INFRARED REFLECTIVITY SPECTROSCOPY OF NITROGEN-SUBSTITUTED ALKALINE-EARTH ALUMINOSILICATE GLASSES

Infrared reflectivity spectra of the series M(0.37)Si(0.53)Al(0.10)O(1 .58-3x/2)N(x) with M = Mg, Ca and Ba and x varying between 0 and 0.09 are reported. The far-infrared vibrational frequency of the M cation m ainly depends on cationic mass. In the case of magnesium, the vibratio nal frequency is also sensitive to the coordination implying the glass -former (tetrahedral) or glass-modifier (likely octahedral). The anion ic effective charge measured from the Coulombic contribution to the in frared reflection bands is smaller in nitrogenated glasses than in oxi de glasses, showing an increased average bond hybrization, consistent with hardening of the structure indicated by macroscopic properties.