Structural characterization and enhanced luminescence of Eu-doped 2CeO2–0.5La2O3 composite phosphor powders by a facile solution combustion synthesis

Abstract

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 Ce₂LaO_5.5 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.