Structure and luminescence properties of porous alumina templates doped with rare earth elements and transition metals

We propose to develop phosphor materials on the basis of porous alumina templates doped with rare earth elements and transition metals. This issue is especially important in connection with the development of random lasers, since the scattering properties of the porous template can de controlled by tailoring its morphology. In this work, we demonstrate that, apart from the morphology, the crystallographic structure of the template can be controlled by the conditions of post-anodization thermal treatment applied for the activation of the impurity impregnated from rare earth or transition metal containing solutions. The initially amorphous alumina structure is transformed into a γ-Al2O3 phase by annealing at 300–700°C. A δ-Al2O3 phase is predominant in samples annealed at 800–1000°C. The samples annealed at temperatures above 1100°C exhibit an α-Al2O3 structure. The technological conditions related to the solution concentration and duration of impregnation, postimpregnation annealing temperature and annealing duration were optimized from the point of view of maximum impurity ion activation.