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Synthesis of SiAlON-type Phosphors and Their Photoluminescence Property
|Jeong Ho Ryu , Youn-Gon Park , Chul Soo Yoon|
Samsung Electro Mechanics Co, 314, Meatan 3-Dong, Suwon 443-743, Korea, South
Rare-earth doped oxynitride or nitride phosphors have been found to have longer excitation and emission wavelengths compared to their oxidic counterparts. The luminescence is attributable to the strong nephelauxetic effect and large crystal field splitting as the activator ions are coordinated to nitrogen. Besides this oxynitride or nitride phosphors are expected to have high thermal and chemical stabilities because the crystal structure of the host lattice is built on stiff frameworks consisting of Si-N or Al-N tetrahedron.
We report yellow and green oxyniride phosphors which are suitable for use in white LEDs: Eu2+ activated α/β-SiAlON. α-SiAlON, isostructural with α-Si3N4, has a solid solution composition Mm/vSi12-(m+n)Alm+nOnN16-n. In this structure, m+n(Si-N) bonds are replaced by m(Al-N) bonds and n(Al-O) bonds; the charge discrepancy caused by the substitution is compensated by the introduction of a modifying cation M including Li, Mg, Ca, Y and most lanthanides. The M cations occupy the interstitial sites in the crystal lattice, and are coordinated by seven (O,N) anions at three different M-(O,N) distances. The structure of β-SiAlON is derived from β-Si3N4 by equivalent substitution of Al-O for Si-N, and its chemical composition can be written as Si6-zAlzOzN8-z (z represents the number of Al-O pairs substituting for Si-N pairs and 0<z<4.2). β-SiAlON has a hexagonal crystal structure and the P63 space group.
In this structure there are continuous channels parallel to the c direction. In this work, f ine SiAlON:Eu2+ phosphors were synthesized using a gas pressure sintering (GPS) equipment. The crystallinity, surface morphology and chemical composition were presented. And moreover, temperature dependent photoluminescence (PL) properties of the prepared SiAlON-type phosphors were investigated in a temperature range from 30 to 150 °C.
Presentation: Poster at E-MRS Fall Meeting 2007, Symposium A, by Jeong Ho Ryu
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-14 07:12 Revised: 2009-06-07 00:44