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1.
Rare earth (RE) pentaborates, both α- and β-polymorphs, are good candidates for photoluminescent hosts suitable for various RE activators. Ce3+ acts not only as an activator itself, but also as a sensitizer to other rare earth activators, like in the case of commercial green phosphor CeMgAl11O19:Tb3+. In this work, two solid solutions of β-La0.9–xCe0.1TbxB5O9 (0 ≤ x ≤ 0.15) and β-La0.9–yCe0.1DyyB5O9 (0 ≤ y ≤ 0.07) were prepared by sol–gel method with high crystallinity, and the phase purity was confirmed with careful analyses on powder X-ray diffraction patterns. Energy transfers are expected due to the overlapping of Ce3+ emission with the Tb3+/Dy3+ excitation. Indeed, the steady photoluminescence spectra indicate the decrease of the Ce3+ emission and the increase of the Tb3+/Dy3+ emission, and the fluorescence decay curves exhibit the decrease of the average lifetime of Ce3+. The energy transfer efficiency is estimated to be 60% at x = 0.15 and 55% at y = 0.07, respectively. The mechanism is likely through the dipole–dipole electric interactions for both cases. With this rationale, the Tb3+ and Dy3+ emissions are greatly enhanced, in particular, the white emission of Dy3+ in β-La0.85Ce0.1Dy0.05B5O9 is enhanced by 20 times.  相似文献   

2.
In this work,calcium niobium gallium garnet(Ca3 Nb1.6875Ga3.1875O12-CNGG) ceramic samples singledoped with Tb3+ and co-doped with Tb3+ and Yb3+ ions were sintered by the solid-state reaction method.The structural characterization of the samples was carried out by X-ray diffraction measurements.The optimal concentration of Tb3+ ions corresponding to the maximum luminescence in the green spectral range in CNGG:...  相似文献   

3.
In this work,combustion synthesis was used for the first time to fabricate a phosphor material with red emission for applications in solid-state white-light lamps.We synthesized a material with emission wavelength at λem=617 nm,excited under long UV-blue wavelength based on Eu3+,Tb3+-activated molybdates Li3Ba2(La1-x-yEuxTby)3(MoO4)8 with 0 ≤ x ≤1 and 0 ≤ y ≤ 1.A series of pow...  相似文献   

4.
Tb~(3+),Dy~(3+)-co-doped Ca_9 Tb_xDy_(1-x)(PO_4)_5(SiO_4)F_2 phosphors were prepared via high-temperature solidphase reaction method and the potential application in optical temperature measurements due to their color-tunable property was investigated in detail.The photoluminescence emission(PL) and photoluminescence excitation(PLE) spectra results show that the as-prepared phosphors exhibit both Tb~(3+) and Dy~(3+) emissions at 546 nm(~5 D_4-~7 F_5 transition of Tb~(3+)) and 587 nm(~4 F_(9/2)-~6 H_(13/2) transition of Dy~(3+)) upon376 nm excitation,respectively.In addition,the fluorescence decay analysis shows that the lifetime of the Tb3+emission rapidly decreases,which confirms the energy transfer existence between Dy~(3+) and Tb~(3+).Under 376 nm excitation,the temperature dependence of the fluorescence intensity ratios for the dualmission bands peaked at 546 and 587 nm was studied in the temperature range from 303 to 573 K.The results show that with the increase of Dy~(3+) concentration,the relative sensitivity first increases and then decreases,what's more,the maximum relative sensitivity is 3.142×10~(-3)%/K for Ca_9 Tb_xDy_(1-x)(PO_4)_5(SiO_4)-F_2(x=0.4).As a consequence,this preliminary study provides a novel method for exploring the novel thermo meters.  相似文献   

