Photoluminescent properties of CeF3:Tb3+ nanodiskettes prepared by hydrothermal microemulsion

In this paper, CeF₃:Tb³⁺ nanodiskettes were prepared by the hydrothermal microemulsion method for the first time and the photoluminescent properties of CeF₃:Tb³⁺ nanodiskettes were investigated. The structural properties of CeF₃:Tb³⁺ nanodiskettes were characterized by X-ray diffractions and transmission electron microscopy. The photoluminescent properties of CeF₃:Tb³⁺ with different Tb³⁺ ions concentration were investigated by excitation spectra, emission spectra and lifetime measurement. The energy transfer processes from Ce³⁺ to Tb³⁺ and from Tb³⁺ to Tb³⁺ were analyzed and discussed. Results show that CeF₃:Tb³⁺ nanodiskettes may be applied as phosphors for high resolution displaying. PACS 78.55; 78.66; 79.60     

Green light emission by Ce3+ and Tb3+ co-doped Sr3MgSi2O8 phosphors for potential application in ultraviolet whitelight-emitting diodes

Sr₃MgSi₂O₈:Ce³⁺, Tb³⁺ phosphor samples were prepared using a solid-state reaction technique, and the photoluminescence properties and energy transfer were investigated. Effective energy transfer occurred in Ce³⁺/Tb³⁺ co-doped Sr₃MgSi₂O₈ phosphors. Co-doping of Ce³⁺ was found to enhance the emission intensity of Tb³⁺ to a certain extent by transferring energy to Tb³⁺. The Ce³⁺/Tb³⁺ energy transfer was thoroughly investigated through its emission/excitation spectra and photoluminescence decay behavior. The color emitted by Sr₃MgSi₂O₈:Ce³⁺, Tb³⁺ phosphors varied from blue to green and can be controlled by altering the concentration ratio of Ce³⁺ to Tb³⁺. These results indicate that Sr₃MgSi₂O₈:Ce³⁺, Tb³⁺ may be useful as a green-emitting phosphor for ultraviolet whitelight-emitting diodes.     

Luminescence properties and energy transfer investigations of BaAl2B2O7:Ce3+,Tb3+ phosphors

Ce³⁺ and Tb³⁺ co-doped BaAl₂B₂O₇ phosphors were synthesized by the solid-state method. X-ray diffraction (XRD) was used to characterize the phase structure. The photoluminescent properties of Ce³⁺ and Tb³⁺ co-doped BaAl₂B₂O₇ phosphors were investigated by using the photoluminescence emission and excitation spectra. Under the excitation of near ultraviolet (n-UV) light, BaAl₂B₂O₇:Ce³⁺,Tb³⁺ phosphors exhibited blue emission corresponding to the f–d transition of Ce³⁺ ions and green emission bands corresponding to the f–f transition of Tb³⁺ ions, respectively. Effective energy transfer occurred from Ce³⁺ to Tb³⁺ in BaAl₂B₂O₇ host due to the observed spectra overlap between the emission spectrum of Ce³⁺ ion and the excitation spectrum of Tb³⁺ ion. The energy transfer efficiency from Ce³⁺ ion to Tb³⁺ ion was also calculated to be 71%. Furthermore, the concentration quenching and critical distance of BaAl₂B₂O₇:Ce³⁺,Tb³⁺ phosphors were also discussed. The energy transfer from Ce³⁺ to Tb³⁺ in BaAl₂B₂O₇ host was demonstrated to be resonant type via a dipole–dipole interaction mechanism with the energy transfer critical distance of 16.13 Å.     

Enhanced luminescence and degradation of SiO2:Ce,Tb powder phosphors prepared by a sol-gel process

Enhanced green photoluminescence and cathodoluminescence (CL) from Tb³⁺ ions due to co-doping with Ce³⁺ ions were observed from SiO₂:Ce,Tb powder phosphors prepared by a sol-gel technique. Blue emission from the Ce³⁺ ions was completely suppressed by Tb co-doping, presumably due to energy transfer from Ce³⁺ to Tb³⁺. In addition, the green CL intensity from SiO₂:Ce,Tb degraded by ∼50% when the powders were irradiated for 10 h with a 2 keV, 54 mA/cm² beam of electrons in an ultra-high vacuum chamber containing either 1×10⁻⁸ or 1×10⁻⁷ Torr O₂. Desorption of oxygen from the surface was observed during the decrease of CL intensity. The mechanisms for energy transfer from Ce³⁺ ions to Tb³⁺ ions to enhance the green luminescence, and mechanisms for desorption of oxygen from the phosphor surface that would result in decreased CL intensity are discussed.     

