查看更多>>摘要：CeCO3OH has a unique crystal structure and excellent optical,electronic and catalytic properties,which has been widely investigated for many applications.Interestingly,ceria obtained from CeCO3OH has a morphology that is similar to that of the precursor,and the CeO2-based products obtained from CeCO3OH exhibit outstanding properties,such as catalytic performances,owing to their designed morphology and oxygen vacancies(OVs).To introduce CeCO3OH into a wider range of potential researchers,we first systematically review the physico-chemical properties,synthesis,reaction and morphology tuning mechanism of CeCO3OH,and summarize the conversion behavior from CeCO3OH to ceria.Then,we thoroughly survey the applications of CeCO3OH and its conversion products.Suggestions for further investigations of CeCO3OH are also made in this review.It is hoped that the exhaustive compilation of the valuable properties and considerable potential investigations of CeCO3OH will promote further appli-cations of CeCO3OH and CeO2-based functional materials.
查看更多>>摘要：Light emitting diode(LED)is the fourth generation lighting source,but it has some shortcomings such as complex chip packaging process and the unbalanced light color of phosphor in long-time application.In this study,a kind of Eu-terephthalic acid/Tb-sulfosalicylate/ZrO2/ZnZrO3(Eu-PTA/Tb-SSA/ZrO2/ZnZrO3)phosphor with warm white light emission properties was prepared,and the warm white light LED(w-WLEDs)was successfully prepared by encapsulating Eu-PTA/Tb-SSA/ZrO2/ZnZrO3 phosphors together with 270 nm UV-chip.The ZrO2/ZnZrO3,Tb-SSA/ZrO2/ZnZrO3 and Eu-PTA/ZrO2/ZnZrO3 samples show blue emission,green emission and red emission under deep ultraviolet(UV,270 nm)excitation,respectively.The Tb-SSA and Eu-PTA are co-doped into ZrO2/ZnZrC3 matrix with blue emission to achieve the warm white light emission,and the light color can be adjusted by controlling the doping amount of Eu3+and Tb3+.Through the excitation method of single-component phosphor by the single chip,the complex chip packaging process of w-LED can be solved.By doping rare earth organic com-plexes into porous ZrO2/ZnZrO3 matrix,the problems of the light color unbalanced of phosphor and the low luminescence intensity of rare earth doped metal oxides composites can be solved.
查看更多>>摘要：With the increasing demand for non-contact fluorescence intensity ratio-based optical thermometry,novel phosphor materials with high-efficiency,dual-emitting centers,and differentiable temperature sensitivity are highly desired.In this work,rare earth Eu2+ions were incorporated into CsCu2I3 microcrystals by solid-state reaction.Under a single UV excitation,the as-synthesized samples exhibit two emissions:452 nm blue emission from the 5d→4f transition of Eu2+and 582 nm yellow emission from self-trapped exciton emission of CsCu2I3.The photoluminescence quantum yield reaches to 50％.The dual-band emission of Eu2+-doped CsCu2I3 shows different temperature responses in the range of 260-360 K.Based on fluo-rescence intensity ratio technology,the maximum absolute sensitivity and relative sensitivity are 0.091 K-1(at 360 K)and 2.60％/K(at 260 K),respectively.These results suggest that Eu2+-doped CsCu2I3 could be a good candidate for highly sensitive optical thermometer.
查看更多>>摘要：Dual-excitation and dual-emission Y4GeO8:Bi3+,Sm3+phosphors were manufactured by traditional solid-phase sintering technique.The X-ray diffraction,morphology,photoluminescence,energy transfer process and temperature sensing properties of Y4GeO8:Bi3+,Sm3+samples were comprehensively evaluated.The Y4GeO8∶Bi3+,Sm3+phosphors exhibit characteristic emissions of Bi3+(3P1→1S0)and Sm3+(4G5/2→6H)under both 290 and 347 nm excitations.In fluorescence intensity ratio and Commission International de L'Eclairage coordinates modes,Y4GeO8:Bi3+,Sm3+samples present excellent temperature measurement performance.The maximum relative sensitivity(Sr-max)values of the former are 1.55％/K(460 K,290 nm excitation)and 0.82％/K(506 K,347 nm excitation).The Sr-max(x)values of the latter are 0.21％/K(437 K,290 nm excitation)and 0.15％/K(513 K,347 nm excitation).These results illustrate that Y4GeO8:Bi3+,Sm3+phosphors can be used as a candidate material for a dual-mode optical thermometer under dual-excitation.
