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The dependence of the amount of the BaF2 flux additive on the luminescence of Y2.95Al5O12:0.05Ce3+ phosphors was investigated. The integrated emission intensity of Y2.95Al5O12:0.05Ce3+ prepared without the flux was enhanced by 29% with the addition of BaF2 flux at the optimum amount of 6 wt. %. Such an enhancement can be attributed to the purer phase of Y3Al5O12 and the morphology change from the irregular shape to spherical shape with the smoother surface due to the flux. The morphology and luminescence of Y2.95Al5O12:0.05Ce3+ prepared with the 6 wt. % BaF2 flux additive (Sample II) were further compared with those of Y2.95Al5O12:0.05Ce3+ prepared with the 7 wt. % H3BO3 flux additive (Sample I). The particle size, particle shape, and integrated emission intensity (λex = 450 nm) of the former were found to be larger, more regular, and 6% higher than those of the latter. The difference in the morphology of Samples I and II, which led to the difference in the emission intensity and the external quantum efficiency, were well explained by the particle growth mechanism. [ABSTRACT FROM AUTHOR]

Y2.95Al5O12{:}{\0.05Ce}^3+ phosphors were synthesized via the solid-state reaction method using fluxes of H3BO3 and BaF2. The thermal stability and luminescence of Y2.95Al5O12{:}{\0.05Ce}^3+ prepared with 6 wt% BaF2 flux additive (Sample II) were compared with those of Y2.95Al5O12{:}{\0.05Ce}^3+ prepared with 7 wt% H3BO3 flux 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 Y3Al5O12{:}{\Ce}^3+ 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{:}{\Ce}^3+-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. [ABSTRACT FROM PUBLISHER]

An attempt was made to verify that the inhibition of Sm3+→Eu3+ energy transfer in (Ca0.97Sr0.03)2.82( VO4)2:Sm3+,0.12Eu3+ phosphors at Sm3+ content levels of >0.06 mol can be ascribed to the cross-relaxation effect. The emission peak at around 951 nm attributed to the 6F11/2→6H5/2 transition of Sm3+, which should be barely detectable according to the energy-gap law, was observed in this work by exciting the 4K11/2 state of Sm3 + . The results indicate that cross-relaxation channels, which can depopulate the 4F3/2 state of Sm3+, such as 1st Sm3+ (4F3/2) + 2nd Sm3+ (6H5/2)→1st Sm3+ (6F11/2) + 2nd Sm3+ (6F5/2) and 1st Sm3+ (4F3/2) + 2nd Sm3+ (6H5/2)→1st Sm3+ (6F5/2) + 2nd Sm3+ (6F11/2), may form and become efficient at an Sm3+ doping level of ≧0.06 mol. It was found that the 951-nm emission suffered from concentration quenching, which resulted from a dipole-dipole multipolar interaction. [ABSTRACT FROM AUTHOR]