Low-voltage Electron Beam Excitation Research Articles

Soft-chemical synthesis and tunable luminescence of Tb3+, Tm3+/Dy3+-doped SrY2O4 phosphors for field emission displays

Tb(3+), Tm(3+), and Dy(3+)-activated SrY2O4 phosphors have been prepared via Pechini-type sol-gel method. X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) and lifetimes, as well as cathodoluminescence (CL) spectra were used to characterize the samples. Under low-voltage electron beam excitation, the Tb(3+)-doped samples show a green luminescence, with a better CIE coordinates and higher emission intensity than the commercial product ZnO: Zn. Blue and yellow emissions could be obtained by doping with Tm(3+) and Dy(3+), respectively. A color-tunable emission in SrY2O4 phosphors can be realized by co-doping with Tm(3+) and Dy(3+). White cathodoluminescence (CL) has been realized in a single-phase SrY2O4 host by co-doping with Tm(3+) and Dy(3+) for the first time with CIE (0.315, 0.333). Furthermore, the cathodoluminescence (CL) properties of SrY2O4: Tb(3+)/Tm(3+)/Dy(3+) phosphors including the dependence of CL intensity on accelerating voltage and filament current, the decay behaviour of CL intensity under electron bombardment, and the stability of CIE chromaticity coordinate have been investigated in detail. The as-prepared phosphors might be promising for use in field-emission display (FED) devices.

Hydrothermal synthesis and improved luminescent properties of nanosheet-based rare earth orthoborates lantern-like assemblies

Hexagonal vaterite-type LuBO3:Tb3+/Eu3+ lantern-like phosphors have been successfully prepared by a simple hydrothermal process directly without sintering treatment. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, photoluminescence, low-voltage cathodoluminescence, and kinetic decays were used to characterize as-prepared phosphors, which present complex lantern-like 3D assemblies that are composed of nanosheets with thickness of about 23 nm and high crystallinity in spite of the moderate reaction temperature of 210 °C. The reaction mechanism and the self-assembly evolution process have been proposed. The pH, temperature, time, and ethylene glycol play critical roles in the formation of this specific hierarchical and complex 3D structure. Under UV excitation and low-voltage electron beam excitation, vaterite-type LuBO3:Tb3+ samples showed the characteristic green emission of Tb3+ corresponding to 5 D 4 → 7 F 5 transitions; vaterite-type LuBO3:Eu3+ particles exhibited a strong red emission corresponding to primary group electric dipole transition 5 D 0 → 7 F 2 with much higher R/O values (chromatically redder fluorescence, increase of 29 %) compared with samples by conventional solid-state reaction, which have potential applications in fluorescent lamps and field emission displays.

Shape Controllable Synthesis and Luminescence Properties of LuVO4:Ln3+ (Ln3+ = Eu, Sm, and Dy) Nano/Microstructure

The LuVO4:Ln3+ (Ln3+ = Eu, Dy, and Sm) nano/microcrystals with different shapes were synthesized through a simple hydrothermal route assisted by trisodium citrate (Na3Cit). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL) spectra were employed to characterize the samples. A series of controlled experiments indicate that the shape and size of as-prepared architectures can be tuned effectively by controlling the reaction conditions, such as vanadium sources, different organic additives, the content of organic additive trisodium citrate (Cit(3-)), and reaction time. It is found that Cit(3-) as a ligand and shape modifier has the dynamic effect by adjusting the growth rate of different facets under different experimental conditions, resulting in the formation of various geometries of the final products. The possible formation mechanisms for products with diverse architectures have been presented in detail. The Ln3+ ions doped LuVO4 sample exhibit respective bright red, orange and green-yellow luminescence of Eu3+, Sm3+, and Dy3+ under ultraviolet excitation and low-voltage electron beam excitation. The ability to generate LuVO4 nano/microstructures with diverse shapes, and multicolor emission provides a great opportunity for systematically evaluating their luminescence properties, as well as fully exploring their applications in many types of color display fields.

