A STUDY OF THE STRUCTURAL EVOLUTION OF THE SOL-GEL DERIVED SM3-DOPED SILICA GLASS()

Sm3+-doped silica gels have been prepared by a sol-gel process using t etraethyl orthosilicate, H2O, HCl and Sm(NO3)(3) . 6H(2)O. The structu ral evolution and densification behaviour of the gels during thermal t reatment have been monitored by physical property measurements, visibl e-MR, IR and fluorescence spectroscopy. The gels show a continuous den sification and strengthening of the silica network with increasing hea t-treatment temperatures (60-100 degrees C). The fluorescence intensit y ratio of the (4)G(5/2) --> 6H(9/2) to (4)G(5/2) --> H-6(5/2) transit ion has been used to study the change of Sm3+ environment during gel-g lass conversion. Samarium passes through three different environments at different heat-treatment temperatures during gel to glass conversio n.