Low-voltage Electron Beam Excitation Research Articles

Uniform and well-dispersed GdVO4 hierarchical architectures: hydrothermal synthesis, morphology evolution, and luminescence properties

GdVO4 nano/microcrystals with different morphologies were successfully synthesized via an efficient and facile hydrothermal process using trisodium citrate (Na3Cit) as the chelating ligand. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectra (XPS), fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and cathodoluminescence (CL) spectra were employed to characterize the samples. By tuning the reaction time, vanadium sources, and Na3Cit content, GdVO4 samples with different morphologies and sizes have been successfully synthesised. The possible formation mechanism for these diverse architectures is proposed on the basis of time-dependent experiments. Under ultraviolet (UV) and low-voltage electron beam excitation, GdVO4 : Ln3+ (Ln3+ = Eu, Dy, and Sm) phosphors show strong light emissions with different colors coming from various Ln3+ ions due to an efficient energy transfer from vanadate groups to the dopants. The ability to generate GdVO4 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 light emitting phosphors, advanced flat panel display, field emission display devices or biological labeling.

Color tuning via energy transfer in Sr3In(PO4)3:Ce3+/Tb3+/Mn2+ phosphors

Sr3In(PO4)3 (SIP):Ce3+/Tb3+/Mn2+ phosphors have been prepared via a solid state reaction process. Under UV excitation, there are three energy transfer (ET) pairs in the SIP host, i.e., Ce3+ → Tb3+, Ce3+ → Mn2+, and Tb3+ → Mn2+. Both of the ETs from Ce3+ to Tb3+ and from Ce3+ to Mn2+ in the SIP host have been demonstrated to be resonant type via a dipole–quadrupole mechanism, and the critical distance (RC) calculated by the quenching concentration method and spectral overlap method, respectively, were investigated. By the ET of Ce3+ → Tb3+, Ce3+ → Mn2+, and Tb3+ → Mn2+ the emitting colors of the studied samples could be adjusted from blue to green, from blue to orange-red, and from green to green-yellow, respectively. More importantly, under low-voltage electron beam excitation, the CL spectra of the SIP:Ce3+, Mn2+ samples cover the whole visible light region, resulting in a white light emission. Additionally, the CL properties of SIP:Ce3+/Tb3+/Mn2+ phosphors have been investigated in detail. The results reveal that the as-prepared phosphors have good CL intensity and CIE coordinate stability under electron beam bombardment. Compared with the commercial green phosphor ZnO:Zn, SIP:7% Ce3+, the 10% Tb3+ sample has a higher CL brightness. In conclusion, tunable light with high quantum yield (68%) has been obtained in SIP:Ce3+/Tb3+/Mn2+ phosphors by utilizing the principle of energy transfer and properly selecting the activator contents under UV and electron beam excitation.

LaOF : Eu3+ nanocrystals: hydrothermal synthesis, white and color-tuning emission properties

Uniform LaOF and LaOF : Eu(3+) nanocrystals of the γ-form have been successfully synthesized under mild conditions via a facile hydrothermal method followed a heat treatment of their bastnaesite-type precursor (LaCO(3)F). The synthetic details, investigations into the phase purity and the presence of the oxocarbonate anion CO(3)(2-) proven by IR measurements and EDX, as well as X-ray powder diffraction data, are given. Photoluminescence (PL) and cathodoluminescence (CL) spectra were utilized to characterize the luminescence properties of the LaCO(3)F : Eu(3+) and LaOF : Eu(3+) samples. Under ultraviolet light excitation, the LaCO(3)F : Eu(3+) precursor shows an orange emission of Eu(3+) (dominated by (5)D(0)→(7)F(1)), while the product of heat treatment, LaOF : Eu(3+), shows the characteristic emissions of Eu(3+) ((5)D(J)→(7)F(J')J, J' = 0, 1, 2, 3 transitions). Under the excitation of UV and low-voltage electron beams, the emission color (including white) of LaOF : Eu(3+) can be tuned by adjusting the doping concentration of Eu(3+). The corresponding luminescence mechanisms have been discussed in detail.