Cathodoluminescence properties of Tb3+-doped Na3YSi2O7 phosphors

Tb3+-doped Na3YSi2O7 phosphors were prepared by the sol–gel method and then characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy, and cathodoluminescence spectroscopy. The XRD results reveal that the Tb3+ ions have been introduced as dopants into the Na3YSi2O7 host lattice. Under low-voltage electron beam excitation, the phosphors exhibit the characteristic emissions of Tb3+ (5D3,4→7FJ, J=3–6 transitions). The luminescence color of the phosphors can be tuned from greenish-blue to bluish-green and to green by controlling the Tb3+ concentration within the 0.0005–0.15 (x value). The optimum Tb3+ doping concentration is 10 mol%, and the “dead voltage” is approximately 1.35 kV. All results indicate that the sample is a phosphor candidate for field-emission displays.

Hydrothermal Derived LaOF:Ln3+ (Ln = Eu, Tb, Sm, Dy, Tm, and/or Ho) Nanocrystals with Multicolor-Tunable Emission Properties

A series of LaOF:Ln(3+) (Ln = Eu, Tb, Sm, Dy, Tm, and/or Ho) nanocrystals with good dispersion have been successfully prepared by the hydrothermal method followed a heat-treatment process. Under ultraviolet radiation and low-voltage electron beam excitation, the LaOF:Ln(3+) nanocrystals show the characteristic f-f emissions of Ln(3+) (Ln = Eu, Tb, Sm, Dy, Tm, or Ho) and give red, blue-green, orange, yellow, blue, and green emission, respectively. Moreover, there exists simultaneous luminescence of Tb(3+), Eu(3+), Sm(3+), Dy(3+), Tm(3+), or Ho(3+) individually when codoping them in the single-phase LaOF host (for example, LaOF:Tb(3+), Eu(3+)/Sm(3+); LaOF:Tm(3+), Dy(3+)/Ho(3+); LaOF:Tm(3+), Ho(3+), Eu(3+) systems), which is beneficial to tune the emission colors. Under low-voltage electron beam excitation, a variety of colors can be efficiently adjusted by varying the doping ions and the doping concentration, making these materials have potential applications in field-emission display devices. More importantly, the energy transfer from Tm(3+) to Ho(3+) in the LaOF:Tm(3+), Ho(3+) samples under UV excitation was first investigated and has been demonstrated to be a resonant type via a quadrupole-quadrupole mechanism. The critical distance (R(Tm-Ho)) is calculated to be 28.4 Å. In addition, the LaOF:Tb(3+) and LaOF:Tm(3+) phosphors exhibit green and blue luminescence with better chromaticity coordinates, color purity, and higher intensity compared with the commercial green phosphor ZnO:Zn and blue phosphor Y(2)SiO(5):Ce(3+) to some extent under low-voltage electron beam excitation.

Electrospinning synthesis and luminescent properties of one-dimensional Ca2Gd8(SiO4)6O2:Eu3+ microfibers and microbelts

One-dimensional Ca2Gd8(SiO4)6O2:Eu3+ microfibers and microbelts were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), cathodoluminescence (CL) and decay kinetics were used to characterize the resulting samples. The diameters of the Ca2Gd8(SiO4)6O2:Eu3+ microfibers annealed at 1000 °C were in the range of 130–210 nm. The width and the thickness of Ca2Gd8(SiO4)6O2:Eu3+ microbelts annealed at 1000 °C were in the range of 290–500 nm and 110–160 nm, respectively. When the samples were excited by ultraviolet (275 nm), intense red emission from Eu3+ ions was observed. The charge transfer band of microbelts was broader than microfibers and the peak of charge transfer band moved to lower energy area. Under low-voltage electron beams (3–5 kV) excitation, the Ca2Gd8(SiO4)6O2:Eu3+ microfibers also showed strong red emission.

Large-scale synthesis of Lu2O3:Ln3+ (Ln3+ = Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) microspheres and their photoluminescence properties

In this work, multicolor and monodisperse Lu2O3:Ln3+ (Ln3+=Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and cathodoluminescence (CL) spectra were employed to characterize the samples. Upon ultraviolet and low-voltage electron beams excitation, Lu2O3:Ln3+ (Ln3+=Eu3+ and Tb3+) samples exhibit respective bright red (Eu3+, 5D0→7F2) and green (Tb3+, 5D4→7F5) down-conversion (DC) emissions. Under 980nm NIR irradiation, Lu2O3:Ln3+ (Ln3+=Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) exhibit characteristic up-conversion (UC) emissions of green (Er3+, 4S3/2, 2H11/2→4I15/2), blue (Tm3+, 1G4→3H6) and yellow-green (Ho3+, 5F4, 5S2→5I8), respectively. These finding may find potential applications in bioanalysis, optoelectronic and nanoscale devices, field emission displays, and so on.

