Elaboration and structural characterization of silicophosphate glasses (SiO2-P2O5) synthesized via the sol-gel method

Abstract

Silicophosphate (SiO 2 –P 2 O 5 ) glasses are attractive materials for biomedical, photonic, microelectronic, and energy-related applications owing to their tunable network structure and physicochemical properties. In the present work, undoped silicophosphate glasses with the composition (100 − x) SiO 2 –x P 2 O 5 (x = 10 mol. %) were synthesized via the sol–gel method to investigate the influence of gelation time (17–20 days) on the structural evolution of the glass network. The synthesized samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. XRD patterns confirmed that all samples remained fully amorphous throughout the investigated gelation period, while quantitative analysis revealed a gradual shift of the broad amorphous halo toward lower diffraction angles accompanied by an increase in the full width at half maximum (FWHM), indicating subtle modifications in the short-range atomic arrangement without crystallization. FTIR analysis identified the characteristic vibrational bands associated with Si–O–Si, Si–O–P, P–O–P, Si–O, hydroxyl groups, and molecular water. Progressive changes in the band positions and intensities demonstrate that increasing gelation time promotes the condensation of silanol and phosphanol groups, enhances network connectivity, reduces residual hydroxyl and adsorbed water species, and induces structural relaxation within the silica–phosphate network. These results establish a clear relationship between gelation time and the short-range structural evolution of sol–gel-derived silicophosphate glasses, demonstrating that gelation time is an effective processing parameter for tailoring the glass network while preserving its amorphous nature. The structural framework established in this study provides a basis for future investigations correlating network evolution with the optical, bioactive, and transport properties of silicophosphate glasses.