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 °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 (LaGaO3), as evidenced in both XRD and luminescence spectra. Regardless the annealing temperature, the lifetime of 5D0 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).

Research highlights▶ For annealing temperatures up to 800 °C, only the langanite phase is observed. ▶ For annealing temperatures above 800 °C, part of the langanite transforms in LaGaO3. ▶ The red color of the LGN powder intensifies with increasing annealing temperature. ▶ Best efficiency of the emission obtained for the sample treated at 700 °C. ▶ Lifetime of 5D0 is in the millisecond range, regardless the annealing temperature.