Single-phased white-emitting 12CaO·7Al2O3:Ce3+, Dy3+ phosphors with suitable electrical conductivity for field emission displays

A novel white-light-emitting phosphor, 12CaO·7Al2O3:Ce3+, Dy3+with H− encaging, was prepared by the solid-state reaction in H2 atmosphere. Upon excitation at 362 nm, the phosphor shows intense white-light emission that combines the blue and yellow emissions at 476 and 576 nm, assigned to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. A weak broad blue emission centered at 430 nm is also observed and attributed to the 5d–4f transitions of Ce3+. The photoluminescence intensity of Dy3+ increases greatly with increasing Ce3+ concentration, indicating that the effective energy transfer occurred from Ce3+ to Dy3+ in the phosphor. In particular, the phosphor can be converted to a persistent semiconductor upon ultraviolet irradiation due to the electrons released from the encaged H− ions, and the electrical conductivity is measured to be 10−2 S cm−1. The conductive phosphor exhibits excellent white-light emission (CIE coordinate of (0.324, 0.323)) under low-voltage (5 kV) electron beam excitation, suggesting that the phosphor is a potential candidate for applications in field emission displays.

Single-Composition Trichromatic White-Emitting Ca4Y6(SiO4)6O: Ce3+/Mn2+/Tb3+Phosphor: Luminescence and Energy Transfer

A series of Ca(4)Y(6)(SiO(4))(6)O (CYS): Ce(3+)/Mn(2+)/Tb(3+) oxyapatite phosphors were prepared via high-temperature solid-state reaction. Under UV excitation, there exist dual energy transfers (ET), i.e., Ce(3+)→Mn(2+) and Ce(3+)→Tb(3+) in the CYS: Ce(3+), Mn(2+), Tb(3+) system and their emitting colors can be adjusted from blue to orange-red via ET of Ce(3+)→Mn(2+) and from blue to green via ET of Ce(3+)→Tb(3+), respectively. Moreover, a wide-range-tunable white light emission with high quantum yields (13%-30%) were obtained by precisely controlling the contents of Ce(3+), Mn(2+) and Tb(3+) ions. On the other hand, the CL properties of CYS: Ce(3+), Mn(2+), Tb(3+) phosphors have been investigated in detail. The studied results indicate that the as-prepared CYS: Ce(3+), Mn(2+), Tb(3+) phosphors have good CL intensity and CIE color coordinate stability with a color-tunable emission crossing the whole white light region under low-voltage electron beam excitation. In general, the white light with varied hues has been obtained in Ce(3+), Mn(2+), and Tb(3+)-triactivated CYS phosphors by utilizing the principle of energy transfer and properly designed activator contents under UV (284, 358 nm) and low-voltage (1-5 kV) electron beam excitation, which make them as a potential single-composition trichromatic white-emitting phosphor.

Color Tuning Luminescence of Ce3+/Mn2+/Tb3+-Triactivated Mg2Y8(SiO4)6O2 via Energy Transfer: Potential Single-Phase White-Light-Emitting Phosphors

Ce3+, Mn2+, and Tb3+-activated Mg2Y8(SiO4)6O2 (MYS) oxyapatite phosphors have been prepared via solid state reaction process. The Ce3+ emission at different lattice sites in MYS host has been identified and discussed. Under UV excitation, there exist dual energy transfers (ET), that is, Ce3+ → Mn2+ and Ce3+ → Tb3+ in the MYS: Ce3+/Mn2+/Tb3+ system. The energy transfer from Ce3+ to Mn2+ in MYS: Ce3+/Mn2+ phosphors has been demonstrated to be a resonant type via a dipole–quadrupole mechanism, and the critical distance (RC) calculated by quenching concentration method and spectral overlap method are 10.5 and 9.7 Å, respectively. The emitting colors of MYS: Ce3+/Mn2+/Tb3+ samples can be adjusted from blue to orange-red via ET of Ce3+ → Mn2+ and from blue to green via ET of Ce3+ → Tb3+, respectively. More importantly, a wide-range-tunable white light emission with high quantum yields (37–47%) were obtained by precise control of the contents of Ce3+, Mn2+, and Tb3+ ions. On the other hand, the CL properties of MYS: Ce3+/Mn2+/Tb3+ phosphors have been investigated in detail. The results indicate that the as-prepared MYS: Ce3+/Mn2+/Tb3+ phosphors have good CL intensity and CIE coordinate stability with a color-tunable emission crossing the whole visible light region under low-voltage electron beam excitation. In conclusion, the white light with varied hues has been obtained in Ce3+, Mn2+ and Tb3+-activated MYS phosphors by utilizing the principle of energy transfer and properly designed activator contents as well as the select of excitation wavelength under UV and low-voltage electron beam excitation.