Eu/Tb ions co-doped white light luminescence Y2O3 phosphors

Y₂O₃:Eu³⁺, Tb³⁺ phosphors with white emission are prepared with different doping concentration of Eu³⁺ and Tb³⁺ ions and synthesizing temperatures from 750 to 950 °C by the co-precipitation method. The resulted phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The results of XRD indicate that the crystallinity of the synthesized samples increases with enhancing the firing temperature. The photoluminescence spectra indicate the Eu³⁺ and Tb³⁺ co-doped Y₂O₃ phosphors show five main emission peaks: three at 590, 611 and 629 nm originate from Eu³⁺ and two at 481 and 541 nm originate from Tb³⁺, under excitation of 250-320 nm irradition. The white light luminescence color could be changed by varying the excitation wavelength. Different concentrations of Eu³⁺ and Tb³⁺ ions were induced into the Y₂O₃ lattice and the energy transfer from Tb³⁺→Eu³⁺ ions in these phosphors was found. The Commission International de l’Eclairage (CIE) chromaticity shows that the Y₂O₃:Eu³⁺, Tb³⁺ phosphors can obtain an intense white emission.     

The energy transfer from Eu2+ to Tb3+ in calcium chlorapatite phosphor and its potential application in LEDs

Energy transfer from Eu²⁺ to Tb³⁺ was observed by investigating the optical properties from photoluminescence spectra and decay time curves in Tb³⁺ singly doped and Eu²⁺–Tb³⁺ co-doped calcium chlorapatite, Ca₅(PO₄)₃Cl (CPCl). It is dominated by the cooperation of a phonon-assisted energy transfer process and a non-radiative resonant energy transfer process caused by the exchange interaction. Eu²⁺–Tb³⁺ co-doped calcium chlorapatite phosphors in which Tb³⁺ can be efficiently excited by 400 nm are potential candidates for phosphor-converted LED.     

Synthesis and characterization of monodisperse spherical core-shell structured SiO2@Y3Al5O12:Ce3+/Tb3+ phosphors for field emission displays

Nanocrystalline Y₃Al₅O₁₂: Ce³⁺/Tb³⁺ (average crystalline size 30 nm) phosphor layers were coated on non-aggregated, monodisperse and spherical SiO₂ particles by the sol-gel method, resulting in the formation of core-shell structured SiO₂@Y₃Al₅O₁₂:Ce³⁺/Tb³⁺ particles. X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, photoluminescence, cathodoluminescence spectra, as well as lifetimes were utilized to characterize the core-shell structured SiO₂@Y₃Al₅O₁₂:Ce³⁺/Tb³⁺ phosphor particles. The obtained core-shell structured phosphors consist of well-dispersed submicron spherical particles with a narrow size distribution. The thickness of the Y₃Al₅O₁₂:Ce³⁺/Tb³⁺ shells on the SiO₂ cores (average size about 500 nm, crystalline size about 30 nm) could be easily tailored by varying the number of deposition cycles (100 nm for four deposition cycles). Under the excitation of ultraviolet and low-voltage electron beams (1–3 kV), the core-shell SiO₂@Y₃Al₅O₁₂:Ce³⁺/Tb³⁺ particles show strong yellow-green and green emission corresponding to the 5d–4f emission of Ce³⁺ and ⁵D₄–⁷F _J (J = 6, 5, 4, 3) emission of Tb³⁺, respectively. These phosphors may have potential application in field emission displays.     

Luminescence properties and energy transfer in Ba2Y(BO3)2Cl:Ce3+,Tb3+ phosphors

Novel green-emitting Ba₂Y(BO₃)₂Cl:Ce³⁺,Tb³⁺ phosphors were synthesized by a solid-state method. X-ray diffraction and photoluminescence spectra were utilized to characterize the structures and luminescence properties of the as-synthesized phosphors, respectively. Ba₂Y(BO₃)₂Cl:Ce³⁺,Tb³⁺ phosphors exhibit blue and green emission bands under the excitation of near-ultraviolet light. An asymmetric blue emission originates from the Ce³⁺ ion, whereas the green emission originates from the Tb³⁺ ion. A spectral overlap is found between the emission band of the Ce³⁺ ion and the excitation band of the Tb³⁺ ion, which supports the occurrence of the energy transfer from the Ce³⁺ ion to the Tb³⁺ ion. Meanwhile, the energy transfer is thoroughly investigated by their photoluminescence decay behaviors. The energy-transfer efficiency from the Ce³⁺ ion to the Tb³⁺ ion is also calculated, and a possible mechanism is proposed.     