Monodisperse and core-shell structured SiO2@Lu2O3:Ln3+ (Ln=Eu, Tb, Dy, Sm, Er, Ho, and Tm) spherical particles: A facile synthesis and luminescent properties

The core-shell structured SiO2@Lu2O3:Ln3+ particles were realized by coating the Lu2O3:Ln3+ phosphors onto the surface of non-aggregated, monodisperse and spherical SiO2 particles by the Pechini sol–gel method. The as-synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray (EDX) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photolumiminescence (PL), and low-voltage cathodoluminescence (CL). The results indicate that the 800°C annealed sample consists of crystalline Lu2O3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. The as-obtained particles show strong light emission with different colors corresponding to different Ln3+ ions under ultraviolet–visible light excitation and low-voltage electron beams excitation, which have potential applications in fluorescent lamps and field emission displays.

Yellow-white emission of Ce^3+ and Eu^2+ doped Li_2SrSiO_4 under low-voltage electron-beam excitation

Ce(3+) and Eu(2+) activated Li(2)SrSiO(4) phosphors were prepared using a high temperature solid-state reaction technique. The VUV-UV-vis photoluminescence (PL) of Ce(3+)-doped phosphors Li(2-x)Sr(1-x)Ce(x)SiO(4) and Eu(2+)-doped phosphors Li(2)Sr(1-x)Eu(x)SiO(4), the low-voltage cathodoluminescence (CL) of Eu(2+)-doped phosphor Li(2)Sr(0.991-x)Eu(0.009)SiO(4) and Ce(3+)-Eu(2+) co-doped phosphors Li(2-x)Sr(0.991-x)Eu(0.009)Ce(x)SiO(4) were measured and discussed in consideration of their potential application in field emission displays (FEDs). The intense emission of phosphors Li(2-x)Sr(0.991-x)Eu(0.009)Ce(x)SiO(4) is tunable in yellow to white color gamut under low-voltage cathode ray excitation.

Fabrication and luminescence properties of one-dimensional ZnAl2O4 and ZnAl2O4: A3+ (A = Cr, Eu, Tb) microfibers by electrospinning method

One-dimensional ZnAl2O4 and ZnAl2O4: A3+ (A=Cr, Eu, Tb) microfibers were fabricated by electrospinning method. X-ray diffraction pattern confirmed that the fibers were composed of the cubic ZnAl2O4 phase. Scanning electron microscopy and transmission electron microscopy results indicated that the ZnAl2O4 microfibers annealed at 1000°C were composed of some smaller nanoparticles and the diameters of the microfibers were in the range of 140–230nm. Under the excitation of ultraviolet and low-voltage electron beams (3–5kV), the ZnAl2O4: A3+ (A=Cr, Eu, Tb) samples showed the emission of the host and the doping ions. The evolution of the optical properties of microfibers with increasing the doping concentration was investigated in detail. Green and red emissions can be realized in ZnAl2O4 microfibers by changing the doping ions. The ZnAl2O4: A3+ (A=Cr, Eu, Tb) microfibers have potential applications in full-color field emission displays.

Intensive green emission of ZnAl_2O_4:Mn^2+under vacuum ultraviolet and low-voltage cathode ray excitation

A series of Zn(1-x)Mn(x)Al(2)O(4) (x=0.001∼0.08) phosphors were synthesized by a traditional solid-state reaction route. Their photoluminescence under vacuum ultraviolet (VUV, energy E>50000 cm(-1), wavelength λ<200 nm) and cathodoluminescence under low-voltage electron beam excitation were evaluated. The luminescence decays were also measured. The intense green emission was observed with a peak at about 510 nm upon 172/147 nm excitation. The luminescence of optimum phosphor Zn(0.99)Mn(0.01)Al(2)O(4) (ZAM) was compared with that of commercial green phosphor Zn(2)SiO(4):Mn(2+) (ZSM). The maximum emission intensity of ZAM is larger than that of ZSM under 172/147 nm and low-voltage electron beam excitation. The values of chromaticity coordinates reveal the phosphors can evidently enlarge the tricolor gamut. The results show that the ZnAl(2)O(4):Mn(2+) phosphors may be considered as candidates for Hg-free lamps, plasma flat backlights, and field emission backlights for liquid crystal displays.