Patterning of Gd 2(WO 4) 3:Ln 3+ (Ln = Eu, Tb) luminescent films by microcontact printing route

Gd 2(WO 4) 3 doped with Eu 3+ or Tb 3+ thin phosphor films with dot patterns have been prepared by a combinational method of sol–gel process and microcontact printing. This process utilizes a PDMS elastomeric mold as the stamp to create heterogeneous pattern on quartz substrates firstly and then combined with a Pechini-type sol–gel process to selectively deposit the luminescent phosphors on hydrophilic regions, in which a Gd 2(WO 4) 3:Ln 3+ (Ln = Eu, Tb) precursor solutions were employed as ink. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, as well as low voltage cathodoluminescence (CL) spectra were carried out to characterize the obtained samples. Under ultraviolet excitation and low-voltage electron beams excitation, the Gd 2(WO 4) 3:Eu 3+ samples exhibit a strong red emission arising from Eu 3+ 5D 0,1,2– 7F 1,2 transitions, while the Gd 2(WO 4) 3:Tb 3+ samples show the green emission coming from the characteristic emission of Tb 3+ corresponding to 5D 4– 7F 6,5,4,3 transitions. The results show that the patterning of rare earth-doped phosphors through combining microcontact printing with a Pechini-type sol–gel route has potential for field emission displays (FEDs) applications.

Yellow-emitting NaCaPO_4:Mn^2+ phosphor for field emission displays

Yellow-emitting NaCaPO(4):Mn(2+) phosphors were prepared by the Pechini sol-gel process. Under low voltage electron beam excitation, the NaCaPO(4):Mn(2+) phosphor screen shows bright yellow emission (centering at 560 nm due to the (4)T(1)→(6)A(1) transition of Mn(2+)) with the CIE color coordinate (0.428, 0.552), which has a higher color purity than commercial yellow-emitting FED phosphor (Zn, CdS):Ag(+). The color range and chromaticity saturation may be greatly enhanced when the yellow-emitting NaCaPO(4):Mn(2+) is added as an additional phosphor of the typical tricolor FEDs phosphors, which make them have potential to improve the display quality of full-color FEDs.

Promising Zn<sub>3</sub>Ta<sub>2</sub>O<sub>8</sub>:Pr<sup>3+</sup> Red Phosphor for Low Voltage Cathodoluminescence Applications

Zn3Ta2O8 is a promising host for low voltage cathodoluminescence (CL) applications. Surface chemical stability during low voltage electron beam excitation is a prime concern for phosphors to be used in various new generation information displays. Photoluminescence (PL) and CL characteristics of the Zn3Ta2O8 host doped with Pr3+ are presented. The phosphors were synthesized via solid-state reaction route at 1100°C. Red CL or PL with a maximum at 611 nm, attributed to the 1D2-3H4 transition of the Pr3+ ion, was observed at room temperature under high energy electron (2 keV, 12 μA) or a monochromatic xenon lamp (257 nm) irradiation. Electron stimulated chemical changes on the surface of the Zn3Ta2O8:Pr3+ phosphor during an electron beam exposure from 0-350 C/cm2 was monitored using Auger electron spectroscopy. The CL exhibited only a 20% loss in the original intensity during the continuous electron beam exposure. X-ray photoelectron spectroscopy (XPS) was used to estimate the redox states of the chemical constituents and a comparison of binding energies was made with the standard Ta2O5 and ZnO compounds. A correlation between the structural configuration of Zn3Ta2O8 and the XPS data is also established.

Fabrication and Luminescence Properties of Ca2RE8(SiO4)6O2: Pb2+, Dy3+ (RE = Y, Gd) One-dimensional Phosphors by Electrospinning Method

