Fabrication of Sm2+-doped macroporous aluminosilicate glasses with high alumina content

Macroporous Al2O3–SiO2 glasses doped with Sm2+ have been prepared from a sol–gel system containing aluminum sec-butoxide, tetramethoxysilane, samarium chloride hexahydrate, poly(ethylene oxide), nitric acid, and water. Monolithic gels having interconnected macropores and skeletons are formed by inducing the phase separation parallel to the gelation. The use of aluminum sec-butoxide preheated at 80 °C as the starting material enables the incorporation of Al3+ into the gel skeleton up to 20 mol% in cation ratio. The maximum amount of Al3+, i.e., 20 mol%, is twice as large as that reported in our previous study, where aluminum sec-butoxide was diluted with sec-butanol prior to the hydrolysis. Heat-treatment of Sm3+-doped 20AlO3/2 · 80SiO2 macroporous glass under the reducing atmosphere converts Sm3+ to Sm2+, which is confirmed by the appearance of intense emission peaks attributed to 4f–4f transitions of Sm2+.