Luminescence of Eu-doped langanite nanopowders synthesized by a citrate sol-gel method

Eu-doped langanite nanopowders were prepared by a citrate sol-gel method and annealed in air at various temperatures between 700 degrees C and 1000 degrees C. For annealing temperatures up to 800 degrees C, only the langanite phase is observed. For higher annealing temperatures, part of the langanite powder transforms in perovskite (LaGaO(3)), as evidenced in both XRD and luminescence spectra. Regardless the annealing temperature, the lifetime of (5)D(0) remains close to 1 ms. The reddish color of the powders due to color centers associated to oxygen defects intensifies with increasing annealing temperature. The best efficiency of the Eu-langanite nanopowders was obtained for the sample annealed at 700 degrees C (similar to 60% of the efficiency of the bulk material). (C) 2010 Elsevier B.V. All rights reserved.