Photoluminescence characteristics of SiO2-GeO2-R2O (R: Na, K, Rb, and Cs) glasses

This study fabricates 50SiO2・50GeO2 and 50SiO2・(50-x)GeO2・xR2O (R: Na, K, Rb, and Cs, x = 5?40) glasses using the conventional melt-quenching method. Their photoluminescence characteristics were investigated by measuring their emission and excitation spectra. In the case of the 50SiO2・50GeO2 glass, a sharp and significant emission band attributed to the Ge2+ center appeared prominently at a central wavelength of 395 nm, corresponding to an excitation band at 250 nm. However, the emission spectra of 50SiO2・(50-x)GeO2・xR2O glasses revealed distinct emission bands around 480 and 540 nm, which differ from the 395 nm emission band typically associated with the Ge2+ center. These emission bands indicated coordination of the Ge2+ center with alkali ions. The basicity of alkali oxide, which is linked to its ability to provide O2? ions, influenced the coordination of the Ge2+ center with alkali ions in the glasses, resulting in a decrease in the amount of coordination. Consequently, the intensity of the emission bands varied depending on the quantity and type of alkali components present.