Development of a novel Eu3+-doped tantalate red-emitting phosphor for w-LEDs application

Two novel phosphors LiBa_4(1‒x)Eu_4xTa₃O₁₂ (H-LBTO:xEu³⁺) and Li_0.25Ba_1‒xEu_xTa_0.75O₃ (C-LBTO:xEu³⁺) were prepared successfully by a molten salt method. The transformation between these two structures was realized by changing the sintering temperature or changing the Eu³⁺ ions concentration, which was also demonstrated by the X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectra (DRS), and photoluminescence excitation (PLE) analyses. Both the sintering temperature and the Eu³⁺ ions doping concentration have significant impact on the formation of the crystal phase. All these phosphors sintered at 1023 K exhibit two major luminescence lines at 594 and 614 nm under near-UV light of 395 nm excitation, corresponding to Eu³⁺ ions typical transitions of ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂. The optimum concentration of Eu³⁺ ions is 9 mol% for C-LBTO:xEu³⁺ samples and the quenching interaction type is the nearest-neighbor ion interaction. The thermal stability of the C-LBTO:0.09Eu³⁺ sample was investigated in detail and the device application further suggests that C-LBTO:0.09Eu³⁺ can be used as a red phosphor for near-UV excited w-LEDs in lighting.