106 resultados para Sm3
Resumo:
New glasses of 16.66SrO16.66[(1 x)Bi2O3xSm2O3]16.66Nb2O550Li2B4O7 (0 x 0.5, in molar ratio), i.e., the pseudo-binary Sm2O3-doped SrBi2Nb2O9Li2B4O7 glass system, giving the crystallization of Sm3+-doped SrBi2Nb2O9 nanocrystals are developed. It is found that the thermal stability of the glasses against the crystallization and the optical band gap energy increases with increasing Sm2O3 content. The formation of fluorite-type Sm3+-doped SrBi2Nb2O9 nanocrystals (diameters: 1337 nm) with a cubic structure is confirmed in the crystallized (530 C, 3 h) samples from X-ray powder diffraction analyses, Raman scattering spectrum measurements, and transmission electron microscope observations. The effect of Sm3+-doping on the microstructure, Raman scattering peak positions, and dielectric properties of composites comprising of fluorite-type SrBi2Nb2O9 nanocrystals and the Li2B4O7 glassy phase is clarified. It is found that fluorite-type SrBi2Nb2O9 nanocrystals transform to stable perovskite-type SrBi2Nb2O9 crystals with an orthorhombic structure by heat treatments at around 630 C.
Resumo:
We present here magnetization, specific heat, and Raman studies on single-crystalline specimens of the first pyrochlore member Sm2Ti2O7 of the rare-earth titanate series. Its analogous compound Sm2Zr2O7 in the rare-earth zirconate series is also investigated in the polycrystalline form. The Sm spins in Sm2Ti2O7 remain unordered down to at least T=0.5 K. The absence of magnetic ordering is attributed to very small values of exchange (cw0.26 K) and dipolar interaction (eff0.15 B) between the Sm3+ spins in this pyrochlore. In contrast, the pyrochlore Sm2Zr2O7 is characterized by a relatively large value of Sm-Sm spin exchange (cw10 K); however, long-range ordering of the Sm3+ spins is not established at least down to T=0.67 K due to frustration of the Sm3+ spins on the pyrochlore lattice. The ground state of Sm3+ ions in both pyrochlores is a well-isolated Kramers doublet. The higher-lying crystal field excitations are observed in the low-frequency region of the Raman spectra of the two compounds recorded at T=10 K. At higher temperatures, the magnetic susceptibility of Sm2Ti2O7 shows a broad maximum at T=140 K, while that of Sm2Zr2O7 changes monotonically. Whereas Sm2Ti2O7 is a promising candidate for investigating spin fluctuations on a frustrated lattice, as indicated by our data, the properties of Sm2Zr2O7 seem to conform to a conventional scenario where geometrical frustration of the spin excludes their long-range ordering.
Resumo:
Chemically modified microporous materials can be prepared as robust catalysts suitable for application in vapor phase processes such as Friedel-Crafts alkylation. In the present paper we have investigated the use of rare earth metal (Ce3+, La3+, RE3+, and Sm3+) exchanged Na-Y zeolites as catalysts for the alkylation of benzene with long chain linear 1-olefin; 1-dodecene. Thermodesorption studies of 2,6-dimethylpyridine adsorbed catalysts (in the temperature range 573 to 873 K) show that the rare earth zeolites are highly Bronsted acidic in nature. A perfect correlation between catalyst selectivity towards the desired product (2-phenyldodecane) and Bronsted acid sites amount has been observed. (c) 2006 Springer Science + Business Media, Inc.
