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1.
A series of Ln3+ (Ln3+ = Er3+/Dy3+) ions doped Na2NbAlO5 (NNAO) phosphors were synthesized by solid-state method. The Er3+ and Dy3+ ions doped phosphors were characterized by XRD, photoluminescence (PL) and decay profiles. The Ln3+-doped samples are consistent with the pure NNAO phase which is analyzed by the X-ray diffraction result. The PL graphs show that the intensity of luminescence increases with the increasing doping concentrations up to their critical certain values and then decreases at higher concentrations due to the concentration quenching effect of Er3+/Dy3+ ions. The energy level diagrams containing the positions of 4f and 5d energy levels of Er3+ and Dy3+ ions have been established and studied. In addition, under the ultraviolet light, the prepared NNAO:xLn3+ (Ln3+ = Er3+/Dy3+) phosphors show the characteristic green (Er3+), cyan (Dy3+) emission, respectively. Under the excitation of 365 nm, the quantum efficiencies of NNAO:0.01Er3+ and NNAO:0.03Dy3+ phosphors are measured to be 61.7% and 72.2%, respectively. The obtained results indicate that the new NNAO:xLn3+ (Ln3+ = Er3+/Dy3+) phosphors are promising applications in white-light emitting diodes field.  相似文献   

2.
Energy transfer among the co-doped activators is an efficient route to achieve color-tunable emission in inorganic phosphors.Herein,photoluminescence tuning from blue to cyan has been achieved in the Lu2MgAl4 SiO12;Eu^2+,Ce^3+phosphors by varying the Ce^3+concentration with a fixed Eu^2+content.With the further introduction of a Mn^2+-Si^4+couple into the host lattice,the emission color can be tuned to red through the energy transfer of Eu^2+and Mn^2+.The luminescence properties and the energy transfer mechanism were studied in detail.The energy transfer from Eu^2+to Ce^3+is certified as a dipolequadrupole interaction with the energy transfer efficiency of 41.4%and Eu^2+to Mn^2+belongs to a dipole-dipole interaction with the energy transfer efficiency of 94.3%.The results imply that this singlephased Lu2MgAl4 SiO12:Eu^2+,Ce^3+,Mn^2+phosphor has a potential prospect for application in near-UV chip pumped white light emitting diodes.  相似文献   

3.
Ball milling method was applied to prepare Lu~(3+)/TiO_2 photocatalysts. The catalysts were characterized with X-ray powder diffraction(XRD), X-ray photoelectron spectroscopy(XPS), UV-visible diffuse reflectance spectra(UV-vis DRS), energy dispersive X-ray spectrometer(EDS), transmission electron microscopy(TEM) and Brunauer-Emmett-Teller(BET) method. The photocatalytic activities were determined by the degradation of methylene blue(MB) equipped with a 300 W medium pressure mercury lamp. Results show that the first order reaction rate constants of Lu~(3+)/TiO_2 and pure TiO_2 are0.0565 and 0.0263 min-1, respectively, which both were evaluated under the condition of catalysts loading of 0.2 g/L,initial concentration of 25 mg/L for MB, mole ratio of Lu~(3+)/TiO_2 of 1.5% and milling time of 4 h. The average crystal sizes of 1.5 mol% Lu~(3+)/TiO_2 and pure TiO_2 are 18.7 and 19.3 nm, respectively.  相似文献   

