The discovery of new luminescent materials for use in light-emitting diodes(LEDs) has been of great interest, since LED-based solid state lighting applications are attracting a lot of attention in the energy saving and environmental fields. Recent research trends have centered on the discovery of new luminescent materials rather than on fine changes in well-known luminescent materials. In a sense, the novelty of our study beyond simple modification or improvement of existing phosphors. A good strategy for the discovery of new fluorescent materials is to introduce activators that are appropriate for conventional inorganic compounds, that have well-defined structures in the crystal structure database, but have not been considered as phosphor hosts. Another strategy is to discover new host compounds with structures that cannot be found in any existing databases. We have pursued these two strategies at the same time using composite search technology with particle swarm optimization(PSO). In this study, using PSO, we have tracked down a search space composed of Sr-Al-Si-O-N and have discovered a new phosphor structure with yellow luminescence; this material is a potential candidate for UV-LED applications

ZnS:Mn, Dy yellow phosphors for White Light Emitting Diode were synthesized by a solid state reaction methodusing ZnS, MnSO4·5H2O, S and DyCl3·6H2O powders as starting materials. The mixed powder was sintered at 1000oC for 4h in an air atmosphere. The photoluminescence of the ZnS:Mn, Dy phosphors showed spectra extending from 480 to 700nm,peaking at 580nm. The photoluminescence of 580nm in the ZnS:Mn, Dy phosphors was associated with 4T1→6A1 transitionof Mn2+ ions. The highest photoluminescence intensity of the ZnS:Mn, Dy phosphors under 450nm excitation was observedat 4mol% Dy doping. The enhanced photoluminescence intensity of the ZnS:Mn, Dy phosphors was explained by energytransfer from Dy3+ to Mn2+. The CIE coordinate of the 4 mol% Dy doped ZnS:Mn, Dy was X=0.5221, Y=0.4763. Theoptimum mixing conditions for White Light Emitting Diode was obtained at the ratio of epoxy:yellow phosphor=1:2 formCIE coordinate.