5.
Rare earths-doped oxyfluoride glasses based on germanium oxide and lead fluoride were prepared from commercial raw materials. The glasses with general composition of 50GeO2-(50-x-y)PbO-yPbF2-xLnF3 (Ln=Pr3+-Yb3+), contained different concentrations of optically active dopants (x=0.2 mol.% and 2 mol.%) and PbF2 (y≤15 mol.%). The differential thermal analysis (DTA) was used to determine both thermal characteristic and thermal stability properties of the glasses in the function of the kind of dopant, its concentration, and a glass composition. Characteristic glass temperatures such as glass transition temperature (Tg), glass crystallization temperature (Tc) and temperature corresponding to the maximum of the crystallization rate (Tpc) were evaluated. On the basis of obtained results, the thermal stabilities of glasses under study were evaluated using various thermal stability criteria (Dietzel factor ?T, Saad-Poulain factors H' and S). It was found that the increase in rare earth fluoride contents influenced thermal characteristics when the characteristic temperatures of the individual glass was shifted towards higher values. The effect of the PbF2 content and the kind of rare earth impurity on the glass stability was observed. Absorption spectra of lanthanide-doped glasses were measured at room temperature and used to determine the phenomenological intensity parameters Ωt and next, to estimate radiative properties of lanthanide ions in this matrix. Radiative transition probabilities of luminescent states of Ln3+, branching ratios and radiative lifetimes were determined. The variation of the Ωt along the lanthanide series was presented and discussed.  相似文献   

6.
A series of fluorotellurite glasses based on(81–x)Te O2-(10+x)KF-9La2O3(TKL), where x=0 mol.%, 5 mol.%, 10 mol.%, 15 mol.%, doped with 2000 ppm Tm2O3, were prepared by the conventional melt quenching method.The influence of KF content on the thermal stability and optical spectroscopic properties of the Tm3+ doped fluorotellurite glasses were investigated by differential scanning calorimetry(DSC), X-ray diffraction(XRD), density measurement, Fourier transform infrared spectroscopy(FTIR), UV-VIS-NIR optical spectroscopy and fluorescence spectroscopy.Judd-Ofelt intensity parameters of Tm3+ in as-prepared glasses were determined and used to calculate the spontaneous emission probabilities and the radiative lifetime for the 4f-4f transitions of the Tm3+ ions.Stimulated emission cross sections in the 1470 nm region(σse) were evaluated by Füchtbauer-Ladenburg formula.The results showed that KF substitution of Te O2 was beneficial to improving the thermal stability, decreasing glass density and reducing the content of OH related groups for the investigated fluorotellurite glasses.The glass with composition of 66 Te O2-25KF-9La2O3(named TKL25) had the longest radiative lifetime of the 3H4(361 μs) and the largest FWHM×σse value(420.07×10–28 cm3), which made it a promising material for S-band fiber amplifiers.  相似文献   

7.
Europium(Eu~(3+)) doped glasses of chemical compositions(55-x)B_2O_3:10 SiO_2:25 Y_2O_3:10CaO:xEu_2O_3,where x denotes mol% and ranges 0≤ x ≤ 2.5, were synthesized by adopting conventional melt quenching technique, Physical properties like density, molar volume, polaron radius, inter-ionic distance and field strength of the glass samples were investigated to assess the impact of Eu_2O_3. Optical and luminescence properties of the glasses were characterized with optical absorption, photoluminescence,X-ray induced emission spectra, temperature dependence emission spectra and decay times. Judd-Ofelt(JO) intensity parameters(Ω_λ) of the glasses were evaluated based on the absorption spectrum of 0.5 mol%. JO parameters, calculated from absorption spectra with thermal corrections on oscillator strength, were used to evaluate radiative properties such as radiative transition probability(A_R),branching ratio(β_R), stimulated cross section emission(σ) and radiative lifetime(τ_R) for ~5D_0→~7 F_J(J = 0,1,2,3 and 4) transitions. The decay rate of ~5D_0 fluorescent level for all the glass samples was single exponential. Lifetimes of the ~5D_0 level were decreased with increasing concentrations of Eu~(3+)ions from 0.05 mol% to 2.5 mol% which might be due to energy transfer through cross-relaxation in the glasses. The chromaticity coordinates(x, y) were similar for all BSYCaEu glasses and were located at the red region of CIE 1931 color chromaticity diagram. Hence, these results confirm that the Eu~(3+) doped BSYCaEu glasses could be useful for visible red lasers and glass scintillation applications.  相似文献   