Fabrication and luminescence properties of Al2O3:Tb3+ microspheres via a microwave solvothermal route

Al₂O₃:Tb³⁺ green phosphors were synthesized via a microwave solvothermal and thermal decomposition route, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra, and decay curves. XRD results indicate that Tb³⁺ doped samples are γ-Al₂O₃ after being calcined at 773 K. SEM results show that the particles of Al₂O₃:Tb³⁺ are hierarchically nanostructured microspheres assembled from nanosheets. The PL spectra indicate that the ⁵D₄→⁷F₅ (545 nm) electric dipole transition is the most intensive when excited at 235 nm. It is shown that 0.7 mol% of doping concentration of Tb³⁺ ions in γ-Al₂O₃:Tb³⁺ is optimum. According to Dexter's theory, the critical distance between Tb³⁺ ions for energy transfer was determined to be 18.4 Å. It is found that the curve followed the single-exponential decay. The excellent chromaticity coordinates of Al₂O₃:Tb³⁺ phosphors, as defined by the International Commission on Illumination (CIE), indicate that it is a good candidate for use in light display systems and optoelectronic devices.     

Photoluminescence and efficient energy transfer from Ce3+ to Tb3+ or Mn2+ in Ca9ZnLi(PO4)7 host

Structural and spectroscopic characterizations of the Ce³⁺/Tb³⁺(Mn²⁺) solely and Ce³⁺–Tb³⁺(Mn²⁺) doubly doped phosphate compound Ca₉ZnLi(PO₄)₇ with β-Ca₃(PO₄)₂ structure have been performed by powder X-ray diffraction and photoluminescence spectra measurements. The weak green emission from Tb³⁺ and red emission from Mn²⁺ are significantly enhanced by introduction of sensitizer Ce³⁺ ions due to an efficient resonant-type energy transfer from Ce³⁺ to activators Tb³⁺ or Mn²⁺. The energy transfer efficiency and the mechanism have been estimated based on spectroscopic data. Meanwhile, the critical distances for energy transfer between the Ce³⁺ and Tb³⁺ or Mn²⁺ ions are also calculated by the method of spectral overlapping.     

Multiplication of electronic excitations in nanophosphors Lu2O3:Eu and Lu2O3:Tb

Luminescence properties of Lu₂O₃:Eu³⁺ and Lu₂O₃:Tb³⁺ nanocrystalline powders with the particle size varying from 46 to 6 nm were studied under excitation by synchrotron radiation in the photon energy range (up to ∼22.5 eV) covering the region where the processes of multiplication of electronic excitation occur. It was found that the excitation spectra of Tb³⁺ emission from all Lu₂O₃:Tb³⁺ nanopowders have similar behavior, whereas the shape of the excitation spectra of Eu³⁺ emission from Lu₂O₃:Eu³⁺ nanopowders strongly depends on the particle size. The difference in the behavior of Lu₂O₃:Eu³⁺ and Lu₂O₃:Tb³⁺ nanophosphor systems was explained by different mechanisms of the energy transfer from the host to Eu³⁺ or Tb³⁺ ions (either the hole or electron recombination mechanism, respectively), which are differently influenced by losses of electronic excitations near the particle surface.     

Ca8Mg(SiO4)4Cl2:Ce3+, Tb3+: A potential single-phased phosphor for white-light-emitting diodes

A single-phased white-light-emitting phosphor Ca₈Mg(SiO₄)₄Cl₂:Ce³⁺, Tb³⁺ (CMSC:Ce³⁺, Tb³⁺) is synthesized by a high temperature solid-state reaction method, and its photoluminescence properties are investigated. The obtained phosphor exhibits a strong excitation band between 250 and 410 nm, matching well with the dominant emission band of a UV light-emitting-diode (LED) chip. Energy transfer from Ce³⁺ to Tb³⁺ ions has been investigated and demonstrated to be a resonant type via a dipole–dipole mechanism. The energy transfer efficiency as well as the critical distance is also estimated. Furthermore, the phosphors can generate light from yellow-green through white and eventually to blue by properly tuning the relative ratio of Ce³⁺ to Tb³⁺ ions grounded on the principle of energy transfer. The results show that this phosphor has potential applications as a single-phased phosphor for UV white-light LEDs.     