Resumo:
A wet chemical route is developed for the preparation of Sr2CeO4 denoted the carbonate-gel composite technique. This involves the coprecipitation of strontium as fine particles of carbonates within hydrated gels of ceria (CeO2.xH(2)O, 40<x<75) by the addition of ammonium carbonate. During calcination, CeO2.xH(2)O dehydroxylation is followed by the reaction with SrCO3 to form Sr2CeO4 with complete phase purity. Doping of other rare-earths is carried out at the co-precipitation stage. The photoluminescence (PL) observed for Sr2CeO4 originates from the Ce4+-O2- charge-transfer (CT) transition resulting from the interaction of Ce4+ ion with the neighboring oxide ions. The effect of next-nearest-neighbor (NNN) environment on the Ce4+-O2- CT emission is studied by doping with Eu3+, Sm3+ or Yb3+ which in turn, have unique charge-transfer associated energy levels in the excited states in oxides. Efficient energy transfer occurs from Ce4+-O2- CT state to trivalent lanthanide ions (Ln(3+)) if the latter has CT excited states, leading to sensitizer-activator relation, through non-resonance process involving exchange interaction. Yb3+-substituted Sr2CeO4 does not show any line emission because the energy of Yb3+-O2- CT level is higher than that of the Ce4+-O2- CT level. Sr2-xEuxCeO4+x/2 shows white emission at xless than or equal to0.02 because of the dominant intensities of D-5(2)-F-7(0-3) transitions in blue-green region whereas the intensities of D-5(0)-F-7(0-3) transitions in orange-red regions dominate at concentrations xgreater than or equal to0.03 and give red emission. The appearance of all the emissions from D-5(2), D-5(1) and D-5(0) excited states to the F-7(0-3) ground multiplets of Eu3+ is explained on the basis of the shift from the hypersensitive electric-dipole to magnetic-dipole related transitions with the variation in site symmetry with increasing concentration of Eu3+. White emission of Sr2-x SmxCeO4+x/2 at xless than or equal to0.02 is due the co-existence of Ce4+-O2- CT emission and (4)G(4)(5/2)-H-6(J) Sm3+ transitions whereas only the Sm3+ red emission prevails for xgreater than or equal to0.03. The above unique changes in PL emission features are explained in terms of the changes in NNN environments of Ce4+. Quenching of Ce4+-O2- CT emission by other Ln(3+) is due to the ground state crossover arising out of the NNN interactions.
Structural refinement, optical and electrical properties of Ba1-x Sm-2x/3](Zr0.05Ti0.95)O-3 ceramics
Resumo:
Samarium doped barium zirconate titanate ceramics with general formula Ba1-x Sm-2x/3](Zr0.05Ti0.95)O-3 x = 0, 0.01, 0.02, and 0.03] were prepared by high energy ball milling method. X-ray diffraction patterns and micro-Raman spectroscopy confirmed that these ceramics have a single phase with a tetragonal structure. Rietveld refinement data were employed to model BaO12], SmO12], ZrO6], and TiO6] clusters in the lattice. Scanning electron microscopy shows a reduction in average grain size with the increase of Sm3+ ions into lattice. Temperature-dependent dielectric studies indicate a ferroelectric phase transition and the transition temperature decreases with an increase in Sm3+ ion content. The nature of the transition was investigated by the Curie-Weiss law and it is observed that the diffusivity increases with Sm3+ ion content. The ferroelectric hysteresis loop illustrates that the remnant polarization and coercive field increase with an increase in Sm3+ ions content. Optical properties of the ceramics were studied using ultraviolet-visible diffuse reflectance spectroscopy.
Resumo:
Some kinds of rare earth beta-diketone complexes with blue-violet light absorption edge were synthesized using the ligands of thenoyltrifluoroacctone (HTTA), 2, 2'-dipyridyl (BIPY) and different metal ions (Gd3+, Sm3+ and La3+). Their contents, structures and optoelectronic parameters were monitored by elemental analysis, MS, IR and UV spectra. The solubility of rare earth beta-diketone complexes in 2, 2, 3, 3-tetrafluoro-1-propanol (TFP) and absorption properties of their films in the region 300-800 nm were measured. The influence on the difference of absorption maximum from rare earth beta-diketone complexes to beta-diketone ligand by different metal ions was studied. In addition, the thermal stability of rare earth beta-diketone complexes was also reported. (C) 2005 Elsevier B.V. All rights reserved.