8.
A series of energy storage phosphors,Lu_2O_3:Tb,M(M=Hf,Zr,Ti),were investigated by means of photoand thermoluminescence techniques to compare the effect of the co-dopant from the same group of periodic table of elements on charge carriers trapping capability and trap parameters.Most of the investigated processes were tracked individually for the Tb~(3+) in the two different metal sites offered by the Lu_2O_3 host-noncentrosymmetric C_2 and centrosymmetric C_(3i).It is proved that both Tb~(3+)ions participate in hole trapping and electrons are immobilized in traps whose depths are defined by the codopant.Deepest traps,~1.79 eV,appear upon Ti addition,while Zr and Hf generate traps of very similar,~1.40-1.44 eV,depths.The stored energy may be released not only by means of thermal stimulation but also upon the impact of optical photons.Light from the 390-430 nm range of wavelengths was found the most efficient in the latter process.Also deep red radiation of 780 nm releases most of the trapped electrons in Zr/Hf co-doped ceramics but is much less effective in the case of Tb,Ti material.Consistent scheme of electronic levels engaged in charge carriers trapping and subsequent generation of thermoand optically stimulated luminescence was constructed.  相似文献   

9.
The nanocrystalline samarium substituted Co-Zn ferrites with chemical formula Co_(0.7)Zn_(0.3)SmyFe_(2-y)O_4(where y=0,0.01,0.02,0.03,0.04) were synthesized by sol-gel autocombustion route.The analysis of Xray diffractograms(XRD) reveals the formation of cubic spinel structure.The planes indexed from XRD analyses were confirmed in the selected area electron diffraction(SAED) image of the sample.Nanocrystalline nature of the particles in the ferrite samples was confirmed by TEM.The morphology was analyzed by scanning electron microscopy(SEM).Magnetic measurements show an increase in the magnetization for x ≤0.03.The decrease in magnetization due to spin canting is observed for x=0.04.The coercivity depends on Sm~(3+)doping concentration,grain size and saturation magnetization.The complex permeability of the ferrites was analyzed as the function of frequency and Sm~(3+)composition(y).The real part of complex permeability varies linearly with the grain size.  相似文献   

10.
This study fully investigated the vacuum ultraviolet excitation spectra of pure and rare-earth(RE=Eu, Tb and Dy)-doped A2Zr(PO4)2(A=Li, Na and K) phosphors. The synthesized Na and Li compounds were characterized by XRD showing two new types of phases after indexation. Although these three pure compounds had different crystal structures, they exhibited similar luminescence properties. For Eu3+-activated samples, the broad excitation band centered at 217 nm could be attributed to the CT transition between O2–(2p6) and Eu3+ ions. For Tb3+-doped samples, two groups of f-d transitions were observed, where a strong broad band at 221 nm was due to the spin-allowed f-d transition. Energy transfer from O2– to Dy3+was not observed in Dy3+-doped phosphors, probably because it overlapped considerably with the CT transition from O2– to Zr4+ at 187 nm.  相似文献   

