The effect of alkaline earth metallic ions on the photoluminescence properties of sol-gel silica glass

Mg2+-, Ca2+-, Sr2+- and Ba2+-doped silica glasses have been prepared using sol-gel processing by employing Si(OC2H5)4, MgCl26H2O, CaCl22H2O, SrCl26H2O and BaCl22H2O as precursors, with HCl as a catalyst. The UV–visibleabsorption spectra of the doped samples are almost the same as those of the undoped sample. The absorption bands of alkaline earth metallic ions have not been observed in the doped samples. Strong visible light has been observed from sol- gel silica glasses doped with alkaline earth metallic ions. The relative fluorescence intensity of the Sr2+-doped (the impurity mole ratio of Sr2+ was 0.268%) and the Ba2+-doped (the impurity mole ratio of Ba2+ was 0.448%) samples was about 4 times that of the undoped sample. The relative fluorescence intensity of the Mg2+-doped (the impurity mole ratio of Mg2+ was 0.069%) sample was about 2.5 times that of the pure glass sample. The relative fluorescence intensity of the Ca2+- doped (the impurity mole ratio of Ca2+ was 0.179%) sample was about 3 times that of the pure glass sample. Alkaline earth metallic ions affect the formation and conversion of luminescent defects in sol-gel silica glass. Thus, the relative fluorescence intensity of the doped samples increases more than that of the undoped sample.