Resumo:
Three kinds of rare earth complexes derived from dibenzoylmethane (DBM) ligand were synthesized by reacting free ligand and different rare earth ions(La (3+), Sm3+ and Gd3+). Their contents and structures were postulated based on elemental analysis, LDI-TOF-MS, FT-IR spectra and UV-Vis spectra. Smooth films on K9 glass substrates were prepared using the spin-coating method. Their solubility in organic solvents, absorption and reflection properties of thin film and thermal stability of these complexes were evaluated. These complexes would be a promising recording material for high-density digital versatile disc-recordable (HD-DVD-R) system. (c) 2007 Elsevier B.V. All rights reserved.
Resumo:
,,,:1at.%Nd:YAG236W,62%Sm3+Nd:YAG5Hz,67kW,World-Labo.Co15at.%Yb:YSAG,280fs,62mWQ,,
Resumo:
Sm3+-doped yttrium aluminum perovskite (YAP) single crystal was grown by Czochralski (CZ) method. The absorption and fluorescence spectra along the crystallographic axis b were measured at room temperature. Judd-Ofelt theory was used to calculate the intensity parameters (Omega(t)), the spontaneous emission probability, the branching ratio and the radiative lifetime of the state (4)G(5/2). The peak emission cross-sections were also estimated at 567, 607, and 648 nm wavelengths. (c) 2006 Elsevier B.V. All rights reserved.
Resumo:
The 2 at.% Sm:GdVO4 crystal was grown by the Czochralski method. The segregation coefficient of Sm3+ ion in this crystal is 0.98. The crystal structure of the Sm:GdVO4 crystal was determined by X-ray diffraction analysis. Judd-Ofelt theory was used to calculate the intensity parameters (Omega(i)), the spontaneous emission probability, the luminary branching ratio and the radiative lifetime of the state (4)G(5/2). The stimulated emission cross-sections at 567, 604 and 646 nm are calculated to be 5.92 x 10(-21), 7.62 x 10(-21) and 5.88 x 10(-21) cm(2), respectively. The emission cross-section at 604 nm is 4.4 times lager than that in Sm: YAP at 607 nm. (C) 2007 Elsevier B.V. All rights reserved.
Resumo:
Silica spheres doped with Eu(TTFA)(3) and/or Sm(TTFA)(3) were synthesized by using the modified Stober method. The transmission electron microscope image reveals that the hybrid spheres have smooth surfaces and an average diameter of about 210 nm. Fluorescence spectrometer was used to analyze the fluorescence properties of hybrid spheres. The results show that multiple energy transfer processes are simultaneously achieved in the same samples co-doped with Eu (TTFA)(3) and Sm(TTFA)(3), namely between the ligand and Eu3+ ion, the ligand and Sm3+ ion, and Sm3+ ion and Eu3+, ion. Energy transfer of Sm3+-> Eu3+, in the hybrid spheres leads to fluorescence enhancement of Eu3+ emission by approximately an order of magnitude. The lifetimes of the hybrid spheres were also measured.
