Synthesis and annealing effects on the structure of alumina by polyol mediated process

Rare-earth ion (Eu³⁺ and Tb³⁺)-doped and undoped aluminum oxide powders have been prepared via polyol mediated synthesis. The precursors were aluminium nitrate, rare-earth (RE: Tb, Eu) nitrate and diethylene glycol. The powders were generated using low-temperature (T _max ∼ 200°C) and reaction time of 150 min. By controlling the acidity of the synthesis solution and the precursor concentration, sub-micrometric aggregates (about 300 nm) with spherical morphology were obtained. The powders of RE-doped Al₂O₃ were further investigated by photon correlation laser, X-ray diffraction, transmission electron microscope, scanning electron microscope, thermal analysis and photoluminescence emission spectra. The results showed that α-Al ₂O₃ is formed at a temperature significantly lower than the solid sate reaction route. The luminescence of Al₂O₃ doped with 5 at.% Eu was observed with emission band in 614 nm and Al ₂O₃ doped with 5 at.% Tb showed an emission band in 544 nm.