Preparation of phosphors AEu(MoO4)2 (A = Li, Na, K and Ag) by sol-gel method

• Published in: Applied physics. A, Materials science & processing Vol. 94; no. 2; pp. 365 - 371
• Main Authors: Guo, Chongfeng, Wang, Shuiting, Chen, Tao, Luan, Lin, Xu, Yan
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.02.2009; Springer
• Subjects: Band spectra; Characterization and Evaluation of Materials; Charge transfer; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Excitation; Field emission; Machines; Manufacturing; Materials science; Materials synthesis; materials processing; Nanotechnology; Optical and Electronic Materials; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other solid inorganic materials; Phase transformations; Phosphors; Photoluminescence; Physics; Physics and Astronomy; Processes; Silver; Sol gel process; Surfaces and Interfaces; Thin Films; 78.55.-m; 71.20.Ps; Scanning electron microscopy; Scheelite structure; Tetragonal lattices; Crystallization; Photoluminescence; Thermogravimetry; Differential thermal analysis; XRD; Molybdates; Field emission electron microscopy; Energy-level transitions; Phosphors; Excitation spectrum; Charge transfer; Sol-gel process
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-008-4811-9

A series of double molybdates phosphors AEu(MoO 4 ) 2 (A = Li, Na, K and Ag) have been prepared by sol-gel method. Their crystal structure and luminescent properties have also been investigated in a comparable way. The crystallization processes of the phosphor precursors were characterized by X-ray diffraction (XRD) and thermogravimetry-differential thermal analysis (TG-DTA). Field emission scanning electron microscopy (FE-SEM) was also used to characterize the shape and size distribution of the phosphors. Samples except KEu(MoO 4 ) 2 showed tetragonal scheelite structure in the range of our experiments, and no phase transition appeared. Phosphor KEu(MoO 4 ) 2 possessed two structures, and the phase transition took place at about 800°C. All samples with high purity could be obtained at about 500°C for 5 hours, and they all showed intense red light peaked at 616 nm originated from 5 D 0 → 7 F 2 emission of Eu 3+ under the excitation of 465 nm or 394 nm light. The excitation spectra of phosphors AEu(MoO 4 ) 2 (A = Li, Na, and K) are composed of a strong broad charge transfer (CT) band and some sharp lines, and the relative intensity of CT band, the two strongest absorption lines at 395 nm and 465 nm are comparative, so these three phosphors are good red phosphor candidates for violet or blue LEDs. For the excitation spectrum of phosphor AgEu(MoO 4 ) 2 , intensities of CT band and the absorption line at 395 nm are much weaker than that of line at 465 nm, thus phosphor AgEu(MoO 4 ) 2 is only suit for GaN-based blue LED.