Resumo:
hehe,Eu3+Sm3+Yb3+YBO3EuYBO3C2/c Eu3+Eu3+Gd4GdO(BO3)3:EuLi2Lu5O4(BO3)3:EuEu3+Eu3+LuLu1Sr2CeO4O1CeO2Ce
Resumo:
Field Emission Displays, FEDFEDFED (FED)(FED)-(FED) [(LaGaO3: Re3+ (Re = Eu, Tb, Dy, Tm, Sm)][(CaIn2O4: Re3+ (Re = Eu, Pr, Tb, Dy,)][(SrIn2O4: Re3+ (Re = Pr, Tb, Dy)][Lu3Ga5O12:Re3+ (Re = Eu, TbPr)]Pr, Sm, Eu, Tb, Dy, TmSr2CeO4SiO2CaTiO3:Pr3+, Y3Al5O12:Ce3+/Tb3+/Ga2O3:Dy3+XRDFTIRSEMTEM(PL)(CL) (LaGaO3)(Eu3+, Tb3+, Dy3+, Tm3+, Sm3+)(Eu3+, Tb3+, Dy3+, Tm3+, Sm3+)LaGaO3: Eu3+LaGaO3: Dy3+LaGaO3: Tm3+LaGaO3: Sm3+LaGaO3: Sm3+,Tb3+LaGaO3: Tb3+Tb3+LaGaO3: Tb3+LaGaO3: Tm3+FED(Y2SiO5: Ce3+NP-1047)LaGaO3: Sm3+((Zn,Cd)S: AgNP-1020)(LaGaO3: Sm3+,Tb3+), [(LaGaO3: Re3+ (Re = Eu, Tb, Dy, Tm, Sm )] Sr/CaIn2O4Sr/CaIn2O4Pr3+/Tb3+/Dy3+Sr/CaIn2O4Pr3+/ Tb3+/Dy3+Pr3+/Tb3+/Dy3+Sr/CaIn2O4: Pr3+/Tb3+/Dy3+(CL)(PL)CL CaIn2O4:Eu3+CaIn2O4:Eu3+Eu3+ Lu3Ga5O12:Re3+ (Re = Eu, TbPr)UVLu3Ga5O12: Eu3+, Lu3Ga5O12: Pr3+Eu3+, Pr3+Lu3Ga5O12:Tb3+Tb3+ Sr2CeO4UV(Ce4+-O2-) SiO2@CaTiO3:Pr3+SiO2@Y3Al5O12: Ce3+/Tb3+, FESEMTEMSiO2UVSiO2@CaTiO3:Pr3+Pr3+ 1D23H4 (612 nm)SiO2@Y3Al5O12:Ce3+SiO2@Y3Al5O12:Tb3+ Ce3+5d-4fTb3+5D4-7FJ (J = 6, 5, 4, 3)PLCL Ga2O3:Dy3+-Ga2O3:Dy3+--Ga2O3Dy3+--Ga2O3:Dy3+
Resumo:
21DMFCDMFCRDMFCPt/C1PtC1AASPtXRDTEMBETE-TEK2Pt/CRCE-TEK12Pt/CdSm3+Pt3CNTsCNTsPt/CNTs12
Resumo:
-Ca2RSSiO46O2RYGdYVO4LaPO41Eu3+Tb3+Dy3+Sm3+Er3+Pb2SEMAFMCa2R8SiO46O2RYGdEu3+Tb3+Ca2Y8SiO46O26hCs4fC35Do-7F25D4-7F5Eu3+Tb3+Y3+10mol6molCa2Y851O46O2:Eu3Ca2Y8SiO46O2:Tb3+800Pb2Ca2Gd8SiO4 6O2Gd3+Pb2Gd3Gd3nA3YVO4PechiniYvO4:AAEu3 Dy3Sm3Er3YVO4VO43-Dy3Sm3Er3Y3+2molLaPO4Etl3+591nm5Do-7FlTb3543nm5D4-7F5Ce35d-4fTb3Eu3+Tb3+Eu3+Tb3LaPO4:CeTbCe3+Tb3+95XRDx0x1 YVxP1-xO4:Eu3+YVxP1-xO4:Eu3+0x1xEu3+x0Eu3+1Eu3+5Do7F2Etlsx0Y0.98Eu0.l2PO4Eu3+D2d5D07FISD07F2xY0.98Eu0.02VxP1-xO40xl0x0.5Eu3+5 D0-7F2x0.6Eu3+5D0-7F2YVxP1-xO4:A30x1AErSmVO43-A3+VO43-VO43-n-A3+n1VO43-0.1x1xx1VO43-A3+xRVO4:A3+RYLaGdAEuSmErRA3+YVO4GdVO4D2dYVO4GdVO4A3+LaVO4A3+LaVO4C1C1D2dA3+Gd3+A3+GdVO4
