Synthesis, characterization and luminescent properties of novel red emitting phosphor Li3Ba2Ln3(MoO4)8:Eu3+ (Ln = La, Gd and Y) for white light-emitting diodes

Intense red emitting phosphors Li₃Ba₂Ln₃(MoO₄)₈:Eu³⁺ (Ln = La, Gd and Y) have been prepared by sol-gel method. The crystallization processes of these phosphor precursors have also been characterized by X-ray diffraction (XRD) and thermogravimetry-differential thermal analysis (TG-DTA). The properties of these resulting phosphors are characterized by photoluminescence (PL) spectra and reflectance spectra in a comparable way. In addition, environmental scanning electron microscopy (ESEM) is used to characterize the shape and size distribution of the phosphors. The results of TG-DTA and XRD indicate that all of the Li₃Ba₂Ln₃(MoO₄)₈:Eu³⁺ (Ln = La, Gd and Y) phosphors crystallize completely at about 550 °C, and they all adopt the monoclinic structure in the range of our experiments. The luminescent properties of these phosphors are also similar. The excitation (PLE) spectra of phosphors Li₃Ba₂Ln₃(MoO₄)₈:Eu³⁺ (Ln = La, Gd and Y) are mainly attributed to O → Mo charge-transfer (CT) band at about 295 nm and some sharp lines of Eu³⁺ transitions in near-UV and visible regions, and the two strongest absorption lines at 395 nm and 465 nm are comparative. For all of Li₃Ba₂Ln₃(MoO₄)₈:Eu³⁺ (Ln = La, Gd and Y) phosphors, intense red emissions peaked at 616 nm assigned to ⁵D₀ → ⁷F₂ transition of Eu³⁺ are obtained under the excitation of ∼394 nm and ∼465 nm light, which indicates that these phosphors may serve as potential red phosphor candidate for near-UV and blue LEDs.