Structural characterization and enhanced luminescence of Eu-doped 2CeO2–0.5La2O3 composite phosphor powders by a facile solution combustion synthesis
The cerium lanthanum composite 2CeO2–0.5La2O3 and rare earth Eu3+-doped composite phosphor powders were synthesized by a facile solution combustion reaction. X-ray diffraction patterns suggested Ce2LaO5.5 with a cubic fluorite structure which was the same as pure CeO2 except for the lattice parameter a. After the activator Eu3+ was doped to the composite, Eu3+ could locate at either La3+ or Ce4+ sites due to their close ionic radius. It was found that the lattice parameter a gradually decreased with increasing Eu concentration as Eu3+ occupied the La3+ site. However, the lattice parameter a obviously increased with increasing Eu concentration if Eu3+ occupied the Ce4+ site. All of the phosphor powders showed red-light emission from the dominant 5D0 → 7F2 characteristic transition of Eu3+ under excitation with 466 nm blue light. In particular, the system displayed remarkably enhanced luminescence as Eu3+ occupied the Ce4+ site rather than the La3+ site. The reason for this should be ascribed to the change in the amount of O vacancies in the host, which was confirmed from their Raman spectra. The results might be beneficial for the system potentially used in solid state lighting as well as other optoelectronic fields.