Photoluminescence Properties of Lanthanide-Doped Alumina and YAG Aerogels

In this work, therange of alumina (Al2O3) and yttrium aluminum garnet (YAG) aerogelswas extended by doping them with lanthanide ions. The aerogels weresynthesized by using a universal, epoxide-assisted sol-gelmethod. They were thermally treated to induce structural changes,which were characterized in more detail by using X-ray diffractionand electron microscopy. The alumina samples showed topotactic phasetransformations from boehmite, via & gamma;-alumina to a mixed aluminaphase, while the YAG started as an amorphous mixed oxide phase, whichcrystallized at 1000 & DEG;C into pure crystalline YAG. In order toexpand the functionalities of the aerogels, they were doped with therare-earth ions Eu3+ and Tb3+ (3 mol %). Thered or green photoluminescence could be observed only starting froma temperature treatment of 550 & DEG;C, which can be related to thedefect reduction and crystallinity increase due to phase transformationsand sintering processes occurring. For the first time, the photoluminescencequantum yields of luminescent aerogels could be determined. The highestquantum yield of 25.5 & PLUSMN; 1.1% was achieved for the Al2O3-Tb-1000 sample.