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

Abstract Eu-doped langanite nanopowders were prepared by a citrate sol–gel method and annealed in air at various temperatures between 700 °C and 1000 °C. For annealing temperatures up to 800 °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 °C (∼60% of the efficiency of the bulk material).