Narrow Results

A series of oxonitridosilicates phosphors Ba-Si_x-O-N /Eu²⁺ (x=Si/Ba=1~8, 5atom% Eu²⁺) were synthesized using traditional solid-state reaction. For x = 2~8, the main phase of the obtained samples was Ba₃Si₆O₁₂N₂. All Ba-Si_x-O-N /Eu²⁺(x = 1~8) materials could be efficiently excited in the UV to visible region(310~450nm) and had a green emission at 508~522nm, making them attractive as conversion phosphors for white LED applications. With increasing x values, the emission peaks shifted to the longer wavelength region, while the emission intensity had a maximum at x = 6. The influence of the firing times was also discussed, after twice fired, there was a tendency of single-phased formed of the obtained materials and the emission intensity was greatly improved.

In this paper, CaO-B₂O₃-2SiO₂: Eu${}^{2+}$ and CaO-B₂O₃-2SiO₂: Eu${}^{2+}$, Ce${}^{3+}$ fluorescent glasses have been synthesized by a conventional melt-quenching method. First, under 350nm excitation, the CaO-B₂O₃-2SiO₂: Ce${}^{3+}$ luminescent glass emits light at about 400nm, and the optimum dosage is 0.3mol%. Then, under 400nm UV excitation, the CaO-B₂O₃-2SiO₂: Eu${}^{2+}$ luminescent glasses showed a strong emission with a peak around 460nm and a half wavelength of 95nm. The results showed that the luminescence of this glass was greatest when the doping amount was 0.3mol% and gradually decreased with increase of the doping amount. After calculation and analysis, it was found that this was due to the nonradiative energy transfer between Eu${}^{2+}$ ions. The mechanism of energy transfer was dipole–dipole interaction. Finally, Ce${}^{3+}$/Eu${}^{2+}$ co-doped luminescent glasses were also successfully prepared with strong emission. The existence of energy transfer was demonstrated by theoretical and practical measurement data. CaO-B₂O₃-2SiO₂: Ce${}^{3+}$, Eu${}^{2+}$ can be used as blue fluorescent glass for white light illumination.

Photoluminescence (PL) spectra, light flux, color temperatures and color coordinates of white light emitting diodes that are based on CaGa₂S₄:Eu${}^{2+}$–CaS:Eu${}^{2+}$ composite solution and industrial phosphor were analyzed. The study was carried out continuously for a 1000 h with two white LEDs which based on an exciting InGaN wavelength of 450 nm with a power of 10 W. Luminous flux and color temperatures were investigated during 200, 400, 600, 800 and 1000 h. All experiments were carried out for both CaGa₂S₄:Eu${}^{2+}$–CaS:Eu${}^{2+}$ and industrial phosphor and comparatively analyzed. Consequently, the application perspectives of CaGa₂S₄:Eu${}^{2+}$–CaS:Eu${}^{2+}$ composite solution in the white LEDs technologies are presented.