Synthesis, characterization and luminescent properties of novel red emitting phosphor Li 3Ba 2Ln 3(MoO 4) 8:Eu 3+ (Ln = La, Gd and Y) for white light-emitting diodes

Abstract

Intense red emitting phosphors Li 3Ba 2Ln 3(MoO 4) 8:Eu 3+ (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 Li 3Ba 2Ln 3(MoO 4) 8:Eu 3+ (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 Li 3Ba 2Ln 3(MoO 4) 8:Eu 3+ (Ln = La, Gd and Y) are mainly attributed to O → Mo charge-transfer (CT) band at about 295 nm and some sharp lines of Eu 3+ transitions in near-UV and visible regions, and the two strongest absorption lines at 395 nm and 465 nm are comparative. For all of Li 3Ba 2Ln 3(MoO 4) 8:Eu 3+ (Ln = La, Gd and Y) phosphors, intense red emissions peaked at 616 nm assigned to 5D 0 → 7F 2 transition of Eu 3+ 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.