Effect of Eu,Tb codoping on the luminescent properties of Y2O3 nanorods

Red-emitting Y₂O₃:Eu³⁺ and green-emitting Y₂O₃:Tb³⁺ and Y₂O₃:Eu³⁺, Tb³⁺ nanorods were synthesized by hydrothermal method. Their structure and micromorphology have been analyzed by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The photoluminescence (PL) property of Y₂O₃:Eu³⁺,Tb³⁺ phosphor was investigated. In the same host (Y₂O₃), upon excitation with ultraviolet (UV) irradiation, it is shown that there are strong emissions at around 610 and 545 nm corresponding to the forced electric dipole ⁵D₀-⁷F₂ transition of Eu³⁺ and ⁵D₄-⁷F₅ transition of Tb³⁺, respectively. Different qualities of Eu³⁺and Tb³⁺ ions are induced into the Y₂O₃ lattice. From the excitation spectrum, we speculate that there exists energy transfer from Tb³⁺ to Eu³⁺ ions .The emission color of powders reveals regular change in the separation of light emission. These powders can meet with the request of optical display material for different colors or can be potentially used as labels for biological molecules.     

Sensitized luminescence through nanoscopic effects of ZnO encapsulated in SiO2:Tb sol gel derived phosphor

Terbium (1 mol%) doped ZnO-SiO₂ binary system was prepared by a sol-gel process. Nanoscopic effects of ZnO on the photoluminescence (PL) and the cathodoluminescence (CL) properties were studied. Defects emission from ZnO nanoparticles was measured at 560 nm and the line emission from Tb³⁺ ions in SiO₂:Tb³⁺ and ZnO-SiO₂:Tb³⁺ with a major peak at 542 nm was measured. The PL excitation wavelength for 542 nm Tb³⁺ emission was measured at ∼320 nm in both SiO₂:Tb³⁺ and ZnO-SiO₂:Tb³⁺. The CL data showed quenched luminescence of the ZnO nanoparticles at 560 nm from a composite of ZnO-SiO₂:Tb³⁺ and a subsequent increase in 542 nm emission from the Tb³⁺ ions. This suggests that energy was transferred from the ZnO nanoparticles to enhance the green emission of the Tb³⁺ ions. The PL and CL properties of ZnO-SiO₂:Tb³⁺ binary system and possible mechanism for energy transfer from the ZnO nanoparticles to Tb³⁺ ions are discussed.     

Luminescence enhancement by energy transfer from Ce ions in Ba1.6Ca0.4P2O7:Ce:Tb phosphor

The optical properties of Ba_1.6Ca_0.4P₂O₇ doped with Ce³⁺ and Tb³⁺ are investigated. Under excitation at 280 nm the emission spectrum of Ba_1.6Ca_0.4P₂O₇:Ce³⁺ consists of a peak at 370 nm and a shoulder at the longer wavelength side. The emission spectra of Ba_1.6Ca_0.4P₂O₇:Tb³⁺ shows the well-known emission lines due to ⁵D₄-⁷F_J transitions of Tb³⁺. The green emissions of Tb³⁺ ions are enhanced upon UV excitation through energy transfer from Ce³⁺ to Tb³⁺ ions. The efficiency of such an energy transfer is estimated based on spectroscopic data. The dependence of photoluminescence (PL) intensities of Ce³⁺ and Tb³⁺ emissions on Ce³⁺ or Tb³⁺ concentrations in the systems (Ba_1.6Ca_0.4P₂O₇:0.04Ce³⁺,xTb³⁺ and Ba_1.6Ca_0.4P₂O₇:xCe³⁺,0.04Tb³⁺) and the temperature dependence of PL emission spectra of Ba_1.6Ca_0.4P₂O₇:0.06Ce³⁺,0.04Tb³⁺ is also investigated.     

Luminescence and energy transfer of white-light emitting CaAl2SiO6:Ce3+, Tb3+ phosphors

A novel white-light emitting CaAl₂SiO₆: Ce³⁺, Tb³⁺ phosphor has been prepared by a sol–gel method. X-ray diffractometry and spectrofluorometry were used to characterize structural and optical properties of the samples. The results indicate that the crystal structure of the phosphor is a single phase of CaAl₂SiO₆. The excitation band of the phosphor covers a wide region from 240 nm to 380 nm. CaAl₂SiO₆: Ce³⁺, Tb³⁺ phosphors show four emission bands: one at 400 nm for Ce³⁺ and three at 487 nm, 543 nm and 585 nm for Tb³⁺. With appropriate tuning of Tb³⁺ content, white light with different hues can be achieved under UV radiation. The energy transfer mechanism from Ce³⁺ to Tb³⁺ in CaAl₂SiO₆ host was demonstrated to be dipole–dipole interaction.     

