Morphology control of phase-separation-induced alumina-silica macroporous gels for rare-earth-doped scattering media

Phase-separation behavior in the sol−gel system of alumina−silica (Al2O3−SiO2) in the presence of poly (ethylene oxide) has been investigated. Amorphous gels with interconnected macropores can be obtained from the starting composition containing up to 10 mol % Al3+ by inducing phase separation parallel to the sol−gel transition. SmCl3·6H2O is added to the present system to yield Sm3+-doped macroporous gels. The sintered Al2O3−SiO2 macroporous glasses doped with Sm3+ exhibit the photoluminescence due to the 4f−4f transition of Sm3+, and the intensity of fluorescence increases with increasing Al3+ content. The reduction of Sm3+ to Sm2+ is accomplished in Al2O3−SiO2 macroporous glasses by heat treatment in a reducing atmosphere.