PDF Publication Title:
Text from PDF Page: 055
Rare Earth-Doped Phosphors for White LEDs Chapter 100 278 19 80 60 40 20 0 50 100 150 200 Temperature (°C) 250 300 FIG. 10 Temperature dependence of the emission intensity of YAG:Ce3+. Redrawn from Chen, L., Lin, C.C., Yeh, C.W., Liu, R.S., 2010. Light converting inorganic phosphors for white light-emitting diodes. Materials 3, 2172–2195. on light output and CRI of white LEDs. According to a configuration- coordinate model, a nonradiative transition from an excited level to a ground level increases with increasing temperature; consequently, the emission inten- sity of phosphors generally decreases with increasing temperature. Fig. 10 shows the temperature dependence of the emission intensity, normalized with respect to the value at 25°C, of a YAG:Ce3+ phosphor. Between 25 and 150°C, the emission intensity decreases by about 13% and the emission band red shifts from 550 to 560 nm. On the other hand, the emission intensities at each temperature obtained upon cooling or heating are the same, indicating that there is little thermal degradation in YAG:Ce3+. Furthermore, the emis- sion intensity of a commercial YAG:Ce3+ phosphor measured at 150°C remains !95% of that measured at room temperature. 4.1.1.2 Sr-Rich (Ba,Sr)2SiO4 Phosphors Sr-rich (Ba,Sr)2SiO4:Eu2+ (BOS or BOSE), in which the Ba:Sr ratio is about 2:8, is one of the promising yellow emission phosphors used in blue-LED-based white LEDs. The crystal structure of alkaline-earth orthosilicate, AE2SiO4 (AE1⁄4Ba, Sr, and Ca), was determined more than 30 years ago by Fields et al. (1972), Catti et al. (1983), and Barbier and Hyde (1985). AE2SiO4 (AE1⁄4Ba and Sr) have two morphologies: monoclinic (b-type) phase, which crystallizes at temperatures below 85°C; and orthorhombic (a0-type) phase, which crystallizes at temperatures above 85°C. Both b-type and a0-type phases have two kinds of cation sites which have fairly different crystallo- graphic environments; M(I) and M(II) sites have 10-fold and ninefold oxygen coordination, respectively. AE2SiO4:Eu2+ (AE 1⁄4 Ba and Sr) phosphors have Relative intensity (%)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 (Standard Web Page)