4.
The precipitation of the water-leaching solution of Baotou mixed rare earth(RE) concentrate roasted with sulfuric acid using ammonium bicarbonate for producing RE carbonate produces a mass of ammonia-nitrogen wastewater because of the relatively low solubility of rare earth sulfate.To solve the serious problem of ammonia-nitrogen pollution,new precipitators need to be developed urgently so as to meet the requirements of environmental protection and impurities content of the product(SO_4~(2-)1.8 wt% in RE carbonates products).In this paper,we studied the effects of feeding modes on the behavior of SO_4~(2-) during the preparation of light RE carbonate(RE=La,Ce,Pr,Nd) from their sulfate solutions using Mg(HCO_3)_2 as a precipitant.The results indicate that the contents of SO_4~(2+) in the La and Ce precipitates using positive feeding mode exceed 16 wt% because of the formation of La2(CO_3)_(2.15)(-SO_4)_(0.85)·4 H_2 O and Ce2(CO_3)_(2.15)(SO_4)_(0.85)·3 H_2 O,while those of the Pr and Nd precipitates are 4 wt%-5 wt%since they exist in the form of n-carbonate.The precipitates prepared using synchronous feeding mode are all RE carbonate with only 4 wt%-5 wt% of SO_4~(2-) enclosed in the precipitation.The content of SO_4~(2-) in the RE carbonate obtained using reverse feeding mode is the lowest.Among them,the content of SO_4~(2-) in La precipitate is only 1.40 wt%.Both synchronous and reverse feeding modes can effectively reduce the content of SO_4~(2-)in RE carbonate,which provides theoretical guidance for the preparation of qualified light RE carbonate products by Mg(HCO_3)_2 precipitation method.  相似文献   

5.
CePO4:Tb3+ nanorods were successfully obtained via a simple hydrothermal method and combined with carbon dots (CDs) to obtain CDs@CePO4:Tb3+ nanorods. Due to the combination of CDs, the emission intensity of CDs@CePO4:Tb3+ nanorods increases about 92 times, compared with that of CePO4:Tb3+ nanorods. The combination of CDs and CePO4:Tb3+ nanorods was confirmed by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and so on. The mechanism of luminescence enhancement may be attributed to some aspects: the formation of hexagonal phase results in the increase of crystal field symmetry, and the energy transfer among CDs, Ce3+ and Tb3+ ions, which causes the Tb3+ ions in CDs@CePO4:Tb3+ nanorods to obtain more excited energy and less non-radiative attenuation compared to CePO4: Tb3+ nanorods. The luminescence enhancement strategy through combination of CDs would provide a simple and effective approach for other rare earth ions doped luminescent materials.  相似文献   

6.
This review focuses on the recent research progress in the multi-component assembly of luminescent rare earth hybrid materials, which is based on the luminescent rare earth compounds and two or more other building units, including the other photoactive species. It covers the multi-component luminescent rare earth hybrids which was assembled with different (a) organic-inorganic polymeric units, (b) nanoporous units, (c) nanoparticle composites or (d) other developing special units. Finally, future challenges and opportunities in this field are discussed. Herein it mainly focuses on the work of Yan's group in recent years.  相似文献   

7.
Rare-earth modification Bi_2 WO_6 composites(RE/Bi_2 WO_6) were studied by experimental performance and theory computation based on the different 4 f orbits of selected rare earth elements(La,Ce,Gd,and Yb).The prepared RE/Bi_2 WO_6 was characterized by XRD,SEM/TEM,XPS,UV-vis DRS,and N_2 adsorption to learn their physical-chemical properties.Azo dye Rhodamine B(RhB) was photodegraded as a target pollutant to investigate the photocatalytic activity of prepared RE/Bi_2 WO_6 composites.The results of experiment and computation show that four rare earth elements with different electron configurations retain the phase and morphology of Bi_2 WO_6 and enhance the removal efficiency of RhB under simulated solar irradiation.The optimum doping contents are 0.01%,0.05%,0.05% and 0.01% for La-,Ce-,Gd-,and Yb-doped Bi_2 WO_6,respectively.However,light rare earth La and Ce doped composites indicate some difference in visible light adso rption capacity and mineralization on RhB co mpared with heavy rare earth Gd and Yb doped composites.Both La/Bi_2 WO_6 and Ce/Bi_2 WO_6 possess larger pore size and higher mineralization ability than Gd/Bi_2 WO_6 and Yb/Bi_2 WO_6 under the same experimental conditions while Gd/Bi_2 WO_6 and Yb/Bi_2 WO_6 show stronger red shift to the visible light due to the more 4 f electrons.The hole oxidation plays a major role in the photodegradation of RhB by all RE/Bi_2 WO_6.  相似文献   