Luminescence kinetics in silica gel doped with Tb3+ ions and ZnS:Mn2+ nanocrystals

Luminescence kinetics and time-resolved luminescence spectra of SiO₂, SiO₂ doped with ZnS:Mn²⁺ nanocrystals and SiO₂ doped with ZnS:Mn²⁺, and additionally co-doped with Tb³⁺, are presented. The purposes of the paper are the analysis of the kinetics of the Tb³⁺ and Mn²⁺ intra-shell luminescence and the elucidation of the energy-transfer mechanism between the ZnS:Mn²⁺ nanocrystals and the Tb³⁺ ions. We have found a blue luminescence related to defects in the ZnS nanocrystals and an intrinsic luminescence of the SiO₂ lattice, which decays in few ns. A yellow luminescence related to the Mn^{2+ 4}T₁(G)→⁶A₁ transition and yellow sharp lines related to the ⁵D₄→⁷F₆, ⁷F₅, ⁷F₄ and ⁷F₃ transitions in Tb³⁺ are found to decay in ms. A very effective energy transfer between ZnS:Mn²⁺ nanoparticles and Tb³⁺ ions has been observed.     

Green photoluminescence, but blue afterglow of Tb activated Sr4Al14O25

Tb³⁺ activated Sr₄Al₁₄O₂₅ phosphors were synthesized by the high temperature solid-state reaction. For the sample, the color of the photoluminescence (PL) was green, but that of the afterglow was blue. The spectral results indicated that the photoluminescence was mainly due to the transitions from ⁵D₄ to the ground energy levels of Tb³⁺ and obeyed the cross-relaxation mechanism; however, the afterglow was derived from the transitions from ⁵D₃ and independent with the concentration of Tb³⁺. This difference was attributed to the reason that the energy transfer process of cross-relaxation was halted by the traps during the period of afterglow.     

Enhanced luminescence of Tb by efficient energy transfer from Ce in Sr2B5O9Cl host

Ce³⁺ and Tb³⁺ co-doped Sr₂B₅O₉Cl phosphors with intense green emission were prepared by the conventional high-temperature solid-state reaction technique. A broad band centered at about 315 nm was found in phosphor Sr₂B₅O₉Cl: Ce³⁺, Tb³⁺ excitation spectrum, which was attributed to the 4f-5d transition of Ce³⁺. The typical sharp line emissions ranging from 450 to 650 nm were originated from the ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions of Tb³⁺ ions. The photoluminescence (PL) intensity of green emission from Tb³⁺ was enhanced remarkably by co-doping Ce³⁺ in the Tb³⁺ solely doped Sr₂B₅O₉Cl phosphor because of the dipole-dipole mechanism resonant energy transfer from Ce³⁺ to Tb³⁺ ions. The energy transfer process was investigated in detail. In light of the energy transfer principles, the optimal composition of phosphor with the maximum green light output was established to be Sr_1.64Ce_0.08Tb_0.1Li_0.18B₅O₉Cl by the appropriate adjustment of dopant concentrations. The PL intensity of Tb³⁺ in the phosphor was enhanced about 40 times than that of the Tb³⁺ single doped phosphor under the excitation of their optimal excitation wavelengths.     

Synthesis and photoluminescence of core–shell structured spherical SiO2@YPO4:Tb3+ phosphors via sol–gel process

Monodispersed SiO₂@YPO₄:Tb³⁺ core–shell submicrospheres were prepared through a simply homogeneous sol–gel method. The resulted SiO₂@YPO₄:Tb³⁺ core–shell particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence spectra (PL) and kinetic decays. The XRD results demonstrate that the YPO₄:Tb³⁺ layers begin to crystallize on the SiO₂ spheres after annealing at 500 °C and the crystallinity increases with raising the annealing temperature. The FTIR spectra show that the YPO₄:Tb³⁺ shell has linked to the silica surface through forming a Si–O–Y bond. SEM and TEM analysis indicate that SiO₂@YPO₄:Tb³⁺ core–shell submicrospheres have the regular microstructures and uniform size distributions. The emission spectra of the obtained submicrospheres are dominated by ⁵D₄–⁷F₅ transition of Tb³⁺ (545 nm, green), and the emission intensities of Tb³⁺ increase with increasing the annealing temperatures and the number of coating cycles. The optimum concentration for Tb³⁺ was determined to be 5 mol % of Y³⁺ in YPO₄ host.