11.
In this paper, the Gd2O3:Eu3+,Tb3+phosphors with different doping concentrations of Eu3+and Tb3+ions were prepared by a hydrothermal method for nanocrystals and the solid-phase method for microcrystals. The interaction of the doped ions with different concentrations and the luminescent properties of the nanocrystals and microcrystals were studied systematically. Their structure and morphology of Gd2O3:Eu3+,Tb3+phosphors were analyzed by means of X-ray powder diffraction (XRD), transmission electron mi-croscopy (TEM) and scanning electron microscopy (SEM). The photoluminescence (PL) properties of Gd2O3:Eu3+,Tb3+phosphors were also systematically investigated. The results indicated that when the concentration of doped Eu3+was fixed at 1 mol.%, the emis-sion intensity of Eu3+ions was degenerating with Tb3+content increasing, while when the Tb3+content was fixed at 1 mol.%, the emission intensity of Tb3+ions reached a maximum when the concentration of Eu3+was 2 mol.%, implying that the energy transfer from Eu3+to Tb3+took place. In addition, Tb3+could inspire blue-green light and the Eu3+could inspire red light. Therefore co-doping systems by controlling the doping concentration and the hosts are the potential white emission materials.  相似文献   

12.
A series of single Ce3+ doped and Ce3+ and Tb3+ co-doped Na2BaCa(PO4)2 (NBCP) phosphors was synthesized by conventional solid-stated reaction method. The crystal structure, luminescence properties, thermal stability and energy transfer were carefully investigated. Ce3+ is inferred to substitute the Ba2+ site in NBCP lattice. The color-tunable emission from blue to green is observed by adjusting Tb3+ concentration among NBCP:0.03Ce3+,yTb3+ phosphors. The energy transfer behavior from Ce3+ to Tb3+ ions is both illustrated by co-doped PL spectra and decay curves. The energy transfer efficiency is as high as 91.5%. The mechanism of energy transfer is resonance type of dipole-dipole transition. In this work, the optimal phosphor exhibits the excellent thermal stability which keeps at 94.9% of that initial value at room temperature when temperature reaches to 150 °C. The Ce3+ and Tb3+ co-doped NBCP phosphor is a promising candidate for the application in the general lighting and display fields.  相似文献   

13.
The spectroscopic properties of a series of Dy~(3+) single-doped and Dy~(3+)/Nd~(3+),Dy~(3+)/Tb~(3+),and Dy~(3+)/Tm~(3+)co-doped YAlO_3(yttrium aluminum perovskite,YAP) phosphors were investigated and compared through the measurements of optical absorption,emission spectra,and fluorescence decay curves.For the Dy~(3+) ion single-doped samples,the intensity of each absorption band increases with an increment in Dy~(3+) ion doping concentration,and the identified strong absorption peak at 447 nm indicates that Dy~(3+):YAP phosphors are suitable to be pumped by a blue laser diode(LD).For all co-doped samples,absorption peaks of Dy~(3+) ion along with some of the absorption bands of Nd~(3+),Tb~(3+),and Tm~(3+) ions are observed.Under 351 and 447 nm excitation,a prominent emission peak at 572 nm was obtained in all the samples,corresponding to Dy~(3+):~4 F_(9/2)→~6 H_(13/2) transition.Here,2 at% Dy~(3+):YAP phosphor exhibits the highest yellow emission intensity under 447 nm pumping.Among the three kinds of Dy~(3+) co-doped phosphors,Dy~(3+)/Tb~(3+):YAP phosphor possesses the dominant yellow emission.The fluorescence decay curves show exponential behaviour and are fitted well.The Commission International de L'Eclairage(CIE)chromaticity coordinates were calculated following the respective emission spectra,and it is found that all the coordinates locate in the yellow region.The energy transfer(ET) processes were investigated and the concentration quenching mechanism was discussed.The obtained results suggest that Dy~(3+)-activated YAP phosphors are good candidates for yellow LED applications.  相似文献   

