PDF Publication Title:
Text from PDF Page: 079
Rare Earth-Doped Phosphors for White LEDs Chapter 278 43 (Uheda et al., 2006a). Si4+ and Al3+ ions are distributed randomly at the 8b site have fourfold nitrogen coordination, forming MN4 (M1⁄4Si4+ and Al3+) tetrahedra corner sharing each other so that they build a 3D framework. The Ca2+ ions occupy sites located in the channels along the c-axis and have fivefold nitrogen coordination to form square pyramids. The average Ca–N bond distance is 0.2493 nm. The luminescence properties of CaAlSiN3:Ce3+ phosphors were first reported by Li et al. (2008a). The excitation spectrum of CaAlSiN3:Ce3+ cov- ers the wide spectral range from 250 to 550 nm and has a strong optical absorption maximum in the blue region (Fig. 40). The phosphor exhibits a broad, asymmetrical yellow emission band peaking at 570 nm. The emission band is composed of two components with maxima at around 556 and 618 nm, whose profile can be fitted by two typical Gaussian functions. The two bands are ascribed to transitions from the 5d excited state to the doublet ground state (2F7/2 and 2F5/2) of Ce3+, and the energy difference between the two emission bands corresponds to about 1800 cm1, similar to that of the theoretical energy difference between 2F7/2 and 2F5/2 (2000 cm1; Blasse and Grabmaier, 1994). Optimization of the Ce3+ content yields the highest emission intensity for the composition (Ca0.9Ce0.1)AlSiN3, which has an external quantum efficiency of 54% at an excitation wavelength of 450 nm. In addition, CaAlSiN3:Ce3+ shows an excellent thermal stability against tem- perature quenching. At 150°C, the emission intensity of the phosphor is quenched by only 10% with respect to that at 25°C. 1 0.5 ex. em 0 200 300 400 500 600 700 800 Wavelength (nm) Excitation and emission spectra of CaAlSiN3:Ce3+. Redrawn from Li, J., Watanabe, T., Sakamoto, N., Wada, H., Setoyama, T., Yoshimura, M. 2008a. Synthesis of a multinary nitride, Eu-doped CaAlSiN3 from alloy at low temperatures. Chem. Mater. 20, 2095–2105. FIG. 40 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 (Standard Web Page)