Brillouin scattering study of binary potassium germanate glasses

The glass samples were prepared in the series xK2O–(100 − x)GeO2 with 0 < x < 27.0, where x denotes the K2O mol%, by the solution method with high homogeneity. Brillouin spectroscopy has been performed for potassium germanate glasses with increasing alkali contents. The sound velocities and the elastic moduli were measured by Brillouin scattering in 90 A scattering geometry. Acoustic velocities for both longitudinal and transverse wave, Debye velocity, elastic moduli and Debye temperatures have been determined with all K2O mol% contents. Each property shows its maximum at about 15 mol% K2O content. This indicates that about 15 mol% K2O content provides the maximum sound velocity. It has been found that the glass transition temperatures are related to the Debye temperatures.