Judd-Ofelt Intensity Parameters and Optical Properties of Eu/Li Co-Doped CeO₂ Phosphor

In this work, the intense orange-red emission of Eu3+ singly and Eu3+/Li+ co-doped CeO2 phosphors synthesized by solution combustion using urea as fuel was investigated experimentally and theoretycally. X-ray diffraction and high-resolution transmission electron microscope analysis confirmed the formation of a single-phase CeO2 cubic with high crystallinity. Under 360 nm excitation, the phosphors emitted an intense orange-red region of Eu3+ as a function of Li+ doping content. Significantly, it was enhanced 12/10 times by Li+ co-doping due to the increased crystallinity of the host lattice. The energy transfer proccesse associated with cross-relaxation is responsible for decreasing the experimental lifetime of Eu3+. The influence of Li+ doping content on the characterization properties of CeO2:Eu, Li phosphors was further explained using Judd-Ofelt (J-O) theory, from which branching ratios (beta(r)), transition probability (A), radiative lifetime (tau(cal)), and stimulated cross-section (sigma(e)) emission of the phosphors were estimated. The results indicate that an effectively improved crystallinity by Li+ co-doped CeO2:Eu can significantly enhance its luminescence intensity, making it suitable for optoelectronic and display applications.