The structure of potassium germanate glasses as revealed by Raman and IR spectroscopy

Raman and infrared spectroscopy were used to determine the structure of glasses for compositions xK(2)O-(100-x)GeO2, where x = 0, 10, 20, 30 40 mol%. Curve-fitting was applied to both medium- and high-frequency regions of the Raman spectra, and the main structural species formed in the system were defined. It was shown that the maximum of Ge(IV) -> Ge(VI) conversion occurs at a composition of about 20 mol% K2O. A further increase of modifier cation in glasses results in a decrease in the coordination number of Ge atoms. At the same time, there is a depolymerisation of the three-dimensional disordered network and formation of tetrahedra [GeO4] with one and two non-bridging oxygen atoms.