PHONON SIDE-BAND SPECTRA AND LOCAL-STRUCTURE AROUND EU3+ IONS IN SODIUM-SILICATE GLASSES

The local structure around Eu3+ ions in sodium silicate glasses was investigated by the phonon sideband associated with 5D2 --> F-7(0) transition of Eu3+. Since the shapes of the electronic transition were asymmetric due to the Stark splitting of 5D2 level, the spectra were analyzed by assuming the superposition of the Gaussian distributions of phonon energy and coordination of non-bridging oxygen of the Q(n) (n = 3, 2, 1) unit in silicate glass. The phonon energy almost corresponded to those of the stretching vibrations of Q(n) units by Raman spectra. The type and fraction of the Q(n) units coordinating Eu3+ varied with alkaline content. The compositional variations of Q(n) units were similar to those determined by NMR for undoped alkaline silicate glasses. It is shown that the local structure around Eu3+ is affected by the composition of matrix glass and the phonon sideband analysis can become a powerful technique to estimate the local distribution of Q(n) in silicate glasses.