Synthesis and characterization of Zn2GeO4:Mn2+ phosphor for field emission displays

Zn2−2x Mn2x GeO4 (x=0, 0.001, 0.01) phosphors were prepared by conventional solid state reaction technique. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), diffuse reflection spectra, photoluminescence (PL), and cathodoluminescence (CL) spectroscopy were utilized to characterize the synthesized phosphors. The Mn2+-activated Zn2GeO4 phosphors exhibit narrow emission band at 532 nm under the excitation of ultraviolet light, which due to the 4T1(4G)–6A1(6S) transition of Mn2+ ions. Also it is observed that there exists energy transfer between the Zn2GeO4 host lattice and the activator (Mn2+). Under excitation of low-voltage electron beams, Zn2GeO4:Mn2+ shows strong green emission band dominating at 535 nm, corresponding to the 4T1(4G)–6A1(6S) emission of Mn2+ ions. The emission intensity and chromaticity coordinates of Zn2GeO4:Mn2+ as a function of accelerating voltage and the filament current were also investigated.

Electrospinning synthesis and luminescence properties of one-dimensional La9.33(SiO4)6O2: Ln3+ (Ln = Ce, Eu, Tb) microfibers

One-dimensional La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and low voltage cathodoluminescence (CL) as well as kinetic decay were used to characterize the resulting samples. SEM and TEM results indicated that the diameter of the microfibers annealed at 1000 °C for 3 h was 200-245 nm. The microfibers were further composed of fine and closely linked nanoparticles. La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors showed the characteristic emission of Ce(3+) (5d → 4f), Eu(3+) ((5)D(0)→(7)F(J)) and Tb(3+) ((5)D(3,4)→(7)F(J)) under ultraviolet excitation and low-voltage electron beams (3-5 kV) excitation. An energy transfer from Ce(3+) to Tb(3+) was observed in the La(9.33)(SiO(4))(6)O(2): Ce(3+), Tb(3+) phosphor under ultraviolet excitation and low-voltage electron beam excitation. Luminescence mechanisms were proposed to explain the observed phenomena. Blue, red and green emission can be realized in La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers by changing the doping ions. So the La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors have potential applications in full-color field emission displays.

Tunable luminescence and energy transfer properties in KCaGd(PO4)2:Ln3+/Mn2+ (Ln = Tb, Dy, Eu, Tm; Ce, Tb/Dy) phosphors with high quantum efficiencies

Photoluminescence (PL) and cathodoluminescence (CL) properties of Ln3+ (Ln = Tb, Dy, Eu, Tm, Ce) and Mn2+-activated KCaGd(PO4)2 (KCG) phosphors were investigated. Under UV excitation, KCG:Tb3+, KCG:Dy3+, KCG:Eu3+, KCG:Tm3+, and KCG:Mn2+ samples exhibit the characteristic emission of the activators, respectively. By altering doping activators and adjusting their relative doping concentrations in the KCG host, we obtained white emission in KCG:Tm3+, Tb3+, Eu3+, KCG:Tb3+, Mn2+, Eu3+, KCG:Tb3+, Eu3+, and KCG:Dy3+, Eu3+ samples under the excitation of 275 or 356 nm UV. Besides, there exist three energy transfer pairs in the KCG host, i.e., Ce3+ → Tb3+, Ce3+ → Dy3+, and Ce3+ → Mn2+. Upon excitation at 280 nm, the absolute quantum yield of the optimized KCG:Ce3+, Tb3+ is 90.6%. Under the low-voltage electron beam excitation, the CL properties of KCG:Ln3+/Mn2+ phosphors have been investigated in detail, and a variety of colors can be obtained in these samples. All of the results of this study reveal that the as-prepared KCG:Ln3+/Mn2+ phosphors have good luminescent intensity under UV and the low-voltage electron beam excitation, especially KCG:Ce3+, Tb3+ samples, making these materials have potential applications in white-light LEDs and field emission display devices.

