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.     

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 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 luminescent properties of Y3Al5O12:Tb,Ce phosphor prepared by spray pyrolysis

Yttrium aluminum garnet (YAG) particles doped with Tb³⁺ or double doped with Tb³⁺ and Ce³⁺ were prepared by spray pyrolysis and characterized by photo- and cathode-luminescence. It was tried to incorporate a broad band of Ce³⁺ activator into the line peaks of Tb³⁺ in YAG host without the reduction of emission intensity. Ce-codoped YAG:Tb particles showed a broad band emission due to the d-f transition of Ce³⁺ and a reduction in the intensity of emission peaks due to ⁵D₃-⁷F_j (j=3, 4, 5, 6) transition of Tb³⁺ when they were excited by the ultraviolet light of 270 nm. These results supported that an effective energy transfer occurs from Tb³⁺ to Ce³⁺ in YAG host. Codoping Ce³⁺ ions greatly intensified the excitation peak at 270 nm for the emission at 540 nm of Tb³⁺, which means that more lattice defects, involving in the energy absorption and transfer to Tb³⁺, are formed by the Ce³⁺ codoping. The finding gives a promising approach for enhancing the luminescence efficiency.     

Eu3+ emission in SrAl2B2O7 based phosphors

Eu³⁺ doped SrAl₂B₂O₇ phosphors were fabricated by the wet method. The structures of the phosphors were characterized by XRD. The doping content of Eu³⁺ ions in SrAl₂B₂O₇:Eu³⁺ phosphors are 1%, 4%, 6%, 8%, 10% (molar fraction), respectively. Luminescence properties were analyzed by measuring the excitation and photoluminescence spectra. The luminescent properties of SrAl₂B₂O₇:Eu³⁺ phosphors are discussed. It is shown that from 4% to 6% of doping content of Eu³⁺ ions under 392 nm excitation in SrAl₂B₂O₇:Eu³⁺ phosphors is optimum.     

Luminescence and Tb-Ce-Eu ion energy transfer in single-crystalline films of Tb3Al5O12:Ce,Eu garnet

The paper is devoted to investigation of the processes of excitation energy transfer between the host cations (Tb³⁺ ions) and the activators (Ce³⁺ and Eu³⁺ ions) in single-crystalline films of Tb₃Al₅O₁₂:Ce,Eu (TbAG:Ce,Eu) garnet which is considered as a promising luminescent material for the conversion of LED's radiation. The cascade process of excitation energy transfer is shown to be realized in TbAG:Ce,Eu: (i) from Tb³⁺ ions to Ce³⁺ and Eu³⁺ ions; (ii) from Ce³⁺ ions to Eu³⁺ ions by means of dipole-dipole interaction and through Tb³⁺ ion sublattice.     

White-light long-lasting phosphorescence from Tb-activated Y2O2S phosphor

The white-light long-lasting phosphors Y₂O₂S:Tb³⁺, Sr²⁺ or/and Zr⁴⁺ were prepared and studied. The white-light afterglow emission after the irradiation with 254 nm UV are composed of the blue light emission and the yellowish-green light emission, originating from the transitions of ⁵D₃→⁷F₅, ⁵D₄→⁷F₅ in Tb³⁺ when the Tb³⁺ concentration is not higher than 0.3 at%. The codoped Sr²⁺ and Zr⁴⁺ ions act as trap-creating ions. The afterglow can last over 21 min in the dark for Y₂O₂S:Tb³⁺0.3%, Sr²⁺4%, Zr⁴⁺4% after irradiation by 254 nm ultraviolet light. Y₂O₂S:Tb³⁺ may be a promising material for the development of white-light long-lasting phosphor since the Tb³⁺ has a high luminescent efficiency and the dominant excitation band of 4f →5d is located at 220-300 nm.     

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.     

Quenching of thermo-stimulated photo-ionization by energy transfer in CaAl4O7: Tb, Ce

Crystal fibers of Ce³⁺ and Tb³⁺ singly doped and co-doped CaAl₄O₇ were grown by the LHPG method. Photoluminescence, excitation spectra and photoconduction were measured. Thermo-stimulated photo-ionization (delocalization) of electrons from the lowest field component of the 5d excited state of Ce³⁺ was observed in the Ce³⁺ singly doped sample under excitation at 355 nm. The 5d sublevel was found to locate at 0.3 eV below the conduction band of the host. However, the thermo-stimulated photo-ionization was greatly quenched due to the fast energy transfer from the 5d sublevel to Tb³⁺ ions in the Ce³⁺/Tb³⁺ double doped sample.     

