Jeong Ho Ryu

Luminescent Properties of Ca-α-SiAlON : Eu2 + Phosphors Synthesized by Gas-Pressured Sintering

Rare-earth-doped oxynitride or nitride compounds have been reported to be photoluminescent and may then serve as new phosphors with good thermal and chemical stabilities. In this work, Ca-α-SiAlON:Eu 2+ based yellow and orange oxynitride phosphors with compositions of Ca 0.485 Eu 0.015 Si 9.2 Al 2.8 O 1.8 N 14.2 and Ca 0.94 Eu 0.06 Si 9 Al 3 ON 15 were prepared using the gas-pressured sintering method. The crystallinity and particle morphology of the prepared phosphors were characterized. The temperature dependence of photoluminescence properties was investigated from 25 to 150°C. The Stokes shift and zero-phonon line was calculated mathematically and estimated from the spectral data. The prepared Ca-α-SiAlON:Eu 2+ phosphors showed superior thermal quenching properties compared to commercially used YAG:Ce 3+ phosphors. In addition, the activation energies (ΔE) for thermal quenching of the prepared Ca-α-SiAlON:Eu 2+ phosphors were determined by Arrhenius fitting.

Simple Route for Y3Al5O12 : Ce3 + Colloidal Nanocrystal via Laser Ablation in Deionized Water and its Luminescence

Pulsed laser ablation in deionized water was successfully employed to synthesize a Y 3 Al 5 O 12 :Ce 3+ nanocolloidal suspension. The obtained suspension consisted of a well-dispersed YAG:Ce 3+ nanocrystal with a spherical shape and a size ranging from 5 to 25 nm. Blueshift phenomena were found in excitation and emission spectra, which have not been explained by previous crystal-field splitting theory. This Letter focuses on the simple synthetic route of colloidal YAG:Ce 3+ nanocrystals via laser ablation in the liquid phase and 5d energy level of Ce 3+ . A phenomenological model based on the concept of crystal-field theory modified by the covalency contribution is introduced to explain the blueshift phenomena in luminescence.