查看更多>>摘要：Phosphor-converted near-infrared light-emitting diodes(NIR pc-LEDs)are finding applications in various fields including food quality analysis,biomedical imaging,night vision,and biomedicine.The crucial factor in the development of NIR pc-LEDs devices lies in the advancement of high-performance broad-band NIR phosphors.In this work,novel Cr3+-activated silicate phosphors NaRESi3O9(RE=Y,Lu,Sc)are reported.This silicate has a special 3D network structure in which RE has four different sites,forming four octahedrons and providing suitable occupation sites for Cr3+.The phosphors demonstrate a wide emission spectrum ranging from 750 to 1450 nm when excited by light at 468 nm.The full width at half maximum(FWHM),which benefits from the presence of Cr3+ions occupying multiple sites,is measured to be 203 nm.Notably,the strongest emission peak is observed at a longer wavelength of 984 nm compared to most other systems activated by Cr3+.The Na3ScSi3O9 lattice provides a weak crystal field(Dq/B=1.97)and weak phonon-photon coupling for Cr3+,and the integrated emission intensity of Na3ScSi3O9∶0.03Cr3+is 4.66 times stronger than that of Na3YSi3O9∶0.03Cr3+.
查看更多>>摘要：Novel orange-red Sr2GdSbO6∶xEu3+(x=0,0.05,0.1,0.2,0.3,0.4,0.5 and 0.6)phosphors were successfully prepared by the traditional high-temperature solid-state method.The results of Rietveld refinement,energy dispersive spectroscopy(EDS)spectrum and elemental mapping demonstrate that Eu3+suc-cessfully replaces the Gd3+sites and distributes uniformly in the particles of phosphors.The lumines-cence properties of Sr2GdSbO6∶Eu3+phosphors were investigated in detail.The emission spectra of the strongest emission peak is the 5D0→7F1(593 nm)transition,which can emit orange-red light under 393 nm excitation.When the doping concentration of Eu3+ions is x=0.2,the luminescence intensity of the phosphors reaches the highest.The detailed mechanism of concentration quenching is attributed to dipole-dipole interaction.The thermal stability values of Sr2GdSbO6∶0.2Eu3+phosphors are 87％,82％and 114％under 393,467 and 527 nm excitations,respectively.The causes of the abnormal thermal quenching under 527 nm excitation were analyzed.Based on the abnormal thermal quenching under 527 nm excitation,the optical thermometry properties of Sr2GdSbO6∶0.2Eu3+phosphors were investi-gated by fluorescence intensity ratio(FIR)technique,and appreciable relative sensitivity was obtained.The results suggest that Sr2GdSbO6∶0.2Eu3+phosphors can be potentially applied to w-LEDs and optical thermometers.
查看更多>>摘要：Highly pure red phosphors LiM(PO3)3∶Eu3+(M=Sr,Ca)doped with Eu3+(1 mol％)were synthesized via solution combustion method and their crystal structure and luminescence dynamics were studied to explore its suitability in white light emitting diodes.The Rietveld refinement analysis of the powder X-ray diffraction patterns reveals that the phosphors belong to the pure triclinic phase of LiSr(PO3)3 and LiCa(PO3)with space group P-1(2).The scanning electron microscopy images showed the agglomerated morphology.The photoluminescence emission spectra under 393 nm show an orange band at 594 nm and a red band at 613 nm ascribed to 5D0 → 7F1,5D0 → 7F2 transitions of Eu3+ion in both the phosphors.Moreover,the spectroscopic properties such as luminescence behaviour,and Stark splitting were used to examine the symmetry of Eu3+ions in LiM(PO3)3∶Eu3+(M=Sr,Ca)phosphors in terms of distortion induced upon doping.The Stark splitting shows that the actual site symmetry for Eu3+ion was estimated to be D2 type for both phosphors.The photometric properties of LiCa(PO3)3∶Eu3+such as Commission International de l'Eclairage coordinates(x=0.64,y=0.36)near to the standard one(red),high color purity(95％)and higher brightness reveal that the phosphor has the capability of acting as a red component in n-UV white light emitting diodes.
