Raman and infrared spectroscopic investigation of GeO2-modified K2Si2O5 glasses synthesized by Sol–gel and standard melting methods

Abstract

Two approaches for producing potassium–germanium silicate amorphous materials are presented: the conventional batch melting method followed by melt quenching, and a sol–gel synthesis route followed by melting in a furnace. Potassium disilicate glasses modified by germanium oxide are synthesized using both presented methods. The structures of the obtained glasses are examined using vibrational spectroscopy techniques, including infrared and Raman spectroscopy. The analysis of bands in the high-frequency region of the Raman spectra suggests a structurally uniform network at the short-range level. The features of germanium distribution within the silicate matrix were derived from data on [4] Ge–O– [4] Ge bond vibrations, which are localized in the low-frequency region of the spectrum (400–650 cm⁻¹) similarly to Si–O–Si bonds. The spectral analysis identified all possible coordination states of germanium in the materials, [4] Ge, [5] Ge, and [6] Ge, as well as three- and four-membered rings. Infrared spectroscopy was used to confirm the structural features of the glasses obtained via the modified sol–gel method compared to the conventional melt-quenching technique. The systematic changes in the line shapes associated with Si–O–Si and [4] Ge–O– [4] Ge vibrations in samples synthesized from TEOS are likely related to a more homogeneous distribution of germanium atoms within the germanosilicate network when addition takes place at the gelation stage.