A single-phase Na1+x+yCa1-2x-2yPO4: xCe3+, yTb3+ phosphor is developed, achieving both superior thermal stability and color tunability for white LEDs. Remarkably, it retains 89% of its room-temperature intensity at 423 K, outperforming most reported Ce3+/Tb3+ co-activated systems. This robustness is attributed to a high thermal quenching activation energy (Ea = 0.230 eV) and an ultra-small chromaticity shift (ΔS = 3.6 × 10−3, 300–500 K). Meanwhile, efficient dipole-dipole energy transfer from Ce3+ to Tb3+ enables continuous emission tuning from blue to green by simply adjusting the Tb3+ content. These features make this phosphor a promising green-emitting candidate for white LEDs.

Ce3+, Sm3+ singly-doped and Ce3+-Sm3+ co-doped sodium yttrium borate Na3Y(BO3)2 phosphors are prepared using a high temperature solid-state reaction route, in order to investigate their spectroscopic properties, luminescence dynamic and energy transfer mechanisms. The weak electron-vibrational interaction (EVI) between Ce3+ ions and their surroundings is demonstrated according to measured spectra and theoretical analysis. The mechanism of the Ce3+ → Sm3+ energy transfer in the host is investigated via luminescence dynamic models. In addition, the potential application of Ce3+-Sm3+ co-doped Na3Y(BO3)2 phosphors in the optical anti-counterfeiting is demonstrated according to the luminescence regulation of excitation wavelength response.

The phosphors Ba2Mg(BO3)2 activated with Ce3+ and Eu2+ ions are prepared by a solid-state reaction method at high-temperature and the Rietveld structure refinement of the host compound is performed. The synchrotron radiation VUV - UV excitation, UV – vis emission and luminescence decay spectra, as well as the dependencies of luminescence intensity and lifetime on doping content and temperature are systematically investigated. In addition, the electron-vibrational interaction (EVI) of Eu2+ ions with coordination surroundings and the Ce3+→Eu2+ energy transfer (ET) dynamics are studied in detail. Based on above discussion, the potential applications of co-doped phosphors in excitation wavelength and temperature dual-response optical anti-counterfeiting are demonstrated.

Cationic tuning for lanthanide (Ce3+/Pr3+)-activated inorganic phosphors with stable, efficient, and fast-decay 5d-4f emissions has emerged as an important strategy toward the continuing pursuit of superior scintillators. The in-depth understanding of the cationic effects on photo- and radioluminescence of lanthanides Ce3+ and Pr3+ centers is requisite for the rational cationic tuning. Here, we perform a systematic study on the structure and photo- and X-ray radioluminescence properties of K3RE(PO4)2:Ce3+/Pr3+ (RE = La, Gd, and Y) phosphors to elucidate the underlying cationic effects on their 4f-5d luminescence. By using the Rietveld refinements, low-temperature synchrotron-radiation vacuum ultraviolet-ultraviolet spectra, vibronic coupling analyses, and vacuum-referred binding energy schemes, the origins of lattice parameter evolutions, 5d excitation energies, 5d emission energies, and Stokes shifts as well as good emission thermal stabilities of K3RE(PO4)2:Ce3+ systems are revealed. In addition, the correlations of Pr3+ luminescence to Ce3+ in the same sites are also discussed. Finally, the X-ray excited luminescence manifests that the K3Gd(PO4)2:1%Ce3+ sample possesses a light yield of ∼10,217 photons/MeV, indicating its potentiality toward X-ray detection application. These results deepen the understanding of cationic effects on Ce3+ and Pr3+ 4f-5d luminescence and inspire the inorganic scintillator development.

Transparent displays (TDs) rendering “levitating” images on screen have appeared as an emerging technology toward augmented/mixed reality applications. However, the traditional phosphor design and screen construction have severely limited the TD performance owing to the lack of efficient narrow‐band blue emitters and stable screen structure. Herein, the novel narrow‐band (full width at half maximum: 32 nm) NaLi 3 SiO 4 :Eu 2+ phosphor with a peak at 467 nm as a key blue emitter is explored, and it is sandwiched in layered film as a unique screen design. The devised screen features decent transparency, high emission color purity, and good reliability, and the TD prototype renders “floating” static images and vivid animation with broad viewing angle (15°–165°) and large color gamut (97% of National Television Standards Committee). Spectroscopic and microstructural characterizations reveal the TD superior performance originates from synergistic contributions of moderate crystal field effect (ε c ≈ 1.13 eV; ε cfs ≈ 1.60 eV), weak vibronic coupling ( S ≈ 3; ħω ≈ 285 cm −1 ), and limited thermal ionization of 5d electrons ( E a ≈ 0.43 eV) for NaLi 3 SiO 4 :Eu 2+ emission and layered architecture for screen film. These findings establish fundamental guidelines for narrow‐band emitting materials design and shine light on superior TD innovative development.