Nanocrystalline CaYAlO4:Tb3+/Eu3+ as promising phosphors for full-color field emission displays

Eu(3+) and/or Tb(3+)-doped CaYAlO(4) phosphor samples were synthesized by Pechini-type sol-gel method. X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and cathodoluminescence (CL) spectra were used to characterize the samples. For CaYAlO(4):Tb(3+), it is shown that the Tb(3+)-doping concentration has a significant effect on the (5)D(3)/(5)D(4) emission intensity of Tb(3+), which is attributed to the cross relaxation from (5)D(3) to (5)D(4). Under the 4f(8)→ 4f(7)5d excitation of Tb(3+) or low-voltage electron beams excitation, the CaYAlO(4):Tb(3+) phosphors show tunable luminescence from blue to cyan, and then to green with the change of Tb(3+)-doping concentration. The CaYAlO(4):Eu(3+) samples exhibit a reddish-orange emission of Eu(3+) corresponding to (5)D(0,1)→(7)F(0,1,2,3) transitions. Furthermore, a white emission can be realized in the single phase CaYAlO(4) host by reasonably adjusting the doping concentrations of Tb(3+) and Eu(3+) under low-voltage electron beams excitation. Compared with the commercial blue (Y(2)SiO(5):Ce(3+)) and green (ZnO:Zn) phosphors, CaYAlO(4):0.1%Tb(3+) and CaYAlO(4):5%Tb(3+) phosphors have higher CL intensity and stability under continuous electron bombardment. Due to the excellent CL properties and good CIE chromaticity coordinates, the as-prepared Tb(3+)/Eu(3+)-doped CaYAlO(4) nanocrystalline phosphors have potential application in FEDs devices.

Luminescence and energy transfer properties of Ca8Gd2(PO4)6O2:A (A = Ce3+/Eu2+/Tb3+/Dy3+/Mn2+) phosphors

A series of Ca8Gd2(PO4)6O2, (CGPO):A (A = Ce3+, Eu2+, Tb3+, Dy3+, Mn2+, and their combination), phosphors with the oxyapatite structure have been prepared via a Pechini-type sol–gel process. X-ray diffraction (XRD), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, absolute quantum yield and lifetimes were utilized to characterize the samples. Under UV and low voltage electron beam excitation, the Ce3+ ion, as a sensitizer, can transfer its energy to other activators (Eu2+, Tb3+, Dy3+, and Mn2+) in the CGPO:Ce3+, Eu2+/Tb3+/Dy3+/Mn2+ system. The energy transfer from Ce3+ to Eu2+ and Tb3+ has been demonstrated to be a resonant type, via a dipole–dipole and dipole–quadrupole mechanism, respectively, and the critical distances are calculated to be 28.70 and 12.60 A, respectively. The absolute quantum yields of the Ce3+ and Eu2+ coactivated CGPO phosphors are enhanced with respect to those of the Eu2+ singly activated samples via energy transfer. Under the excitation of a low voltage electron beam, the emitting colors of CGPO:Ce3+/Tb3+/Dy3+/Mn2+ samples can be adjusted from blue to green, and from blue to white to yellow-green by control of the contents of Ce3+, Tb3+, Dy3+, and Mn2+. The CL properties have been investigated in detail, and the results indicate that the as-prepared Ca8Gd2(PO4)6O2:A (A = Ce3+/Eu2+/Tb3+/Dy3+/Mn2+) samples have good CL intensity and CIE coordinate stability with a wide color-tunable emission. Based on the good PL and CL properties and the varied hues of the CGPO host by adjusting the concentration of the activators (Ce3+/Eu2+/Tb3+/Dy3+/Mn2+), CGPO might be promising as a host material for use in solid-state lighting and display fields.

General and facile method to fabricate uniform Y2O3:Ln3+ (Ln3+ = Eu3+, Tb3+) hollow microspheres using polystyrene spheres as templates

Well-dispersed, uniform Y2O3:Ln3+ (Ln3+ = Eu3+, Tb3+) hollow microspheres have been successfully prepared via a urea-assisted homogeneous precipitation method using polystyrene (PS) as templates, followed by a subsequent calcination process. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), photoluminescence (PL) spectra, and cathodoluminescence (CL) spectra were employed to characterize the samples. The results demonstrate that the samples can be well indexed to the pure cubic phase of Y2O3. The TEM and SEM images indicate that the shell of the uniform hollow spheres, whose diameter is about 2.1 μm, is composed of many uniform nanoparticles with diameters of around 20 nm. Upon ultraviolet (UV) and low-voltage electron beam excitation, the Y2O3:Ln3+ (Ln3+ = Eu3+, Tb3+) samples exhibit bright red (Eu3+, 5D0 → 7F2), and green (Tb3+, 5D4 → 7F5) luminescence. This material may find potential applications in light display systems, optoelectronic devices and drug delivery based on the uniform hollow structure, dimensions, and luminescence properties. Furthermore, this synthesis route may be of great significance in the preparation of other hollow spherical materials.

