Structure and properties of MoO3-containing zinc borophosphate glasses

Abstract

a b s t r a c tZnO-B 2 O 3 -P 2 O 5 glasses doped with MoO 3 were investigated in the series (100Àx)[0.5ZnO-0.1B 2 O 3 -0.4P 2 O 5 ]-xMoO 3 , where bulk glasses were obtained by slow cooling in air within the compositional region of 0 6 x 6 60 mol% MoO 3 . The incorporation of MoO 3 into the parent zinc borophosphate glass results in a weakening of bond strength in the structural network, which induces a decrease in chemical durability and glass transition temperature. Raman spectra reflect the incorporation of molybdate groups into the glass network of the studied glasses by the presence of the polarized vibrational band at %976 cm À1 ascribed to the MO x symmetric stretching vibrations and the depolarized band at %878 cm À1 ascribed to the Mo-O-Mo stretching vibration. The incorporation of molybdate units into the glass network results in the depolymerization of phosphate chains and the formation of P-O-Mo bonds, as reflected in Raman and 31 P NMR spectra. According to the 11 B MAS NMR spectra, tetrahedral B(OP) 4Àx (OMo) x units are formed in the glasses, whereas only a small amount of BO 4 units is converted to BO 3 units in the MoO 3 -rich glasses.

Glass-forming ability and structure of ZnO–MoO3–P2O5 glasses

“…This is similar to the structure found in sodium phosphomolybdates [14]. Simultaneously, with increasing MoO 3 content a band at 884 cm − 1 appears in the Raman spectra, which shows on the formation of Mo-O-Mo bridges between MoO 6 octahedra [6,14,25]. This band broadens and shifts to lower wavenumbers in glasses with more than 50 mol% MoO 3 , which can be caused by the formation of three-dimensional clusters composed of several MoO 6 octahedra interconnected by common edges.…”

“…This conclusion was made on the basis of the absence of Raman band at 884 cm − 1 (Fig. 7), ascribed to the vibrations of Mo-O-Mo bonds [6,14,25]. We suppose that the structure of this glass is built up of phosphate chains interconnected by bridging oxygens or by -O-Mo-Obridges of MoO 6 octahedra as well as in Mo 2 O 2 P 4 O 13 [32].…”

“…We assume that the band at 976 cm − 1 should be ascribed to the symmetric stretching vibration of MoO 6 tetrahedra, rather than to the vibrations of Mo-O or Mo O bonds only [7,14]. Characteristic spectral features of phosphate units decrease in intensity with increasing MoO 3 content due to a much higher Raman scattering efficiency for Mo-O vibrations than that for P-O vibrations [25]. A high Raman scattering efficiency of the vibrations of molybdenum species is reflected by a rapid increase in the intensity of bands at ∼968 and ∼896 cm − 1 within the concentration region of 0-40 mol% MoO 3 .…”

Structure and dielectric constant of silver molybdophosphate mixed network former glasses

“…The spectra reveal different characteristic absorption bands corresponding to different vibration modes of phosphate and molybdate units. The bands in the region 1100-1250 cm −1 , 990-1050 cm −1 , 880-920 cm −1 and 680-740 cm −1 are assigned to the asymmetric stretching vibration of P O bond, asymmetric stretching vibration of P-O − mode, asymmetric stretching mode of P-O-P bond and symmetric stretching of P-O-P bond respectively [28][29][30][31]. The band observed around 750-840 cm −1 for glasses containing MoO 3 is assigned to the stretching vibration of MoO 4 2− anions [35].…”

“…A few studies of compositional dependence glass network structure in a few molybdophosphate glasses show that the increase of MoO 3 content leads to the transformation of Mo-O − and P O bonds into Mo-O-Mo and weaker Mo-O-P bridging bonds [28,29]. In zinc phosphate and borophosphate glasses [30,31] it has been observed that the incorporation of MoO 3 increases the depolymerization of phosphate chains and a gradual transformation of metaphosphate into diphosphate and orthophosphate units occurs. The Raman spectroscopic study of these glasses reveals that the ratio of MoO 6 /MoO 4 increases with increasing content of MoO 3 [32,33].…”