136 resultados para BAFBR-EU2
Resumo:
The local structure and the valences of europium in SrBPO5:Eu prepared in air were checked by means of XAFS at Eu-L-3 edge. From the EXAFS results, it was discovered that the doped europium atoms were nine-coordinated by oxygen atoms and the distances of bond Eu-O were 2.42 Angstrom in the host. From the XANES data, it was found that the divalent and trivalent europium coexisted in the matrix. The emission spectra excited by VUV or UV exhibited a prominent broad band due to the 4f(6)5d-4f(7) transition of Eu2+ ions, which indicated that the trivalent europium ions were reduced in air in the matrix at high temperature by the defects [V-Sr]" formed by aliovalent substitution between Sr2+ and Eu3+ ions. The VUV excitation spectra in 100-200 nm range showed that the matrix had absorption bands with the maxima at about 130 and 150 nm, respectively.
Resumo:
XAFS (EXAFS and XANES) at Eu-L-3 edge were used to determine the local structure and the valences of europium in CaBPO5:Eu prepared in air. The results of EXAFS showed that the doped europium atoms were nine-coordinated by oxygen atoms and the distances of bond Eu-O were 2.39 Angstrom in the host lattice. XANES at Eu-L-3 edge exhibited that Eu2+ and Eu3+ coexisted in the matrix. The luminescent spectrum of the material excited by VUV at 147 nm presented a similar spectrum with that excited by f-f transition of Eu2+ at 396 nm and f-d transition of Eu2+ at 312 nm. The broad emission band due to both 4f(6)5d - 4f(7) transition of EU2+ and f - f transition of Eu3+ could be observed in emission spectra, which indicated that the trivalent europium ions were reduced in air in the matrix at high temperature by the defects [V-Cn]" formed by aliovalent substitution between Ca2+ and Eu3+ ions. The UV excitation spectrum showed the typical f-f transition of Eu3+ and f-d transition of Eu2+. The bands with the maxima at about 113 and 158 nm in VUV excitation spectrum were assigned to originate from the absorption of the host lattice.
Resumo:
Using the Bridgeman-Stockbarger method, the KMgF3:EU2+ single crystal was grown. The color centers in unirradiated KMgF3:Eu crystal were studied. By thermal annealing, we confirmed the 422-nm emission resulted from color centers and oxygen centers, and we proved the energy transfer from EU2+ to color centers. From spectra, the relative oxygen content in crystal was calculated, and the relationships of oxygen displacing fluorine were studied.
Resumo:
Ba Li F3 Gd3+ Eu2 + Gd3+ Eu2 + , .Gd3+ ( ) 0 .3 % , , PSA=1 .3 5 1 0 5s- 1 . Gd3+ 0 .3 % , Gd3+ Eu2 + Gd3+ , Gd3+ , ,Eu2 + ,
Resumo:
:Eu2 + ,Dy3 + , , , 5 16nm ,Eu2 + 5d 8S7/ 2 12 0 0 0lx 2 0 , 10 , 3 5 3cd/m2 , :x =0 2 84 2 ,y =0 5 772 ; 5 5 5 , 0 0 1cd/m2 ; 30 , ,
Resumo:
Eu2 +Ba2 LiB5 O10 ,Ba2 MgB2 O6 ,Ba2 Be2 B2 O6 ,BaLiBO3,SrB4 O7SrAl2 B2 O7 . , ,.
Resumo:
, P O[1 ] , , , , [2 ] [3] [4 ] X [5] , [6 ] , , , , , X , ,La4 - x(P2 O5) 3:Eux : 1 0 .0 0 0 0 g La2 O3(99.99% ) 2 .0 0 0 0 g Eu2 O3(99.99% ) , HNO3( ) , 0 .1 mol/ L La(N...
Resumo:
KMgF3 Eu ,Bridgman StockbargerKMgF3 Eu : ,Eu2 + ff , 4 2 0nm ; ,Eu2 + 36 0nm ,Eu2 +
Resumo:
The polycrystals of KZnF3 : Eu have been synthesized by hydrothermal method at 220 degreesC, The product was characterized by XRD, XPS and SEM. The emission and excitation spectra of europium ion were measured. The existence of Eu2+ ion was confirmed by ESR and spectroscopy. The sites were possibly occupied by Eu2+ ions, charge compensation in this crystal were also discussed.
Resumo:
The luminescence properties of CaBPO5: Eu, Tb phosphor and the sensitization of Ce3+ were investigated. The CaBPO5: Eu, Tb phosphors were synthesized in the ambient air and the emission spectra of Eu3+, Tb3+ and Eu2+ were Observed in the phosphor. The result shows that there is electron transfer between conjugate rare earth ions. Sensitization of Ce3+ can improve the intensity of emission of Tb3+ and Eu2+. A novel trichromatic lamp phosphor codoped with Eu3+-Tb3+ in matrix CaBPO5 is then predicted.
Resumo:
CaY1-xBO4: xEu was synthesied by solid state reaction method, and the displacement and luminescence of the Eu3+ in CaYBO4 host were studied. Two luminescent centers could be observed at certain Eu3+-concentration, indicating that the Eu3+ occupies two different crystallographic sites. This result shows that the Eu3+ occupies two different Y3+ sites in CaYBO4. The investigation on Eu-O charge transfer bands indicates that the larger distortion or the lower symmetry of Eu3+ site is,the shorter wavelength of the Eu-O charge transfer band is. When the Eu3+-concentration is high (x > 0.10), Eu3+ occupies the sites of Ca2+ and is reduced to Eu2+.
Resumo:
The luminescent materials SrB4O7:Eu and BaB8O13:Eu were synthesized, and the valence states of europium in the materials were measured by means of XANES at Eu-L-3 edge. It is found that the Ed(3+) and Eu2+ ions are all present in the materials, and more Eu3+ ions can be reduced in SrB4O7:Eu than in BaB8O13:Eu. The excitation and emission spectra of Eu3+ in SrB4O7:Eu and BaB8O13:Eu were determined.
Resumo:
The spectroscopic feature of divalent Sm2+, Eu2+, Tm2+ and Yb2+ is discussed in this paper. Especially the spectroscopic properties of some berates containing tetrahedral BO4 group such as SrB4O7, SrB6O10 and BaB8O13 doped with these divalent ions are reported. When the divalent alkaline earth ion in these berates is replaced partially by the above trivalent rare earth ion, the charge carried in the produced defects can be used as reductant to reduce the doped rare earth ion into divalent state at high temperature even in air. Therefore, a convenient and safe method is provided to prepared phosphors doped with these divalent rare earths.
Resumo:
KZn F3 KZn F3 Eu, SEM ;XPS , ; ESR ,KZn F3 Eu Eu2 + Eu3 + ,
Resumo:
BaMAl10O17 ,M , ,()M Al2O3 ,Eu2 + ,M=Zn,Cd,Mn,Co,Li Al2O3 ,M=Ca,Be ,Ca ,Be ;Eu2 +M=Li,Be,Zn ,450nm ,50nm , ,Eu2 +M=MnEu2 +Mn2 + ,M=Cd ,Eu2 +