14.
Doped strontium(Sr) hexaferrites appeared potential candidates for microwave absorber applications.Driven by this idea, we examined the influence of manganese(Mn) and yttrium(Y) co-substitution on the microstructures,morphology and magnetic properties of Sr nanohexaferrites(Sr_(1-x)Mn_xFe_(12-y)Y_yO_(19),where 0.0 ≤ x = y ≤ 0.5) synthesized via citrate sol-gel auto-combustion technique. As-prepared samples were thoroughly characterized using diverse analytical tools. X-ray diffraction pattern reveals a single Mhexagonal crystalline phase. FE-SEM, TEM, HR-TEM show a hexagonal platelet-like structure. The magnetic hysteresis loops(measured at room and low temperature) of the as-prepared nanohexaferrites exhibit ferromagnetic(FM) behavior. Magnetic parameters including the saturation magnetization,remanence, coercive and magneto-crystalline anisotropy field are found to decrease with the increase in Mn~(2+) and Y~(3+) contents. Zero-and normal-field cooled magnetization measurements in the range of 2-400 K display the complete absence of blocking temperature, confirming the characteristic ferromagnetic behavior of the proposed composition.  相似文献   

15.
Cathodoluminescent properties of Tb^3+-doped yttria nanocrystallites   总被引:1,自引:0,他引:1  
The Tb3+-doped Y2O3 nanopowders were synthesized using the modified Pechini method. The average size of nanocrystallites was controlled by different sintering temperatures. The structure and morphology of obtained nanopowders were examined using the XRD and SEM analyses. The Cr:Al2O3 was mixed with Tb3+:Y2O3 powders and its normalized emission was used to measure a relative intensity of Tb3+:Y2O3. The mixtures were electrophoretically deposited on ITO-glass slides. The cathodoluminescence spectra of obtained layers were recorded and analysed. The discussion over an influence of average grains size on phosphor efficiency was presented.  相似文献   

16.
Eu~(3+) activated and Eu~(3+), Tb~(3+) co-activated monodisperse sodium double tungstates NaGd(WO4)2 phosphors were prepared by molten salt method at 750 ℃ for 10 h using NaCl as a flux. The crystal structure and morphology of the as-synthesized phosphors were measured by XRD and SEM, respectively. The photoluminescence properties were characterized by PL spectra, decay lifetime and CIE. The presence of NaCl plays an important role in the morphology and luminescence properties. In this work,NaCl and one of the raw material Na_2 CO_3 in a certain proportion will form a low eutectic salt to decrease the reaction temperature and benefit the formation of monodisperse NaGd(WO_4)_2 crystals. The color of Eu~(3+) and Tb~(3+) co-doped NaGd(WO_4)_2 phosphors can be tuned from creamy white to orange, red and green by adjusting the doping concentration of rare earth ions, since the emission contain the broad blue-green emission origin from NaGd(WO_4)_2 host and characteristic red and green emission origin from Eu~(3+) and Tb~(3+) ions. The electroluminescent spectra and CIE measurement shows that the LED device with NaGd_((1-x))(WO_4)_2:xEu~(3+)(x = 0.24) phosphor can be excited by 365 nm and 380 nm LED chip, and their CIE coordinate is(x = 0.45, y = 0.45) and(x = 0.36, y = 0.37), Ra is 80.3 and 86.3, T_c is 3196 and4556 K, respectively. As a single-component phosphor, NaGd(WO_4)_2:Eu~(3+),Tb~(3+) have potential application in UV-pumped WLEDs.  相似文献   

17.
Tri-doped Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors were prepared by a high-temperature solid state method.Under UV light excitation,Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+)samples exhibit a broad band ranging from 320 to 500 nm.At 77 K,the emission spectra of Ca_9 LiY_(2/3)(PO_4)7:Ce~(3+)samples present two obvious emission peaks,indicating that Ce~(3+)ions occupy two different kinds of lattice sites(Ca(1/2) and Ca(3)),As a good sensitizer for Tb~(3+),Ce~(3+)ions in Ca_9 LiY_(2/3)(PO_4)_7 lattice can effectively transfer part of energy to Tb~(3+),and the energy trans fer mechanism is determined to be dipole-dipole interaction.Consequently,the emitting color for Ce~(3+) and Tb~(3+) co-doped Ca_9 LiY_(2/3)(PO_4)_7 samples can be tuned from bluish violet to green.In order to further enlarge the emission gamut,Mn~(2+)ions as red emission components were added,forming tri-doped single-phase Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors.The Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors exhibit tunable emission properties through controlling the relative doping concentration of Ce~(3+),Tb~(3+)and Mn~(2+).Especially,Ca_9 LiY_(2/3)(PO_4)_7:0.09 Ce~(3+),0.12 Tb~(3+),0.30 Mn~(2+)can emit warm white light.The sample shows good thermal stability.At 150℃,the emission intensity for Ce~(3+)(360 nm),Tb~(3+)(545 nm) and Mn~(2+)(655 nm) decreases to 63%,69%,and 72% of its initial intensity,respectively.Moreover,the sample obtains good stability after 10 cycles between room temperature and150℃.  相似文献   