Ce3+-doped LiSr4(BO3)3phosphors have been prepared by a high-temperature solid-state reaction method, andstructural refinement of the host compound has been performed.The excitation and emission spectra in the vacuum ultraviolet-ultraviolet-visible range at cryogenic temperatures reveal that Ce3+ions preferentially occupy eight-coordinated Sr2+sites inLiSr4(BO3)3. Such experimental attribution is well corroboratedby the calculated 4f-5d transition energies and defect formationenergies of Ce3+ions at two distinct Sr2+sites in thefirst-principlesframework. In addition, the doping concentration-dependentluminescence and the temperature-dependent luminescence aresystematically investigated by luminescence intensity and lifetimemeasurements, respectively. This shows that concentration quenching does not occur in the investigated doping range, butinhomogeneous broadening exists in the concentrated samples. With the estimated thermal quenching activation energy, thediscussions on the thermal quenching mechanisms suggest that the thermal-ionization process of the 5d electron is a dominantchannel for thermal quenching of Ce3+luminescence, despite the fact that thermally activated concentration quenching cannot beexcluded for the highly doped samples. Finally, the X-ray excited luminescence measurement demonstrates the promisingapplications of the phosphors in X-ray detection

采用高温固相方法合成了不同浓度Tb3+掺杂的单斜结构K3La(PO4)2荧光粉,利用XRD表征了其相纯度,并对基质化合物进行了结构精修.研究了Tb3+掺杂样品在不同温度下的发光性质及不同掺杂浓度样品在室温下的发光性质.发现在室温、373 nm激发下,Tb3+离子表现为5D3-7FJ(J=5,4,3,2)和5D4-7FJ'(J'=6,5,4,3)等两组发射.不同温度下低掺样品的光谱测试表明,多声子弛豫对5D3能级发射的猝灭贡献有限.随着掺杂浓度增加,Tb3+离子5D3发射减弱而5D4发射增强,样品表现出从青光到绿光的光色调控性质,这主要是由Tb3+能级间的交叉弛豫过程导致的;进一步通过Inokuti-Hirayama模型和扩展的Yokota-Tanimoto模型对5D3发光衰减曲线进行拟合,结果表明能量传递的主要作用方式为电偶极-四极作用,临界传递距离约为1.03 nm.

Palette for security. The “concentration palette” strategy enables the design of lanthanide-activated phosphors with temperature-responsive colour and orange intensity co-evolution, which are also used to fabricate superior security tag prototypes.

Ce3+ and Eu2+ doped and Ce3+-Eu2+ co-doped Sr2MgSi2O7 phosphors are prepared via a high-temperature solid-state reaction technique. The synchrotron radiation vacuum ultraviolet-ultraviolet (VUV-UV) excitation and ultraviolet-visible (UV-vis) emission spectra of diluted Ce3+ and Eu2+ doped Sr2MgSi2O7 samples are measured at cryogenic temperatures. The electron-vibrational interaction (EVI) between Ce3+ and its surroundings is analyzed. The dependencies of the 4f-5d transitions of Ce3+ on the structure of the host compounds Sr2MgSi2O7, Ba2MgSi2O7 and BaMg2Si2O7 are discussed in detail. Then the thermal quenching channel is proposed based on the measurements of temperature dependent luminescence intensities and decay times of Ce3+ and Eu2+ in Sr2MgSi2O7, and the Ce3+ → Eu2+ energy transfer mechanism is understood by three luminescence dynamic models. In addition, Sr2MgSi2O7:Ce3+/Eu2+ samples are evaluated for the possibilities of X-ray detection applications using X-ray excited luminescence (XEL) spectroscopy, and it was found that they are not suitable.

