Structure and luminescence of Ca_2Si_5N_8:Eu^(2+) phosphor for warm white light-emitting diodes  

作　　者：魏小丹 蔡丽艳 鲁法春 陈小龙 陈学元 刘泉林 

机构地区：[1]School of Materials Science & Engineering and State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing [2]Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences [3]Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences

出　　处：《Chinese Physics B》2009年第8期3555-3562,共8页中国物理B（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No 50672007);Program for the New Century Excellent Talents of China (Grant No NCET-06-0082);the National Basic Research Program of China (Grant No2007CB936202)

摘　　要：We have synthesized Ca2Si5N8：Eu^2＋ phosphor through a solid-state reaction and investigated its structural and luminescent properties. Our Rietveld refinement of the crystal structure of Ca1.9Eu0.1Si5N8 reveals that Eu atoms substituting for Ca atoms occupy two crystallographic positions. Between 10 K and 300 K, Ca2Si5N8：Eu^2＋ phosphor shows a broad red emission band centred at -1.97 eV-2.01 eV. The gravity centre of the excitation band is located at 3.0 eV 3.31 eV. The centroid shift of the 5d levels of Eu^2＋ is determined to be -1.17 eV, and the red-shift of the lowest absorption band to be - 0.54 eV due to the crystal field splitting. We have analysed the temperature dependence of PL by using a configuration coordinate model. The Huang-Rhys parameter S = 6.0, the phonon energy hv = 52 meV, and the Stokes shift △S = 0.57 eV are obtained. The emission intensity maximum occurring at -200 K can be explained by a trapping effect. Both photoluminescence （PL） emission intensity and decay time decrease with temperature increasing beyond 200 K due to the non-radiative process.We have synthesized Ca2Si5N8：Eu^2＋ phosphor through a solid-state reaction and investigated its structural and luminescent properties. Our Rietveld refinement of the crystal structure of Ca1.9Eu0.1Si5N8 reveals that Eu atoms substituting for Ca atoms occupy two crystallographic positions. Between 10 K and 300 K, Ca2Si5N8：Eu^2＋ phosphor shows a broad red emission band centred at -1.97 eV-2.01 eV. The gravity centre of the excitation band is located at 3.0 eV 3.31 eV. The centroid shift of the 5d levels of Eu^2＋ is determined to be -1.17 eV, and the red-shift of the lowest absorption band to be - 0.54 eV due to the crystal field splitting. We have analysed the temperature dependence of PL by using a configuration coordinate model. The Huang-Rhys parameter S = 6.0, the phonon energy hv = 52 meV, and the Stokes shift △S = 0.57 eV are obtained. The emission intensity maximum occurring at -200 K can be explained by a trapping effect. Both photoluminescence （PL） emission intensity and decay time decrease with temperature increasing beyond 200 K due to the non-radiative process.

关 键 词：LUMINESCENCE STRUCTURE NITRIDE EUROPIUM white light-emitting diode （LED） 

分 类 号：O482.31[理学—固体物理] TN312.8[理学—物理]