PDF Publication Title:
Text from PDF Page: 061
FIG. 17 Sr SiO4 LiO4 0.2642(2) 0.2638(5) 0.2638(2) 0.2571(5) 0.2571(5) c a b Rare Earth-Doped Phosphors for White LEDs Chapter 278 25 Crystal structure and coordination environment of SrO8 dodecahedron in Li2SrSiO4. The unit of bond distance is nm. Pictures were drawn based on the structure data obtained from the database (ICSD #167334). stability. Li2SrSiO4:Eu2+ is also one of the recently reported orthosilicate phos- phors used in white LEDs (He et al., 2010; Kulshreshtha et al., 2009; Levshov et al., 2011; Pardha Saradhi and Varadaraju, 2006; Toda et al., 2006). Li2SrSiO4 has a trigonal (usually expressed by hexagonal setting) structure with space group P3121, a 1⁄4 0.5030 nm, c 1⁄4 1.2470 nm, and V 1⁄4 0.3155 nm3 (Fig. 17), being isostructural with Li2EuSiO4 (Haferkorn and Meyer, 1998). The LiO4 and SiO4 tetrahedra are connected by sharing corners, forming a three- dimensional (3D) network able to accommodate Sr2+ with a distorted eightfold coordination (Fig. 17). The activator Eu2+ ions can substitute the Sr sites. The average Sr–O bond distance is 0.2633 nm. The SrO8 dodecahedron can be represented as a distorted cube in between a regular cube and an antiprism, like in YAG:Ce3+ phosphors. Furthermore, the shape of the SrO8 dodecahedron is a little closer to a regular antiprism than YO8 in YAG:Ce3+. It is expected then that inducing a lower symmetry of the Sr site in SrO8 would result in Li2SrSiO4:Eu2+ displaying longer wavelength emission compared to YAG:Ce3+. Li2SrSiO4:Eu2+ is efficiently excited by near-UV and blue light and shows a reddish–yellow emission with a peak at around 570 nm (Fig. 18). The emis- sion band is located at a longer wavelength than that of YAG:Ce3+ (550 nm), rather similar to that of Sr-rich (Ba,Sr)2SiO4 (575 nm). The emission intensity under excitation at 450 nm is almost the same as that of YAG:Ce3+. Further- more, the phosphor has better thermal stability with respect to temperature quenching compared with Sr-rich (Ba,Sr)2SiO4. As shown in Fig. 19, the decrease in the emission intensity of the phosphor is only a 10% and 20% at 100 and 150°C, respectively, indicating less thermal quenching. 0.2642(2) 0.2638(5) 0.2671(2)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)