Properties of sol-gel-derived Al2O3-SiO2 glasses using Eu3+ ion fluorescence spectra

Eu3+ ion fluorescence spectra were compared in glasses of the Al2O3-SiO2 system prepared by a sol-gel process. The gels synthesized by the hydrolysis of Si(OC2H5)(4), Al(OC4H9sec)(3), and EuCl3 . 6H(2)O were heated in air from 200 to 1000 degrees C to form xAl(2)O(3) .(100-x)SiO2 (x = 0, 5, 10 mol%) glasses containing 1, 2 and 5 wt% of Eu2O3, Eu3+-doped Al2O3-SiO2 glasses had an intense fluorescence, two times larger than that of glass without Al2O3. The phonon sideband (PSB) peaks associated with the F-7(0) --> D-5(2) transition of Eu3+ ion were observed at 910 and 600 cm(-1), which were assigned to the Si-O- and Al-O- bonds, respectively, As the content ratio of Al3+ to Eu3+ ion decreases, the PSB intensities decrease and the band at 910 cm(-1) disappears in samples of 1 and 2 wt% of Eu2O3. It is concluded that Eu3+ ion is preferentially coordinated with Al-O- bonds, where Al3+ ions constitute the AlO6 octahedra.