查看更多>>摘要：Two novel phosphors LiBa4(1-x)Eu4xTa3O12(H-LBTO∶xEu3+)and Li0.25Ba1-xEuxTa0.75O3(C-LBTO∶xEu3+)were prepared successfully by a molten salt method.The transformation between these two structures was realized by changing the sintering temperature or changing the Eu3+ions concentration,which was also demonstrated by the X-ray diffraction(XRD),scanning electron microscopy(SEM),diffuse reflec-tance spectra(DRS),and photoluminescence excitation(PLE)analyses.Both the sintering temperature and the Eu3+ions doping concentration have significant impact on the formation of the crystal phase.All these phosphors sintered at 1023 K exhibit two major luminescence lines at 594 and 614 nm under near-UV light of 395 nm excitation,corresponding to Eu3+ions typical transitions of 5D0→7F1 and 5D0→7F2.The optimum concentration of Eu3+ions is 9 mol％for C-LBTO:xEu3+samples and the quenching interaction type is the nearest-neighbor ion interaction.The thermal stability of the C-LBTO:0.09Eu3+sample was investigated in detail and the device application further suggests that C-LBTO:0.09Eu3+can be used as a red phosphor for near-UV excited w-LEDs in lighting.
查看更多>>摘要：Dy3+and Lu3+co-doped CaLaGa3O7 phosphors were prepared via high-temperature solid-phase reaction.The electronic structures of LuxCaLa0.98-xGa3O7 were investigated by the first-principles calculations.The influence of Lu3+on yellow light emission was studied using X-ray diffraction(XRD)and photoluminescence(PL)measurements.The XRD results indicate that compared to Dy3+∶CaLaGa3O7,the cell parameters of Dy3+∶LuCaLaGa3O7 tend to decrease,which is due to the smaller radius of Lu3+.When pumped by blue GaN laser diode(LD),the emission peaks of phosphors with different Lu3+doping concentrations in the visible region are similar,with the strongest peak at 574 nm in the yellow light region,which is sensitive to human eyes.The optimal doping concentration of Lu3+is confirmed to be 1 at％,when all emission spectra and measured fluorescence lifetimes are taken into account.Moreover,the optimal phosphor composition Dy3+∶LuxCaLa0.98-xGa3O7(x=0.01)has an internal quantum effi-ciency(IQE)of 46.94％and an external quantum efficiency(EQE)of 15.19％.Most notably,the prepared phosphor demonstrates excellent thermal stability and a high activation energy(0.203 eV).In addition,the International Illumination Commission color coordinates of the Dy3+∶LuxCaLa0.98-xGa3O7 phosphors are in the yellow light area.The above analysis indicates that the Dy3+∶LuxCaLa0.98-xGa3O7(x=0.01)phosphor has promising application prospects in yellow light-emitting devices.
查看更多>>摘要：Layered rare-earth hydroxides(LREHs)draw wide research interest because of their peculiar crystal structure,rich interlayer chemistry and abundant functionality of the RE element,but are limited to the two categories of RE2(OH)5A·nH2O(A:typical of Cl-or NO3)and RE2(OH)4SO4·nH2O.On the other hand,rare-earth oxysulfates(RE2O2SO4)have attracted attention due to their properties of large-capacity ox-ygen storage,low-temperature magnetism and luminescence,but their preparation procedure mostly involves toxic Sox gases and/or complicated procedures.In this work,RE2(OH)2CO3SO4-nH2O as a new family of LREHs(RE=Gd-Lu lanthanides and Y)were produced via hydrothermal reaction,from which phase-pure RE2O2SO4 was derived via subsequent annealing at 800 ℃ in air without the involvement of Sox.The compounds were thoroughly characterized to reveal the intrinsic influence of lanthanide contraction(RE3+radius)on crystal structure,thermal behavior(dehydroxylation/decarbonation/desulfurization),vibrational property and crystallite morphology.Through analyzing the photo-luminescence of Eu3+and Sm3+in the Gd2O2SO4 typical host it is found that the 617 nm(Eu3+,λex=275 nm)and 608 nm(Sm3+,λex=407 nm)main emissions can retain as high as-79.6％and 85.5％of their room-temperature intensities at 423 K,with activation energies of-0.19 and 0.21 eV for thermal quenching,respectively.Application also indicates that both the phosphors have the potential for optical temperature sensing via the fluorescence intensity ratio(FIR)technology,whose maximum relative sensitivity reaches～2.70％/K for Eu3+and 1.73％/K for Sm3+at 298 K.
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