New red phosphors BaZr(BO3)2 and SrAl2B2O7 doped with Eu for PDP applications

Vacuum ultraviolet (VUV) excitation and photoluminescence (PL) characteristics of Eu³⁺ ion doped borate phosphors; BaZr(BO₃)₂:Eu³⁺ and SrAl₂B₂O₇:Eu³⁺ are studied. The excitation spectra show strong absorption in the VUV region with the absorption band edge at ca. 200 nm for BaZr(BO₃)₂:Eu³⁺ and 183 nm for SrAl₂B₂O₇:Eu³⁺, respectively, which ensures the efficient absorption of the Xe plasma emission lines. In BaZr(BO₃)₂:Eu³⁺, the charge transfer band of Eu³⁺ does not appear strongly in the excitation spectrum, which can be enhanced by co-doping Al³⁺ ion into the BaZr(BO₃)₂ lattices. The luminescence intensity of BaZr(BO₃)₂:Eu³⁺ is also increased by Al³⁺ incorporation into the lattices. The PL spectra show the strongest emission at 615 nm corresponding to the electric dipole ⁵D₀→⁷F₂ transition of Eu³⁺ in both BaZr(BO₃)₂ and SrAl₂B₂O₇, similar to that in YAl₃(BO₃)₄, which results in a good color purity for display applications.     

Red emission in B- and Li-doped SrAl2O4:Eu phosphor under UV excitation

Samples of SrAl₂O₄:Eu³⁺ doped with B³⁺ and SrAl₂O₄:Eu³⁺ co-doped with B³⁺ and Li⁺ have been prepared by the solid-reaction method. The influence of B³⁺ and Li⁺ contents on luminescence property has been investigated. It is found that the substitution of B³⁺ for Al³⁺ greatly improves red emission intensity at 591, 615 and 701 nm. The dopant Li⁺ as charge compensator in SrAl₂O₄:Eu³⁺, B³⁺ can further enhance luminescence intensity. The strongest red emission is obtained in the Sr(Al_1.9, B_0.1)O₄:Eu_0.02³⁺, Li⁺_0.02 sample. The developed phosphors can be efficiently excited by ultraviolet (UV) light from 350 to 480 nm, which indicates that B³⁺ and Li⁺ co-doped SrAl₂O₄:Eu³⁺ is a good candidate phosphor applied in solid-state lighting in conjunction with white UV light-emitting diodes (LEDs).     

SrAl_2B_2O_7:Dy~(3+)材料的制备及其发光性能

采用高温固相法制备了SrAl2B2O7:Dy3+发光材料.在350nm紫外光激发下,测得SrAl2B2O7:Dy3+材料的发射光谱为一个多峰宽谱,主峰分别为480,573和678nm;分别和Dy3+的4F9/2→6H15/2,4F9/2→6H13/2,4F9/2→6H11/2的跃迁发射相对应;监测573nm的发射峰,得到材料的激发光谱为一个多峰宽谱,主峰分别为295,325,350,365,400nm.研究了Dy3+掺杂浓度对SrAl2B2O7:Dy3+材料发射光谱的影响,随着Dy3+掺杂浓度的增大,SrAl2B2O7:Dy3+材料的Iy/Ib逐渐增大,根据Judd-Ofelt理论解释了其原因.随着Dy3+掺杂浓度的增大,Dy3+的4F9/2→6H13/2跃迁产生的573nm发射峰强度先增大,在4%时达到最大值,之后减小,其自身的浓度猝灭机理为电偶极-电偶极相互作用.不同的电荷补偿剂Li+,Na+,K+的引入均使发光强度得到提高,尤其以Li+最佳,发光强度提高了大约33%.     

A novel blue-emitting phosphor: BaAl2B2O7: Pb

Pb²⁺ doped BaAl₂B₂O₇ materials were prepared by a solution combustion synthesis. The phase of the synthesized materials was determined using the powder X-ray diffraction. The photoluminescent properties of Pb²⁺ doped BaAl₂B₂O₇ materials were investigated using spectrofluorometer at room temperature. The emission and excitation bands of BaAl₂B₂O₇: Pb²⁺ were observed at 423 and 266 nm, respectively. The dependence of the emission intensity on the Pb²⁺ concentration for BaAl₂B₂O₇: Pb²⁺ was investigated. The Stokes shifts of BaAl₂B₂O₇: Pb²⁺ was calculated to be 13 953 cm⁻¹.     

Synthesis and luminescence investigation of RE (Eu, Tb and Ce)-doped lithium silicate (Li2SiO3)

Synthesis and photoluminescence (PL) investigations of lithium metasilicate doped with Eu³⁺, Tb³⁺ and Ce³⁺ were carried out. PL spectra of Eu-doped sample showed peaks corresponding to the ⁵D₀→⁷F_j (j=1, 2, 3 and 4) transitions under ultraviolet excitation. Strong red emission coming from the hypersensitive ⁵D₀→⁷F₂ transition of Eu³⁺ ion suggested the presence of the dopant ion in structurally disordered environment. Tb³⁺-doped silicate sample showed blue-green emission corresponding to the ⁵D₄→⁷F_j (j=6, 5 and 4) transitions. Ce-doped sample under excitation from UV, showed a broad emission band in the region 350-370 nm with shoulders around 410 nm. The fluorescence lifetimes of Eu³⁺ and Tb³⁺ ions were found out to be 790 and 600 μs, respectively. For Ce³⁺, the lifetime was of the order of 45 ns. PL spectra of the europium- and terbium-doped samples were compared with commercial red (Y₂O₃:Eu³⁺) and green (LaPO₄:Tb³⁺) phosphors, respectively. It was found that the emission from the doped silicate sample was 37% of the commercial phosphor in case of the Tb-doped sample and 8% of the commercial phosphor in case of the Eu-doped sample.     