8.
In acid treatment technology of Baotou mixed rare earth ore,large quantities of ammonia-nitrogen wastewater are produced in the step of ammonium bicarbonate precipitation to transform rare earth sulfate.In this paper,we adopted a green precipitant magnesium bicarbonate(Mg(HCO3)2) to substitute ammonium bicarbonate to eliminate ammonia-nitrogen pollution.The effects of n(HCO3-):n(RE3+),aging temperature and aging time on the crystallization u...  相似文献   

9.
White-light-emitting phosphors based on phosphate host matrix, KSrPO_4 doped with Dy~(3+), were prepared by solid state reaction and their VUV luminescent properties were firstly investigated. The excitation band peaking at 125-153 nm corresponding to the absorption of PO_4~(3-) group exhibits very strong absorption. The phosphors emit warm-white luminescence under vacuum ultraviolet excitation of 147 nm, which consists of three main emission peaks located at 475, 570 and 662 nm, respectively.According to the luminescence and color chromaticity of the optimal sample KSrPO_4:1 mol%Dy~(3+),1.3 mol%Li~+, it can be a potential candidate for mercury-free fluorescent lamps.  相似文献   

10.
Nanosized 1 at% Sm3+doped Y2O3 powders were prepared by an ultrasound assisted sol-gel method.Y2O3:Sm3+powders crystallize in Y2 O3 pure cubic phase and XRD analysis shows that the as-used agitation protocol affects strongly the crystallite’s shape and mean size.The recorded emission spectra under λem=600 nm exhibit two absorption bands;the first one is assigned to O2-→Sm3+cha...  相似文献   

11.
Nowadays,it is concern for researchers that due to high recombination rate of photogenerated charge carriers in tungsten trioxide(WO3) nanoparticles,the future applications are limited in the field of photocatalysis.Herein we attempt to synthesize tungsten trioxide nanoparticles with different doping concentrations of lanthanum i.e.2 wt%,4 wt%,6 wt% and 8 wt%.The synthesized samples were characterized by using various characterization techniques:X-ray diffraction(XRD),Raman spectrosco...  相似文献   

12.
Gd~(3+)/TiO_2 and Gd_2O_3/TiO_2 nanoparticles were prepared by ball milling method.The effects of Gd~(3+)ion and Gd_2O_3 on the structure and optical property of TiO_2 were studied by XRD and UV-vis DRS.Specific surface area was determined by Brunauer-Emmett-Teller(BET)method.The morphology and elemental composition were characterized by SEM-EDS.XPS was used to determine the surface compositions and chemical character of elements.The sample sizes and microstructures were observed by TEM.The photocatalytic activities of TiO_2 nanoparticles modified with rare earth metal gadolinium(Gd~(3+)ion or Gd_2O_3)were evaluated by degradation of methylene blue(MB)under UV light.Experimental results indicate that 2,5 mol%Gd~(3+)/TiO_2 shows the best photocatalytic activity compared with Gd_2O_3/TiO_2 and pure TiO_2.The existence of gadolinium can exhibit the aggregation and induce lattice distortion of TiO_2 obtained from XRD,SEM and TEM results.The band gap energy of 2.5 mol%Gd~(3+)/TiO_2 decreases to3.07 eV and it leads to visible light absorption response which can be seen from UV-vis absorption spectra.The surface area of 2.5 mol%Gd~(3+)/TiO_2 equals to 85.8 m~2/g and average crystal size is 21.1 nm.EDS and XPS analyses reveal that gadolinium can be introduced either into TiO_2 lattice or adsorbed on the surface of TiO_2.The content of surface OH groups in 2.5 mol%Gd~(3+)/TiO_2 is 50,88%(1.55 times higher than that of pure TiO_2)and the content of lattice oxygen decreases to 11.26%.The MB(25 mg/L)degradation reaction rate constants of 2,5 mol%Gd~(3+)/TiO_2,0.5 mol%Gd_2O_3/TiO_2 and pure TiO_2 were0.0713,0.0588 and 0.0263 min~(-1),respectively.The degradation rates of rhodamine B(30 mg/L)in 60 min are 97,9%,90.1%and 84.6%for 2,5 mol%Gd~(3+)/TiO_2,0.5 mol%Gd_2O_3/TiO_2 and pure TiO_2,respectively.  相似文献   

