Synthesis and photoluminescent properties of europium-activated M2SnO4 (M=Ca, Sr, Zn) phosphors

• Main Authors: Yu-Chung Chen, 陳俞仲
• Other Authors: Yen-Hwei Chang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/02072964037271049259

博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 94 === 　　The synthesis and photoluminescent (PL)properties of calcium, strontium and zinc stannate crystals doped with europium grown by mechanically activated in a high energy vibro-mill and sol-gel method have been investigated. 　　The characteristics of Ca2SnO4: Eu3+ phosphors were found to depend on the amounts of europium ions. The calcined powders emit bright red luminescence centered at 618nm due to 5D0→7F2 electric dipole transition. Both XRD data and the emission ratio of (5D0→7F2)/( 5D0→7F1) reveal that the site symmetry of Eu3+ ions decreases with increasing doping concentration. The maximum PL intensity has been obtained for 7 mol% concentration of Eu3+ in Ca2SnO4. 　　The characteristics of Sr2SnO4:Eu3+ powders were found to depend on the heating conditions and the amounts of europium ions. In the SEM morphology observations, the shape of grains was changed gradually from granular to circularity-like as the calcination temperature increasing from 1000℃ to 1300℃. The calcined powders emit bright red luminescence centered at 619nm due to the electric dipole transition of 5D0→7F2, and the powders fired at 1200℃ were found to have the maximum PL intensity. The maximum PL intensity was obtained for 5 mol% concentration of Eu3+ in Sr2SnO4. 　　Single phase Sr2SnO4 crystal was formed after heating Sr2SnO4 precusor at 800℃ for 10h by solgel method. The change of crystallinity and grain size will affect the luminescent properties. 　　One broaden emission band from the Zn2SnO4: Eu2+ phosphor calcined at 1000℃ to 1200℃ for 3h in air is clearly observed at 525nm under 374nm UV ray excitation. The emission band from Zn2SnO4: Eu3+ can also be observed under 464nm-ray excitation. The reduction of Eu3+→Eu2+ was firstly discovered in stannate phosphor of Zn2SnO4: Eu synthesized in air condition. Post annealing in 11% (H2/H2+N2) atmosphere reduced the Eu3+ ions and changed the emission spectra. The CIE chromaticity is (0.26, 0.49), shows green light. Codoping Nd ions will enhance the emission intensity and the maximum is 2% Nd concentration. Codoping Nd ions also induced fluorescence.