Efficient fluorescence of dissolved CaF2:Tb and CaF2:Ce, Tb nanoparticles through surface coating sensitization

Oleic acid (OA)-modified CaF₂:Tb³⁺ nanoparticles with various Tb³⁺ concentrations and CaF₂:Ce³⁺, Tb³⁺ nanoparticles were synthesized. The as-prepared nanoparticles were shown to be well dissolved in some common organic solvents, such as chloroform and toluene. The nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD) and transmission electron microscopy (TEM). The investigation of fluorescence properties of CaF₂:Tb³⁺ nanoparticles showed that the Tb³⁺ ions could be sensitized efficiently by the surface coating of OA and CaF₂:Tb³⁺ nanoparticles with 10 mol% Tb³⁺ concentrations possess the highest emission intensity. The comparison of emission for CaF₂:Ce³⁺, Tb³⁺ and CaF₂:Tb³⁺ (10 mol%) nanoparticles revealed that the emission intensity of the former is about 4.5 times as strong as that of the latter.     

Photoluminescence properties and effects of dopant concentration in Bi2ZnB2O7:Tb phosphor

A novel green phosphor, Tb³⁺ doped Bi₂ZnB₂O₇ was synthesized by conventional solid state reaction method. The phase of synthesized materials was determined using the XRD, DTA/TG and FTIR. The photoluminescence characteristics were investigated using spectrofluorometer at room temperature. Bi₂ZnB₂O₇:Tb³⁺ phosphors excited by 270 nm and 485 nm wavelengths. The emission spectra were composed of three bands, in which the dominated emission of green luminescence Bi₂ZnB₂O₇:Tb³⁺ attributed to the transition ⁵D₄ → ⁷F₅ is centered at 546 nm. The dependence of the emission intensity on the Tb³⁺ concentration for the Bi_2−xTb_xZnB₂O₇ (0.01 ≤ x ≤ 0.15) was studied and observed that the optimum concentration of Tb³⁺ in phosphor was 13 mol% for the highest emission intensity at 546 nm.     

The effect of Ce3+ ions on the spectral and decay characteristics of luminescence phosphate-borate glasses doped with rare-earth ions

The luminescent characteristics of Li₂O-B₂O₃-P₂O₅-CaF₂ (LBPC) glasses doped with Gd³⁺ and Tb³⁺ ions and codoped with Ce³⁺ are studied by pulsed optical spectrometry under electron beam excitation. It is found that in glass with Ce³⁺ and Gd³⁺ ions a decrease in the decay time of gadolinium luminescence in the 312-nm band (⁶ P _J → ⁸ S _7/2) was observed. It is shown that in the glass LBPC: Tb, Ce, an increase in the emission intensity in the main radiative transitions in terbium ion was observed. In the kinetics of luminescence band 545 nm of LBPC: Tb, Ce glasses, is present stage of buildup, the character of which changes with the doped of Ce³⁺ ions. The mechanism of energy transfer in LBP glasses doped with rare elements is discussed.     

Cerium and terbium luminescence in LaMgAl11O19

Under 254 nm excitation LaMgAl₁₁O₁₉ : Ce³⁺ shows emission peaking between 340 and 360 nm with a quantum efficiency up to 65%, which is almost independent of the Ce³⁺ concentration. Energy transfer between the Ce³⁺ ions is not efficient. In CeMgAl₁₁O₁₉ : Tb³⁺ efficient energy transfer occurs from Ce³⁺ to Tb³⁺, resulting in a green emission with a quantum efficiency up to 65%. The Ce³⁺ - Tb³⁺ energy transfer is ascribed to electric dipole-quadrupole interaction.     

Energy transfer from benzoic acid to lanthanide ions in benzoic acid-functionalized lanthanide-doped CaF2 nanoparticles

The preparation of benzoic acid-functionalized CaF₂:Ln³⁺ (Ln = Eu or Tb) nanoparticles and their sensitized luminescence are described in this report. First, to achieve sufficient proof for energy transfer from benzoic acid (BA) to lanthanide ions doped in nanoparticles, we employ Eu³⁺ as the microscopic probe and investigate the luminescent spectra of benzoic acid-functionalized CaF₂:Eu³⁺ (BA-CaF₂:Eu³⁺) nanoparticles. Next, to further reveal the difference between sensitized luminescence and common luminescence for Eu³⁺ doped in CaF₂ nanoparticles, we study the emission spectra of BA-CaF₂:Eu³⁺ nanoparticles excited at 286 nm and 397 nm, respectively. Finally, we analyze and compare the luminescent spectra of BA-CaF₂:Tb³⁺ and CaF₂:Ce³⁺, Tb³⁺ nanoparticles in detail. Our results indicate that both Eu³⁺ and Tb³⁺ doped in CaF₂ nanoparticles can be efficiently sensitized through benzoic acid.     

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.