Self-assembled growth of LuVO4 nanoleaves: hydrothermal synthesis, morphology evolution, and luminescence properties

In the present paper, LuVO4 nanoleaves have been synthesized via a facile and low-cost complexant-assisted hydrothermal approach. The phases, morphologies, sizes, and luminescence properties of the as-prepared products were well characterized by means of XRD, FT-IR, SEM, TEM, SAED, EDX, HRTEM, PL, and CL. The results indicate that the phase, morphology, and size of the LuVO4 samples can be tuned in a controlled manner by altering the amount of Na2tar, the pH value of the initial solution, and the reaction time. The crystal growth was thoroughly investigated, and a possible formation mechanism was proposed. Upon UV and low-voltage electron beam excitation, the LuVO4:Ln3+ (Ln3+ = Eu3+, Dy3+, Sm3+, Er3+) samples exhibit bright red (Eu3+, 5D0 → 7F2), green-yellow (Dy3+, 4F9/2 → 6H13/2), orange-red (Sm3+, 4G5/2 → 6H7/2) and green (Er3+, 4S3/2 → 4I15/2) luminescence. Furthermore, the UC luminescence properties, as well as the emission mechanisms of LuVO4:Yb3+/Ln3+ (Ln3+ = Er3+, Tm3+, Ho3+) samples, were systematically investigated, which show respective green (Er3+, 4S3/2, 2H11/2 → 4I15/2), blue (Tm3+, 1G4 → 3H6) and red (Ho3+, 5F5 → 5I8) luminescence under 980 nm NIR excitation. These merits of multicolor emissions in the visible region endow this kind of material with potential applications in the field of light display systems, lasers, and optoelectronic devices.

Luminescence properties of Mn2+-doped Li2ZnGeO4 as an efficient green phosphor for field-emission displays with high color purity

Green emitting Li(2)ZnGeO(4):Mn(2+) phosphors were synthesized through a high temperature solid-state reaction process. X-Ray diffraction, field emission scanning electron microscopy, photoluminescence (PL) and cathodoluminescence (CL) spectra were utilized to characterize the synthesized samples. Under UV and electron-beam excitation, the pure Li(2)ZnGeO(4) sample shows a blue emission due to defects, while the Li(2)ZnGeO(4):Mn(2+) sample exhibits a green emission corresponding to the characteristic transition of Mn(2+) ((4)T(1)→(6)A(1)). In particular, the CL intensity (brightness) of Li(2)ZnGeO(4):Mn(2+) is higher than that of commercial green phosphor ZnO:Zn. In addition, the CL properties of Li(2)ZnGeO(4):Mn(2+) phosphor, the dependence of CL intensity on accelerating voltage and filament current, the decay behavior of CL intensity under electron bombardment, and the stability of CIE chromaticity coordinates, have been investigated in detail. The results indicate that the as-prepared Li(2)ZnGeO(4):Mn(2+) phosphor has a good CL intensity and CIE coordinate stability with green emission under low-voltage electron beam excitation. Therefore, Li(2)ZnGeO(4):Mn(2+) is a promising green phosphor for application in full-color field-emission displays.

Self-Assembled Columnar Structure Gd2O3:Eu3+: Solvothermal Synthesis and Luminescence Properties

Gadolinium oxides with self-assembled columnar morphology were successfully synthesized via a facile solvothermal method followed by a subsequent heat treatment. X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), photoluminescence spectra (PL) and energy-dispersive X-ray spectra (EDX) were used to characterize the as-obtained samples. SEM images showed that the self-assembled columnar sample entirely consisted of uniform nano-rods with diameters of about 100 nm and lengths of 200–300 nm. The Gd2O3 precursor could transform to Gd2O3 with their original morphology and slight shrinkage in the size after calcined process. XRD analysis showed that the sample was formed cubic crystal after heat-treatment. The as-obtained columnar structure Gd2O3:Eu3+ product exhibited a strong red emission corresponding to the 5D0-7F2 transition (612 nm) of Eu3+ ions under ultraviolet excitation light or low-voltage electron beam excitation, so it have finded potential applications in some fields.