One-dimensional Ca2RE8(SiO4)6O2: Pb2+, Dy3+ (RE = Y, Gd) nanobelts and microfibers were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and low voltage cathodoluminescence (CL) were used to characterize the resulting samples. SEM and TEM results indicated that the width and the thickness of Ca2Gd8 (SiO4)6O2: Pb2+, Dy3+ nanobelts annealed at 1000°C for 4 h were 220–250 and 90–100 nm, respectively. The diameter of the Ca2Gd8(SiO4)6O2: Pb2+, Dy3+ microfibers annealed at 1000°C for 4 h was 140–190 nm. When the samples were excited by ultraviolet (254 nm), the Pb2+ can sensitize the Gd3+ sublattice, and the energy can be efficiently transferred from Pb2+ to Dy3+ in Ca2Gd8(SiO4)6O2. Under low-voltage electron beams (4–6 kV) excitation, the Ca2RE8(SiO4)6O2: Pb2+, Dy3+ (RE = Y, Gd) samples showed strong white emission. The PL and CL intensities of Ca2Gd8(SiO4)6O2: Pb2+, Dy3+ microfibers were higher than those of Ca2Gd8(SiO4)6O2: Pb2+, Dy3+ nanobelts. The CIE chromaticity coordinates of Ca2Y8(SiO4)6O2: Pb2+, Dy3+ microfibers were x = 0.323, y = 0.333, very close to the ideal white region.

Blue and green emissions with high color purity from nanocrystalline Ca 2Gd 8Si 6O 26:Ln (Ln = Tm or Er) phosphors

Blue and green light emissive nanocrystalline Ca 2Gd 8Si 6O 26 (CGS):Tm 3+ and CGS:Er 3+ phosphors with high color purity were prepared by solvothermal reaction method. The structural and morphological properties of these phosphors were evaluated by the powder X-ray diffraction (XRD) and scanning electron microscopy, respectively. From the XRD results, Tm 3+:CGS and Er 3+:CGS phosphors had the characteristic peaks of oxyapatite in the hexagonal lattice structure. The visible luminescence properties of phosphors were obtained by ultraviolet (UV) or near-UV light and low voltage electron beam (0.5–5 kV) excitation. The photoluminescence and cathodoluminescence properties were investigated by changing the variation of Tm 3+ or Er 3+ concentrations and the acceleration voltage, respectively. The CGS:Tm 3+ phosphors exhibited the blue emission due to 1D 2→ 3F 4 transition, while the CGS:Er 3+ phosphors showed the green emission due to 4S 3/2→ 4I 15/2 transition. The color purity and chromaticity coordinates of the fabricated phosphors are comparable to or better than those of standard phosphors for lighting or imaging devices.

Investigations on the low voltage cathodoluminescence stability and surface chemical behaviour using Auger and X-ray photoelectron spectroscopy on LiSrBO 3:Sm 3+ phosphor

Orange-red emissive LiSrBO 3:Sm 3+ phosphors were synthesized through the solid-state reaction method. Under UV radiation (221 nm) and low-voltage electron beam (2 keV, 12 mA/cm 2) excitation, the Sm 3+ doped LiSrBO 3 phosphor shows emission corresponding to the characteristic 4G 5/2- 6H 7/2 transitions of Sm 3+ with the strongest emission at 601 nm. A high stability of cathodoluminescence (CL) emission during prolong electron bombardment with low-energy electrons was observed. Surface sensitive diagnostic tools such as Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used to study the surface chemistry. AES results revealed modifications in the surface concentrations of Li, Sr, B, O and C on the surface of the LiSrBO 3:Sm 3+ phosphor as indicated by the changes in their Auger peak to peak heights (APPH) as a function of electron dose. Observed changes in the high resolution XPS spectra of the LiSrBO 3:Sm 3+ surface irradiated with the low energy electron beam provide evidence of compositional and structural changes as a result of the electron beam stimulated surface chemical reactions (ESSCRs). Additional SrO 2 was identified by XPS on the phosphor surface after it received an electron dose of 300 C/cm 2 together with the increase in the concentrations of chemical species containing the B–C–O bonding. The new surface chemical species formed during electron beam bombardment are possibly responsible for the stability of the CL in the LiSrBO 3:Sm 3+ phosphor.

Red Emitting Ca2GeO4:Eu3+ Phosphors for Field Emission Displays

A novel red emitting phosphor, Eu3+-doped Ca2GeO4 was prepared through the solid state reaction. We also replace Ca2+ with Mg2+ and Ba2+ ions and add Li+, Al3+ ions as charge compensators in the Ca2GeO4 host to improve the luminescence properties of Ca2GeO4:Eu3+ phosphor. XRD, FE-SEM, photoluminescence and cathodoluminescence spectra were utilized to characterize the samples. XRD reveals that pure Ca2GeO4 phase can be obtained at 1250°C and all the above cation substitutions can be achieved in a certain concentration range except for Ba2+ ion. FE-SEM images indicate that the Ca1.99GeO4:0.01Eu3+ sample and its substitutions consist of aggregated particles with size ranging from 0.5 to 2 μm, and Ba1.99GeO4:0.01Eu3+ sample is composed of uniform and spindle-like structures with the size ranging from 300 to 500 nm. Under the excitation of ultraviolet light and low-voltage electron beams, the Ca2GeO4:Eu3+ phosphor shows the characteristic emissions of Eu3+ (5D0–7F2 at 613 nm, red). The optimum concentration for the luminescence Eu3+ is determined to be 0.01 in Ca2−xGeO4:xEu3+ phosphor. The luminescent intensity can be improved by co-doping the Mg2+ ions and charge compensators (Li+ and Al3+) to partially substitute of Ca2+ ions.

