Crystallization, phase transition and optical properties of the rare-earth-doped nanophosphors synthesized by chemical deposition

The structural and electronic properties of Eu3+-doped Y2O3 films coated on spherical alumina nanoparticles are studied using transmission electron microscope, x-ray diffraction, and laser spectroscopic techniques. It is observed that the coated films crystallize at temperatures higher than 600°C and may be completely converted into a cubic Y2O3 nanocrystalline layer at 750°C. At 900°C, phase transition occurs between the outer coating layer and the inner core, and different types of crystalline nanophase can be obtained. In the materials that we prepared and studied, all possible crystallographic phases, including two of solid-state laser media, YAlO3 (YAP), and Y3Al5O12 (YAG), may be formed in the pseudo-binary Al2O3–Y2O3 nanosystem by controlling thermal annealing procedures from 600 to 900°C, a temperature region far below the conventional solid-state reaction temperature. The spectroscopic properties of Eu3+ in all the nanophases are characterized in comparison with those of their bulk counterparts.