PDF Publication Title:
Text from PDF Page: 110
74 Handbook on the Physics and Chemistry of Rare Earths 1 0.5 0 300 ex. em 400 500 600 700 Wavelength (nm) Excitation and emission spectra of (Sr,Ba)3AlO4F:Ce3+ at room temperature. Redrawn from Im, W.B., Brinkley, S., Hu, J., Mikhailovsky, A., Den Baars, S.P., Sechadri, R., 2010. Sr2.975xBaxCe0.025AlO4F: a highly efficient green-emitting oxyfluoride phosphor for solid state white lighting. Chem. Mater. 22, 2842–2849. 4.5 Energy Transfer Type Phosphors Energy transfer among the multiple emitting ions in a phosphor is a mean of controlling the emission color. Some pairs of rare earth ions lead to efficient energy transfer, for example, Ce3+ ! Tb3+ (green emission) and Eu2+/Ce3+!Mn2+ (green or red emission). The emission of Tb3+ occurs in the green region with sharp lines due to 4f–4f transitions. On the other hand, since the 3d orbitals of Mn2+ are themselves outer orbitals, the emission color is strongly dependent on the crystal field of the host crystal. In general, the colors emitted from Mn2+ with tetrahedral coordination are greenish and those from Mn2+ octahedral coordination are reddish, respectively. Absorption in the visible region by Tb3+ and Mn2+ is very low due to the forbidden character of 4f–4f and 3d–3d transitions. Therefore, the energy transfer is quite a useful method to improve the absorption of Tb3+ and Mn2+. 4.5.1 Y2Si3O3N4:Ce3+,Tb3+ Phosphors Y2Si3O3N4:Ce3+,Tb3+ is one of the color-tunable phosphors for white LEDs based on energy transfer from Ce3+ to Tb3+ (Zhu et al., 2015). Fig. 73 shows the excitation and emission spectra of the material with composition (Y1xyCexTby)2Si3O3N4 (x1⁄40, 0.02 and y1⁄40, 0.04). Y2Si3O3N4:Ce3+ exhi- bits a blue emission with peaking at 480 nm under near-UV excitation (Fig. 73B), while Y2Si3O3N4:Tb3+ exhibits a multipeak excitation band from 250 to 450 nm (Fig. 73A). The energy transfer from Ce3+ to Tb3+ is known to occur through two different mechanisms: (i) energy transfer from a 5d state of Ce3+ to the 5D3 level of Tb3+ due to their similar energy (Resonant energy FIG. 72 Normalized intensity (a.u.)PDF Image | HANDBOOK ON THE PHYSICS AND CHEMISTRY OF RARE EARTHS
PDF Search Title:
HANDBOOK ON THE PHYSICS AND CHEMISTRY OF RARE EARTHSOriginal File Name Searched:
Chemistry-Rare-Earths-49.pdfDIY PDF Search: Google It | Yahoo | Bing
Sulfur Deposition on Carbon Nanofibers using Supercritical CO2 Sulfur Deposition on Carbon Nanofibers using Supercritical CO2. Gamma sulfur also known as mother of pearl sulfur and nacreous sulfur... More Info
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |