Effects of Flux Additives on Characteristics of Y 2.95 Al ₅ O ₁₂ :0.05Ce ³⁺ Phosphor: Thermal Stability and Application to WLEDs

Y2.95Al5O12:0.05Ce3+phosphors were synthesized via the solid-state reaction method using fluxes of H3BO3and BaF2. The thermal stability and luminescence of Y2.95Al5O 12:0.05Ce3+prepared with 6 wt% BaF2flux additive (Sample II) were compared with those of Y2.95Al5O12:0.05Ce3+prepared with 7 wt% H3BO3flux additive (Sample I). The crystallinity of Sample I was found to be better than that of Sample II. This difference in crystallinity, which led to a difference in thermal stability, is well explained by the presence of defects. Moreover, Sample I, Sample II, and commercial Y3Al5O2:Ce3+phosphors were coated onto 450-nm chips for the fabrication of white light-emitting diodes (WLEDs). The luminous efficacy (@350 mA) of Sample-I-based (68.98 lm/W) and commercial-Y3Al5O12:Ce3+-based (70.87 lm/W) WLEDs was lower than that (77.2 lm/W) of the Sample-II-based WLED due to the powder morphology of the phosphors.