Green-emitting Eu-activated powders were produced by a two-stage method consisting of pressure-assisted combustion synthesis and postannealing in ammonia. The as-synthesized powders exhibited a red photoluminescence (PL) peak located at nm when excited with nm UV. This emission peak corresponds to the5D0→7F2transition in Eu3+. After annealing in ammonia, the PL emission changed to an intense broad-band peak centered at nm, most likely produced by 4f65d1→4f7electronic transitions in Eu2+. This green-emitting phosphor has excitation band in the near UV-blue region (–450 nm). X-ray diffraction analysis reveals mainly the orthorhombic EuAlO3and Al2O3phases. Transmission electron microscopy observations showed that the grains are formed by faceted nanocrystals (~4 nm) of polygonal shape. The excellent excitation and emission properties make these powders very promising to be used as phosphors in UV solid-state diodes coupled to activate white-emitting lamps.
Morphology-Controlled Precipitation of Cerium Oxalate Crystals: The Effect of Water in Nanostructured Solvents