Sm3+ and Ce3+ singly doped and Sm3+ and Ce3+ co-doped Sr3B2O6 phosphors are prepared via a high-temperature solid-state reaction method. The crystal structure and phase purity are characterized by X-ray diffraction (XRD) analyses. The Sm3+-doped sample displays an emission in the orange-red region, with the strongest emission line at about 648 nm and possessing a good luminescence thermal stability between 78 and 500 K. With the increase in the Sm3+ content, the concentration quenching is observed due to the cross-relaxation (CR) processes among the Sm3+ ions. Upon 340 nm excitation, the Ce3+-doped phosphor presents a broad emission band in the blue region with a maximum at about 420 nm, which overlaps well with the 6H5/2 → 6P3/2 excitation line of Sm3+ and implies the possible energy transfer from Ce3+ to Sm3+. The spectral and decay measurements of the Ce3+ and Sm3+ co-doped samples are conducted and the Inokuti–Hirayama (I-H) model is adopted to analyze the luminescence decay dynamics of the donor Ce3+. Owing to the evident sensitization of the Sm3+ by the Ce3+ ions, the co-doped samples exhibit color variation under different wavelength excitations, endowing them with potential applications in optical anti-counterfeiting.

Eu2+-, Mn2+- and Eu2+-Mn2+-doped CaMgSi2O6 phosphors have been prepared by a high-temperature solid-state reaction. Systematic investigation of the concentration- and temperature-dependent luminescence of Mn2+ showed that Mn2+ ions occupy two distinct sites in CaMgSi2O6. Electron-vibration interaction (EVI) analyses of Mn2+ ions revealed Huang-Rhys factors of 4.73 and 2.82 as well as effective phonon energies of 313 and 383 cm(-1) for the two sites. Eu2+-Mn2+ energy transfer is also discussed, and its efficiency is estimated by lifetime and luminescence spectra. The different thermal quenching behaviours of Eu2+ and Mn2+, the distinct emission colours of Eu2+ (blue, band peak at similar to 451 nm) and Mn2+ (yellow-red range, band peaks at similar to 583 and 693 nm) endow the co-doped samples with potential applications in luminescence thermometry and temperature-/excitation wavelength-responsive dual anti-counterfeiting.

Luminescent materials with controllable colour evolution features are demanded for the development of multi-level anti-counterfeiting technologies. Here we report the structural and luminescence properties of CaMgSi2O6:Ln (Ln = Eu2+, Eu3+, Eu2+/3+) samples in detail and reveal their excitation-wavelength/temperature driven colour evolution characteristics. By tuning either the excitation-wavelength (276, 304, 343, 394 nm) or temperature (in the 330-505 K range), the designed samples with co-existing Eu2+/Eu3+ ions can achieve diverse and controllable colour evolution from red, to pink, purple and blue. This shows their potential application in anti-counterfeiting with the help of sophisticated pattern design. In addition, the underlying mechanism of the Stokes shift of the Eu2+ emission and valence stability of both Eu2+/Eu3+ ions in CaMgSi2O6 are also studied in depth. These results are valuable for designing colour-controllable luminescent materials based on the co-existence of the Eu2+/Eu3+ ions for anti-counterfeiting applications.

Ce3+ and Eu2+ single- and double-doped CaMgSi2O6 phosphors have been prepared by a high-temperature solid-state reaction approach. The VUV–UV–vis luminescence properties are investigated at cryogen...

Ce³⁺ and Eu²⁺ single- and double-doped CaMgSi₂O₆ phosphors have been prepared by a high-temperature solid-state reaction approach. The VUV–UV–vis luminescence properties are investigated at cryogenic temperatures. The dependencies of luminescence intensity and lifetime on temperature are discussed in detail, and the different thermal-quenching characteristics of luminescence of Ce³⁺ and Eu²⁺ in CaMgSi₂O₆ are revealed combined with the VRBE scheme. Because of the different energy barriers of the lowest 5d energy and the conduction band bottom, luminescence thermal quenching of Ce³⁺ does not occur below about 505 K, but that of Eu²⁺ arises at a temperature above ∼300 K. The energy transfer dynamics is then analyzed by using the Inokuti-Hirayama, Yokota-Tanimoto, and Burshtein models, respectively. The Ce³⁺–Eu²⁺ energy transfer is mainly through the electric dipole–dipole interaction with a critical distance of about 21.2 A, and the energy migration between Ce³⁺ ions in a fast or slow way is negligible. The different thermal-quenching behaviors of Ce³⁺ and Eu²⁺ luminescence and their energy transfer pave the way for the potential applications of the codoped samples in optical thermometry and anticounterfeiting.

