Rietveld refinement and optical properties of SrWO_4:Eu^(3+) powders prepared by the non-hydrolytic sol-gel method  

作　　者：P.F.S.Pereira I.C.Nogueira E.Longo E.J.Nassar I.L.V.Rosa L.S.Cavalcante 

机构地区：[1]Chemistry Institute, University of the State of Sao Paulo Julio de Mesquita Filho-UNESP, Francisco Degni,Araraquara-SP 14800-900, Brazil [2]LIEC-Chemistry Department, Federal University of Sao Carlos, Via Washington Luis Km 235,Sao Carlos-SP 13565-905, Brazil [3]University of Franca-UNIFRAN,Via Dr.Armando Sales de Oliveira,No.201, Franca-SP 14404-600, Brazil [4]CCN-DQ-GERATEC, University of the State of Piauí, Joao Cabral, 2231, P.O.Box 391,Terezina, PI 64002-150, Brazil

出　　处：《Journal of Rare Earths》2015年第2期113-128,共16页稀土学报（英文版）

基　　金：Project supported by Brazilian Research Financing Institutions:Conselho Nacional para o Desenvolvimento de Pesquisa(CNPq) (142760/2008-0;479644-2012-8; Postdoctoral 160922/2012-7);Fundacao para o Amparo a Pesquisa do Estado de S?o Paulo (FAPESP), and Conselho de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)

摘　　要：We investigated the effect of annealing time on the structure and optical properties of Sr WO4：Eu^3＋ powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 ℃ for 2,4,8 and 16 h.Thermogravimetric and differential thermal analyses revealed that Sr WO4：Eu^3＋ powders were obtained at about 800 ℃.X-ray diffraction patterns and Rietveld refinement data confirmed that all powders had a scheelite-type tetragonal structure.Micro-Raman and Fourier transform infrared spectra indicated structural order at short range and anti-symmetric stretching vibrations of O-W-O bonds associated with tetrahedral[WO4]clusters.Optical properties were investigated by ultraviolet-visible（UV-vis）diffuse reflectance,and photoluminescence（PL）data which provided the evolution of quantum efficiency（η）and lifetime（τ）.UV-vis spectroscopy evidenced intermediate energy levels within the band gap of Sr WO4：Eu^3＋ powders.PL properties validated that the Eu^3＋ electric-dipole（^5D0→^7F2）transition in PL emission spectra was dominant which proved that Eu^3＋ ions were positioned in a site without an inversion center.[（^5D0→^7F2）/（^5D0→^7F1）]band ratios showed that Eu^3＋ ions were located in a low symmetry environment.The PL emission,ηandτproved the dependence on the annealing time in the behavior of Sr WO4：Eu3＋powders with a higher relative emission PL intensity as well as higherηandτvalues related to other samples when heat treated at 800℃ for 8 h.We investigated the effect of annealing time on the structure and optical properties of Sr WO4：Eu^3＋ powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 ℃ for 2,4,8 and 16 h.Thermogravimetric and differential thermal analyses revealed that Sr WO4：Eu^3＋ powders were obtained at about 800 ℃.X-ray diffraction patterns and Rietveld refinement data confirmed that all powders had a scheelite-type tetragonal structure.Micro-Raman and Fourier transform infrared spectra indicated structural order at short range and anti-symmetric stretching vibrations of O-W-O bonds associated with tetrahedral[WO4]clusters.Optical properties were investigated by ultraviolet-visible（UV-vis）diffuse reflectance,and photoluminescence（PL）data which provided the evolution of quantum efficiency（η）and lifetime（τ）.UV-vis spectroscopy evidenced intermediate energy levels within the band gap of Sr WO4：Eu^3＋ powders.PL properties validated that the Eu^3＋ electric-dipole（^5D0→^7F2）transition in PL emission spectra was dominant which proved that Eu^3＋ ions were positioned in a site without an inversion center.[（^5D0→^7F2）/（^5D0→^7F1）]band ratios showed that Eu^3＋ ions were located in a low symmetry environment.The PL emission,ηandτproved the dependence on the annealing time in the behavior of Sr WO4：Eu3＋powders with a higher relative emission PL intensity as well as higherηandτvalues related to other samples when heat treated at 800℃ for 8 h.

关 键 词：SrWO4 Rietveld refinement optical band gap Eu^(3+) ＋-rare earth LUMINESCENCE 

分 类 号：TQ132.33[化学工程—无机化工]