13.
Ion adsorption type rare earth ores (IATREOs) are a valuable strategic mineral resource in China, which feature a complete composition of fifteen rare earth elements and are rich in medium and heavy rare earth (RE) elements. In the leaching process for recovering rare earth elements from IATREOs, many impurities will be leached together with rare earth elements and enter the leaching liquor. An impurity removal-precipitation enrichment technique is currently applied to selectively recovery rare earth elements from the leaching liquor with the high content of impurities and low concentration of rare earth elements by using ammonium bicarbonate in the industry. However, a high loss of rare earth elements and severe ammonia nitrogen pollution are caused by this process. Therefore, more beneficial impurities removal technologies, mainly for aluminum, and green enrichment technologies with lower pollution are now urgently needed. For this purpose, this paper analyzed two aspects of research progress in recent decades: the green separation of rare earth elements and aluminum from leaching liquor and the green and efficient enrichment of rare earth elements. Finally, an approach for the high-efficiency and green enrichment of rare earth elements from leaching liquor of the IATREOs is proposed in several aspects, including impurity inhibition leaching, neutralization and impurity removal, alkaline calcium and magnesium salt precipitation enrichment, and centrifugal extraction enrichment.  相似文献   

14.
Ytterbium and rare earth ions(RE=Y,Gd,La)codoped CaF2-SrF2single crystals(3 at%Yb,6 at%RE:CaF2-SrF2)were fabricated by temperature gradient technology(TGT).All the space groups remain the same Fm3m as that of Yb:CaF2-SrF2.The lattice parameter a,unit cell volume V,as well as bond length of Ca/Sr-F and F-F increase in the sequence of rare-earth ions radius Y3+3+3+.The segregation coefficients of Yb ions are 0.87 in Yb,La:CaF2-SrF2and Yb,Gd:CaF2-SrF2,which are larger than 0.85 in Yb,Y:CaF2-SrF2and 0.80 in Yb:CaF2-SrF2.Absorption spectra in the range of 200 and 400 nm were analysed with Yb2+contents.The absorption and emission cross-sections in the range of 900-1100 nm were determined together with fluorescence lifetime.The saturation pump density/Sat,minimum pump density/m in and gain cross-section were analysed.Yb,La:CaF2-SrF2has a relatively higher optical parameter(δem×t,0.52×1020cm2·ms),lower Isat(3.68 kW/cm2)and^min(0.50 kW/cm2)at 1038 nm indicating the potential application in high power laser.Low phonon energy of CaF2-SrF2is 302 cm-1which is located between those of CaF2and SrF2as measured by Raman spectra.It is believed that ytterbium and rare earth ions(RE=Y3+,Cd3+,La3+)codoped CaF2-SrF2eutectic solid-solution is promising for high-power and wavelength-tunable solid-state lasers.  相似文献   

15.
Rare earth(RE) plays a unique and irreplaceable important role in iron and steel.The developments in both basic research and application of RE steel are rapid in recent years.Especially, RE electrical steels attracts more and more attention.However, the relevant research is still in the exploration stage, and it is urgent to carry out systematic and in- depth research work. Based on the recent research results about the application of RE in electrical steels, the research status of RE in electrical steels under modern technical conditions and the effect mechanism of RE in electrical steels were summarized. The application of RE in conventional non- oriented electrical steels, grain- oriented electrical steels and Fe- 6. 5 mass% Si high- silicon electrical steels were discussed respectively. A large number of studies show that the addition of RE in electrical steels can significantly improve the magnetic properties, mechanical properties and texture of electrical steels.There is a broad application prospect of RE in the improvement of magnetic and mechanical properties for electrical steels, and the development of RE electrical steels with Chinese resources?? characteristics has an important academic value and a practical significance.  相似文献   