Uniform Hollow Lu2O3:Ln (Ln = Eu3+, Tb3+) Spheres: Facile Synthesis and Luminescent Properties

Uniform hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) phosphors have been successfully prepared via a urea-assisted homogeneous precipitation method using carbon spheres as templates, followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, kinetic decays, quantum yields (QY), and UV-visible diffuse reflectance spectra were employed to characterize the samples. The results show that hollow Lu(2)O(3):Ln spheres can be indexed to cubic Gd(2)O(3) phase with high purity. The as-prepared hollow Lu(2)O(3):Ln phosphors are confirmed to be uniform in shape and size with diameter of about 300 nm and shell thickness of approximate 20 nm. The possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow Lu(2)O(3):Ln microspheres has been proposed. Upon ultraviolet (UV) and low-voltage electron beams excitation, the hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) spheres exhibit bright red (Eu(3+), (5)D(0)-(7)F(2)) and green (Tb(3+), (5)D(4)-(7)F(5)) luminescence, which may find potential applications in the fields of color display and biomedicine.

Tunable luminescence of Ce3+/Mn2+-coactivated Ca2Gd8(SiO4)6O2 through energy transfer and modulation of excitation: potential single-phase white/yellow-emitting phosphors

Ce3+/Mn2+-coactivated Ca2Gd8(SiO4)6O2 (CGS) oxyapatite phosphors have been prepared via high temperature solid state reaction process. The Ce3+ emission at different lattice sites has been identified and discussed. The energy transfer from Ce3+ to Mn2+ in CGS:Ce3+/Mn2+ phosphors has been validated and demonstrated to be a resonant type via a dipole-quadrupole mechanism, and the critical distance (RC) calculated by quenching concentration method and spectral overlap method are 9.4 A and 9.2 A, respectively. A color-tunable emission in CGS:Ce3+/Mn2+ phosphors can be realized by the modulation of excitation wavelengths, namely, the change of Ce3+ emission at different lattice sites and the relative PL intensity of Ce3+ and Mn2+. In addition, the cathodoluminescence (CL) properties of CGS:Ce3+/Mn2+ phosphors including the CL spectra, 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 coordinate have been investigated in detail. The results indicate that the as-prepared CGS:Ce3+/Mn2+ phosphors have a good CL intensity stability and CIE coordinate stability with a color-tunable emission from blue to yellow, crossing the white area by the energy transfer from Ce3+ to Mn2+ under low-voltage electron beam excitation. In conclusion, the wide-ranged white light with varied hues have been obtained in Ce3+ and Mn2+ coactivated CGS phosphors by utilizing the principle of energy transfer and properly designed activator contents as well as the selection of excitation wavelength under UV (287–352 nm) and low-voltage (1–7 kV) electron beam excitation. Therefore, the CGS:Ce3+/Mn2+ phosphors may potentially be used as single-phased white/yellow-emitting phosphor for UV LEDs (light emitting diodes) and FEDs (field emission displays).

Cyan-emitting Ti4+- and Mn2+-coactivated Mg2SnO4 as a potential phosphor to enlarge the color gamut for field emission display

Under low-voltage electron beam excitation, wide range and bright cyan light emissions have been realized for the first time in the Ti4+, Mn2+-coactivated Mg2SnO4 systems, which can enlarge the color gamut of tricolor FED phosphors and thus increase the display quality of full-color FEDs.