18.
Effect of rare earth oxide Tb2O3 additive on transformation behavior and grain growth of anatase and photocatalytic activity for TiO2/(O′ +β′)-Sialon multi-phase ceramic was investigated and the mechanism was discussed. X-ray diffractometer (XRD) was employed for the analysis of phase composition, grain size and lattice parameters of anatase. Photocatalytic activity of the composites was investigated through its photocatalytic degradation to methylene blue (MB) solution. The results showed that Tb2O3 significantly inhibited the transformation process, which displayed an appreciably intensified effect with increasing Tb2O3 content. It could be attributed to the coaction of the active and passive influence mechanisms. For Tb3+ entering TiO2 lattice, replacing Ti4+ accelerated the transformation, whereas the lattice distortion caused by it was unfavorable for the process. On the other hand, the redox reaction between Tb3+ and TiO2 as well as the Tb2O3 deposited on the surface of TiO2 inhibited the transformation. The addition of Tb2O3 effectively restrained the grain growth of TiO2 and the effect became significant with the increase of its content. With the increase of Tb2O3 addition, the photocatalytic activity of the catalysts increased and then dropped after reaching the maximum at about 2%. The action mechanism of Tb2O3 could be attributed to its optical properties and its effect on phase transformation, grain growth and crystal structure of TiO2.  相似文献   

19.
YbPO4:Tb3+ were synthesized by mild hydrothermal method. The luminescent properties, morphologies and structure of the obtained powders were characterized by photoluminescence (PL) spectra, FESEM, X-ray diffractometer (XRD) and FTIR. The results showed that the prepared YbPO4:Tb3+ nanoparticles were pure tetragonal phase and the average grain size varied with increasing of Tb3+ concentration. Hydrothermal temperature was revealed to be the key factor to enhance the emission intensity of YbPO4:Tb3+ phosphors. The spherical nanoparticles could be effectively excited by near UV (369 nm) light and exhibited green performance at 543 nm (5D47F5), 489 nm (5D47F6) and 586 nm (5D47F4). The CIE chromaticity was calculated to be x=0.298, y=0.560. The YbPO4:Tb3+ nanoparticles exhibited potential to act as UV absorber for solar cells to enhance the conversion efficiency.  相似文献   

20.
A green long persistent luminescence (LPL) phosphor Ca3Ga4O9:Tb3+/Zn2+ was prepared. Ca3Ga4O9 matrix exhibits blue self-activated LPL due to the creation of intrinsic traps. When Tb3+ is doped, the photoluminescence (PL) and LPL colors change from blue to green with their intensities significantly enhanced. The doping of Zn2+ evidently improves the PL and LPL performances of the Ca3Ga4O9 matrix and Ca3Ga4O9:Tb3+. The thermoluminescence (TL) spectra show that a successive trap distribution is formed by multiple intrinsic traps with different depths in the Ca3Ga4O9 matrix, and the incorporation of Tb3+ and Zn2+ effectively increases the densities of these intrinsic traps. The existence of a successive trap distribution makes the Ca3Ga4O9:Tb3+/Zn2+ phosphor exhibit thermally stable PL and LPL. It is indicated that this phosphor shows great promise for the application such as high-temperature LPL phosphor.  相似文献   

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