Improved morphology and optimized luminescence of Eu3+-doped La2Ce2O7 composite nanopowders by surfactant-assisted solution combustion synthesis

In this paper, the red-emitting La₂Ce₂O₇:Eu³⁺ composite nanopowders were successfully prepared via simple solution combustion synthesis (SCS) and surfactant (polyvinyl alcohol)-assisted solution combustion synthesis (PVACS), and characterized by X-ray diffraction, scanning electron microscopy, photoluminescence emission and excitation spectra, as well as fluorescent decay measurements. The X-ray diffraction results suggested the formation of La₂Ce₂O₇ composite solid solution, and the introduction of Eu had little influence on the structure of the composite. The La₂Ce₂O₇:Eu³⁺ composite showed controlled nanopowders (from 10 to 120 nm) with well-distributed morphologies under the assistance of certain amount of surfactant and subsequent heat-treatment process. The photoluminescence measurements indicated that the samples could be efficiently excited with blue light (467 nm), and exhibited the characteristic red emission of Eu³⁺ ion at 616 nm corresponding to the ⁵D₀ →⁷F₂ transition. The optimal concentration of activator Eu³⁺ ion was confirmed at about 15 mol% as the total amount of cations was considered. Moreover, the relative emission intensity, fluorescent lifetime and quantum efficiency of the La₂Ce₂O₇:Eu³⁺ composite powders prepared by PVACS were compared with those achieved by simple SCS and traditional solid state reaction, which further confirmed the merits by PVACS. These results may facilitate the optimized composite nanopowders as a potential candidate for solid state lighting owing to the coincidence of 467 nm excitation light with the emission of InGaN chips in white light-emitting-diodes.