Monodisperse Gd2O3:Ln (Ln = Eu3+, Tb3+, Dy3+, Sm3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanocrystals with tunable size and multicolor luminescent properties

Multicolor and monodisperse Gd2O3:Ln (Ln = Eu3+, Tb3+, Dy3+, Sm3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanocrystals (NCs) with narrow size distribution were prepared by a homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, and kinetic decays were employed to characterize the samples. The results show that the Gd2O3:Ln NCs can be directly indexed to cubic Gd2O3 phase with high purity. And the possible formation mechanism and the chemical reaction of each step to form spherical Gd2O3:Ln NCs are proposed according to the concerned analysis. Upon ultraviolet and low-voltage electron beams excitation, Gd2O3:Ln (Ln = Eu3+, Tb3+, Dy3+, and Sm3+) NCs exhibit respective bright red (Eu3+, 5D0 → 7F2), green (Tb3+, 5D4 → 7F5), blue (Dy3+, 4F9/2 → 6H13/2) and yellow (Sm3+, 4G5/2 → 6H7/2) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Gd2O3:Ln (Ln = Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) exhibit characteristic up-conversion (UC) emissions of Er3+, Tm3+, and Ho3+, respectively.

Morphological control and luminescence properties of lanthanide orthovanadate LnVO4(Ln = La to Lu) nano-/microcrystals viahydrothermal process

Lanthanide orthovanadate LnVO4 (Ln = La to Lu) nano-/microcrystals with multiform crystal structures (monoclinic and tetragonal) and morphologies (separated nanoparticles, micropancake, microdoughnut and spherical aggregates) were successfully synthesized by a facile, effective, and environmentally friendly hydrothermal method. X-Ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, photoluminescence spectra, low-voltage cathodoluminescence, and kinetic decays were used to characterize the samples. The experimental results indicated that the use of the organic additive trisodium citrate (Cit3−) has an obvious impact on the morphologies of the products. The possible formation mechanisms for LnVO4 nano-/microcrystals with diverse well-defined morphologies have been presented in detail. Additionally, we systematically investigate the luminescent properties of the LuVO4:Ln3+ (Ln = Eu, Sm and Dy). Due to an efficient energy transfer from vanadate groups to the dopants, LuVO4:Ln3+ (Ln = Eu, Sm and Dy) phosphors showed the strong characteristic emission of Ln3+ under ultraviolet excitation and low-voltage electron beam excitation. Furthermore, the PL emission color of LuVO4:Ln3+ (Ln = Eu, Sm and Dy) phosphors can be tuned from blue to red, orange-red, and green easily by partial replacement VO43− with PO43− and changing the doping concentrations (x) of Ln3+.

LuVO4:Ln3+ (Ln = Sm, Eu, Dy, Er and Tm) with high uniform size and morphology: Controlled synthesis, growth mechanism and optical properties

Uniform nanoerythrocyte-like, dodecahedron and spindle-like LuVO4 had been successfully synthesized on a large scale by a simple complex agent assisted hydrothermal method. The nanoerythrocyte-like LuVO4 was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, photoluminescence and cathodoluminescence. The possible formation mechanism of the LuVO4 with different morphologies were proposed. The LuVO4:Ln3+ (Ln = Sm, Eu, Dy, Er and Tm) phosphors show strong light emissions with different colors due to the different activator ions under ultraviolet light excitation or low-voltage electron beam excitation and the LuVO4:Sm3+ samples with different complex agents exhibit interesting morphology-dependent optical properties. The complex-agents-assisted hydrothermal synthesis provides us one method to explore the special morphology of nano/micromaterials and the new optical materials.

The fabrication of one-dimensional Ca 4Y 6(SiO 4) 6O: Ln 3+ (Ln = Eu, Tb) phosphors by electrospinning method and their luminescence properties

One-dimensional Ca 4Y 6(SiO 4) 6O: Ln 3+ (Ln = Eu, Tb) microfibers were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD) pattern and high-resolution transmission electron microscopy (HRTEM) confirmed that the fibers were composed of hexagonal Ca 4Y 6(SiO4) 6O phase. Thermogravimetric and differential scanning calorimetry (TG–DSC) results showed that the Ca 4Y 6(SiO4) 6O phase began to crystallize at 740 °C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated that the diameter of as-prepared microfibers ranged from 390 to 900 nm and the diameter of the microfibers annealed at 1000 °C ranged from to 120 to 260 nm. Under ultraviolet and low-voltage electron beams (3–5 kV) excitation, the Ca 4Y 6(SiO 4) 6O: Ln 3+ (Ln = Eu, Tb) samples showed the red and green emission, corresponding to 5D 0 → 7F 2 transition of Eu 3+ and 5D 4 → 7F 5 transition of Tb 3+, respectively.