RbBaPO4:Eu2+ phosphors have been prepared by a high-temperature solid-state reaction method, and the structure was determined by Rietveld refinement based on powder X-ray diffraction (P-XRD) data. Their VUV-UV-vis photoluminescence properties are systematically investigated with three objectives: (1) based on low-temperature spectra, we clarify the site occupancies of Eu2+, and demonstrate that the doublet emission bands at ∼406 and ∼431 nm originate from Eu2+ in Ba2+ [Eu2+(I)] and Rb+ [Eu2+(II)] sites, respectively; (2) an electron-vibrational interaction (EVI) analysis is conducted to estimate the Huang-Rhys factors, the zero-phonon lines (ZPLs) and the Stokes shifts of Eu2+ in Rb+ and Ba2+ sites; (3) the studies on luminescence decay of Eu2+(I) reveal that dipole-dipole interaction is mainly responsible for the energy transfer from Eu2+(I) to Eu2+(II), and the energy migration between Eu2+(I) is weak. Finally, the X-ray excited luminescence (XEL) spectrum indicates that the light yield of the sample RbBa0.995Eu0.005PO4 is ∼17 700 ph/MeV, showing its potential application in X-ray detecting.

Optical multiplexing based on luminescent materials with tunable color/lifetime has potential applications in information storage and security. However, the available tunable luminescent materials reported so far still suffer from several drawbacks of low efficiency or poor stability, thus restraining their further applications. Herein, we demonstrate a strategy to develop efficient and stable lanthanide coordination polymers (LCPs) with tunable luminescence as a new option for optical multiplexing. Their multicolor emission from green to red and naked-eye-sensitive green emission with tunable lifetime (from ca. 300 to ca. 600 μs) can be controlled by host differential sensitization and energy transfer between lanthanide ions. The quantum efficiencies of developed samples range from around 20 % to 46 % and the luminescence intensity/lifetime appear quite stable in polar solvents up to ten weeks. Furthermore, with the aid of inkjet printing and concepts of luminescence lifetime imaging and time-gated imaging, we illustrate their promising applications of information storage and security in spatial and temporal domains.

Tuning of phosphor luminescence properties, including the emission energy/intensity and thermal stability, is an important way to develop superior luminescent materials for diverse applications. In this work, we discuss the effect of band gap engineering and energy transfer on the luminescence properties of Ce3+ or Pr3+ doped (Y,Gd)AGG systems, and analyze the underlying reasons for their different phenomena. By using VUV-UV excitation spectra and constructing VRBE schemes, the changes of host band structure, 5d excited level energies and emission thermal stability of Ce3+ and Pr3+ with the incorporation of Gd3+ ions were studied. In addition, the energy transfer dynamics was also investigated in terms of the luminescence decay curves. This work demonstrates a way to tune phosphor luminescence properties by combining band gap engineering and energy transfer tailoring and provides an inspiring discussion on the different results of Gd3+ doping on the Ce3+ and Pr3+ emissions.

In this work, the coordination polyhedron stabilities and distributions of europium ions in Ca6BaP4O17 (CBPO) luminescent materials are investigated. The density functional theory (DFT)-based first principles calculation results show that the PO4 tetrahedrons can tilt in the structure, which leads to the atomic distortion of O13 and O12 in CBPO and the Eu2+/Eu3+-doped systems. The energy scale of about ∼0.1 eV suggests that stabilities of coordination polyhedrons are easily influenced by dynamic factors. The atomic distortion and vacancy of work as charge compensations in CBPO:Eu3+, and three lattice sites of europium are extracted and summarized. The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) confirm that Eu3+ can occupy the Ca1, Ca2 and Ba sites of CBPO. The combination of first principles calculation and X-ray absorption fine structure (XAFS) provides more information about microstructures of luminescent materials.

The clustering of trivalent lanthanide-doped fluorite was divided into four stages. Characters of the first three stage discrete clusters were studied by the density functional theory (DFT) based first principles calculation in the work. The results revealed the relative stabilities of first stage C(4v )and C-3v were intimately correlated with that of the second and third stage clusters. The more stable C-4v with interstitial F-i(-) at the nearest site would stabilize the second cubic sublattice centers and C-3v with F-i(-) at next nearest site for the third square antiprism clusters. The lattice mismatch and projected density of states (pDOS) results indicated that coupling of electrostatic, strain, bonding and hybridization among F-i(-), RE3+ and surrounded lattice anions controlled the site occupation and the correlations. The clusters and clustering features could be modulated and utilized to tune up- and down-conversion photoluminescence for designing of new lanthanide-doped fluorite materials.