Photoluminescent Properties and Local Structure of Tb Doped Fibrous Alumina

A boehmite sol which contains uniform fibrous nanoparticles has a unique property to form a film by its self-assembling properties. When Tb ions were added to the sol, the film became photoluminescent (PL) and emitted bright green light due to the f-f transition of Tb by UV irradiation. The PL intensity varied with calcination temperature during pretreatment. The best performance was obtained when the sample was treated around 800 degrees C. The PL performance normalized by the Tb content was higher for samples with a lower Tb content. Structural analysis by TEM, XRD, and XAFS revealed that when the Tb content was lower than Tb/Al = 2.5/97.5 in the atomic ratio, Tb ions were dispersed on the alumina surface isolated from each other, and those Tb species showed a high PL performance. On the other hand, for densely Tb doped samples, excessive Tb ions aggregated and formed Tb oxide nanoparticles, which were supposed to have lower PL efficiencies.