16.
Solution equilibrium calculations were performed in this study to understand the impact of contaminant metal ions on the precipitation efficiency of selected ra...  相似文献   

17.
Mineral liberation analyser (MLA) was applied to quantitatively analyze the rare earth ore from Weishan in Shandong. Mineralogy parameters, such as mineral composition, occurrence states of rare earth elements (REEs) and valuable elements, mineral embedded grain size distribution, mineral association and liberation, are obtained. Results show that the contents of REEs and other valuable elements mainly contained in the ore were La 1.02 wt%, Ce 4.29 wt%, Pr 0.34 wt%, Nd 0.84 wt%, Sr 3.4 wt% and Ba 26.53 wt%, respectively. The REEs mainly occur in bastnaesite and carbocernaite in the form of independent mineral and the contents of bastnaesite and carbocernaite in the ore were 5.96 wt% and 12.30 wt%, respectively. 67.34% of strontium occurs in carbocernaite and the rest occurs in celestobarite and strontianite mineral. 92.71% of barium occurs in barite. Liberation of main rare-earth minerals such as bastnaesite and carbocernaite is more than 80% when the grinding fineness is 78.42% passing 74 μm. The research results could be employed to provide detailed basic theoretical data for further improvement of the beneficiation process flow and the processing index of rare earth ore, the recycling of other valuable minerals and the comprehensive utilization of tailings.  相似文献   

18.
Six binuclear rare earth compounds were synthesized through the ligand of 4-Bromo-N-hydroxy-N-methyl-benzamide (sH2bha). Compounds 13 are isomorphous, and compound 1 is crystallized in the monoclinic system with the P21/c space group. Compounds 4 and 5 are isomorphous, and compound 4 is crystallized in the triclinic system with the P-1 space group. Compound 6 is crystallized in the triclinic system with the P-1 space group. The compounds were characterized by thermogravimetric analysis (TGA) and IR spectroscopy. The fluorescence spectrum in the visible area shows characteristic peaks of Eu, Tb, and Dy compounds. The efficiency of Eu compound on the viability of PC3 cells was assessed using CCK8 assays. From the CCK8 results, ionic concentration may have a great effect on PC3 cells' proliferation. Eu compound shows red fluorescence in the cytoplasm of PC3 cell. As for Eu compound, it might have potential application in cell imaging technology.  相似文献   

19.
The MnXOx catalysts(i.e.,MnSmOx,MnNdOx,MnCeOx) were prepared by reverse co-precipitation method and used for NH3-SCR reaction.It is found that MnCeOx catalyst presents the best low tempe rature catalytic activity(higher than 90% NOx conversion in the te mperature range from 125 to 225℃)and excellent H2O+SO2 resistance.In order to explore the reason for this result,the characterization of X-ray diff...  相似文献   

20.
Recovery of rare earth (RE) elements from Nd-Fe-B waste is one of the ways to solve the problem of so-called RE-crisis. An alternative approach of extracting RE elements from Nd-Fe-B waste by molten Cu extraction based on liquid-solid diffusion and reaction is reported in this paper. The extraction process, product microstructure and extraction efficiency were systematically studied. The results show that the extraction rate of RE at 1200 °C is about 20% higher than that at 1100 °C. The enhanced extraction efficiency at 1200 °C results from the fact that the liquid Fe and Fe2B are not co-soluble with Cu. Reducing the mass ratio of Cu to waste and the size of the waste scraps is also beneficial to enhancing the separation of RE and Fe elements. In addition, the extraction time should be well controlled, for example, less than 2 h at 1100 °C, in order to avoid the increased Fe content in the extracted product. Based on optimized process, the RE elements can be almost fully extracted from the waste. This work thus provides an effective method to recover the RE elements.  相似文献   

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