Synthesis and structural characterization of a new SbPO4-GeO2 glass system

This work presents the production and characterization of a new prolific binary glass system based on SbPO 4 -GeO 2 . The dependence of GeO 2 content on thermal, structural and optical properties were investigated by means of thermal analysis , Raman, UV–Vis-NIR, infrared, M-lines and EPR spectroscopy . Glass transition temperatures remain constant around 410 °C when GeO 2 content is increased, indicating that GeO 4 units are not responsible for increasing the connectivity of PO 4 units. Thermal stability linearly increases as a function of GeO 2 content, reaching a value around 400 °C for glass containing 90 mol% of GeO 2 . Raman spectroscopy was used to evaluate the glass structural changes when GeO 2 is incorporated from 30 to 90 mol% indicating a gradual change from a phosphate to a germanate glass skeleton. The optical window extends from 350 nm at UV region, up to 2.7 μm in the middle-infrared region limited by the multiphonon cut-off due to the strong OH absorption. M-lines technique shows that increasing GeO 2 content decreases the refractive index , mainly because the lower concentration of higher polarizable antimony atoms. EPR spectra of heat treated V 2 O 5 doped glasses, at different temperatures above the glass transition temperature, shows the characteristic eight-line hyperfine splitting spectrum. The spin Hamiltonian parameters obtained from the simulated spectra indicates that the paramagnetic tetravalent vanadium ions in the glasses exist as vanadyl form VO 2+ , located in axially distorted octahedral sites. For glasses treated at higher temperatures a second VO 2+ component appears in the EPR spectra and the analysis of the spin-Hamiltonian parameters suggests that these vanadyl ions are in more tetragonal distorted octahedral sites than those in the glass. • New stable glass system SbPO 4 -GeO 2 was studied. • The structure was evaluated using Raman and EPR spectroscopies. • VO 2+ was used as a structural probe.