 and ZrO 2 doped samples, suggesting that highly distorted NbO 6 octahedra are promoted [27]. As in the case of other niobate systems [26,28,29], the highly distorted octahedra of NbO 6 , can be caused by the presence of oxygen vacancies, which diffusion can be promoted by the high temperatures and, in this case, by the presence of the doping agents (either by the difference in ionic radius or valence). Regarding the samples HT at 900 1C, it was observed that, in most cases, different regions of the same pellet produced different spectra, which is explained by the presence of additional crystalline phases.…”