Luminescent characteristics of Eu²⁺/Li⁺ doped (La-Al)₂O₃ phosphors and PMMA films activated with them

The effect of Li co-doping on the blue luminescence of Eu²⁺ doped (La-Al)₂O₃ phosphors and its incorporation into poly (methyl methacrylate) PMMA films are reported. The phosphors were synthesized by a simple two-step process in which the (La-Al)₂O₃ powders were obtained by an evaporation method, and the subsequent co-doping with Li⁺ and Eu²⁺ were made through a solid state reaction in a reductive atmosphere at 1250°C. The incorporation of those phosphors into PMMA matrix and the synthesis of films with thicknesses between 6 and 12 μm was made by drop-casting. The characteristic blue broad band emission centered at 440 nm associated with the 4f⁶5d¹ →4F⁷ transition of Eu²⁺ ions (CIE coordinates 0.6731, 0.3343) was observed when these powders were excited with 297 nm light. These luminescence intensity was enhanced when Li⁺ was incorporated as co-dopant up to 320% with respect to those phosphors without Lithium. The luminescent characteristics of these phosphors were preserved when they were embedded into the PMMA films.