The complex Raman response of cations in alumino-silicate glasses

International audienceRaman scattering of ternary alumino-silicate glasses with alkali and alkaline-earth cations(M=Mg, Ca, Sr, Ba, Na,...) has been performed. The concentrations range from the peral-caline (MO/Al2O3> 1) to the peraluminate (MO/Al2O3< 1) domain keeping constant thesilica content. The vibrational signature of the cations is clearly evidenced at low frequencyin the depolarized (VH) spectra. Between one and three bands are identifed. They associate to different types of motions depending on the charge carried by the cation (alkali oralkaline-earth atoms). In addition, glasses with magnesium exhibit a very peculiar behavior.Very interestingly, some bands disappear for the tectosilicate glasses (MO/Al2O3=1) andin the peraluminate domain revealing a clear vibrational contrast between network modifer cations and charge compensator cations. A preliminary experiment in a quaternaryalumino-silicate system combining two types of alkali atoms highlights the possibility by sim-ple Raman spectroscopy to define the preferential role of each cation, i.e. network modieror charge compensator, and to make a semi-quantitative treatment as well