near-UV Excitation Research Articles

Novel Eu3+-Doped Glasses in the MoO3-WO3-La2O3-B2O3 System: Preparation, Structure and Photoluminescent Properties.

Novel multicomponent glasses with nominal compositions of (50-x)MoO3:xWO3:25La2O3:25B2O3, x = 0, 10, 20, 30, 40, 50 mol% doped with 3 mol % Eu2O3 were prepared using a conventional melt-quenching method. Their structure, thermal behavior and luminescent properties were investigated by Raman spectroscopy, differential thermal analysis and photoluminescence spectroscopy. The optical properties of the glasses were investigated by UV-vis absorption spectroscopy and a determination of the refractive index. Physical parameters such as density, molar volume, oxygen molar volume and oxygen packing density were determined. The glasses are characterized by a high glass transition temperature. Raman analysis revealed that the glass structure is built up mainly from tetrahedral (MoO4)2- and (WO4)2- units providing Raman bands of around 317 cm-1, 341-352 cm-1, 832-820 cm-1 and 928-935 cm-1. At the same time, with the replacement of MoO3 with WO3 some fraction of WO6 octahedra are produced, the number of which increases with the increasing WO3 content. A strong red emission from the 5D0 level of Eu3+ ions was registered under near-UV (397 nm) excitation using the 7F0 → 5L6 transition of Eu3+. Photoluminescence (PL) emission gradually increases with increasing WO3 content, evidencing that WO3 is a more appropriate component than MoO3. The integrated fluorescence intensity ratio R (5D0 → 7F2/5D0 → 7F1) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites. All findings suggest that the investigated glasses are potential candidates for red light-emitting phosphors.

Novel Orange-Emitting YPO4:Sm3+/Polymer Nanocomposite Phosphor Films for LED Applications.

A polymer based nanocomposite (NC) material embedded with highly luminescent nanopowders could be promising for replacing traditional luminescent materials from a technological pointof view.In this study, we have successfully obtained YPO4: Sm3+ /Polymer nanocomposite phosphor films by embedding YPO4: Sm3+ luminescent nanoparticles (NPs) for orange-light emitting diode (LED) applications. These luminescent NPs were synthesized using the sol gel method in different polymer matrices i.e. polystyrene (PS) and poly (methyl methacrylate) (PMMA) by using direct solution mixing. The structural, morphological, and photoluminescence characteristics of the nano-phosphors and resulting NC films were examined and discussed. The emission spectra of YPO4: Sm3+ (x at.%) nano-phosphors under near-UV excitation at 404nm were dominated by orange emission attributed to 6H5/2 4F7/2 (601nm) luminescence of Sm3+ ions. The optimum doping concentration of activator Sm3+ in YPO4 matrix was found to be 5 at.%. When the doping concentration of Sm3+ was higher than 5 at.%, concentration quenching occurred. The incorporation of YPO4: Sm3+ NPs into polymer matrices indicated that the NCs retained the original luminescence properties of the luminescent NPs, although a decrease in their emission intensity was observed for the NC films, attributable to a polymer matrix effect, which dominated in PS matrix. The fluorescence decay times of NPs in the NC films were measured and compared to those of proper YPO4: Sm3+ nano-phosphors. A decrease in decay time in NC film was observed due the effective refractive index effect. Temperature-dependent photoluminescence (TDPL) of PMMA NC film was studied in 100-400K range, investigating the thermal stability of the film. Additionally, CIE coordinates confirmed the red-orange light emission of the prepared phosphors and NC films. The obtained results indicate that the synthesized polymer-nanophosphor NC films are promising candidates for orange-LED applications.

A novel mixed metal orthoborate Ba2ZnTb2(BO3)4: Crystal structure and multicolor emitting properties introduced by Eu3+ doping

Novel mixed metal orthoborate Ba2ZnTb2(BO3)4 was obtained through the high-temperature solid-state reaction at 950 °C. Its crystal structure was determined by single-crystal X-ray diffraction for the first time. The compound crystallizes in the orthorhombic system, Pbca space group, with cell parameters a = 13.4360(1), b = 6.4539(1), c = 25.3262(2) Å, V = 2196.15(4) Å3 and Z = 8. It represents a novel structure type in which ZnO4 tetrahedra and TbO8 polyhedra are interconnected via corner-, edge-, and face-sharing to form 1D [Zn2Tb4O24]n32n− chains. Some B atoms reside in triangular voids of the chains to strengthen the structure, while the others ‘stitch’ the chains together via B–O bonds to create a 3D [Zn2Tb4(BO3)8]n8n− network, with the open channels hosting Ba2+ ions. In addition, polycrystalline samples of Ba2ZnTb2-2xEu2x(BO3)4 (0 ≤ x ≤ 1) were synthesized via solid-state reaction at 780 °C and systematically characterized by powder XRD combined with Rietveld refinements, SEM, IR/Raman, XPS and photoluminescence spectroscopy. As it was revealed, due to the Tb3+ → Eu3+ energy transfer, the emission color of the obtained phosphors can be continuously tuned from green (0.2947, 0.5876) to orange (0.5766, 0.3994) and eventually to red (0.6419, 0.3536) upon the near-UV excitation at 377 nm through changing the Eu3+/Tb3+ ratio. The representative Ba2ZnTb1.998Eu0.002(BO3)4 sample shows a QY of ∼14.84 % (λex = 377 nm), and its emission intensity at 423 K still maintains ∼66 % of that at 303 K. All these observations indicate that, by properly doping activators and selecting the excitation wavelength, this borate phosphor displays multicolor tunable emission that may have potential applications in multicolor lighting and color display.

Optimization and luminescence studies of Sm3+ doped LiCaBO3 phosphors for high-performance white light-emitting diodes

An undoped and a series of orange-red emitting LiCaBO3:Sm3+ (x = 0.5–3 mol%) phosphors have been synthesized using a highly reliable and cost-effective combustion method. The synthesized phosphors were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL), and Diffuse Reflectance spectroscopy (DRS). The structural studies of the LiCaBO3:Sm3+phosphor confirm the single-phase orthorhombic structure with space group Pbca and the presence of borate anionic groups. Upon near-UV excitation at 405 nm, the PL emission spectra show four emission peaks centered at 564 nm, 602 nm, 650 nm, and 708 nm corresponding to the 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 → 6H9/2 and 4G5/2 → 6H11/2 transitions respectively resulting in the emission of orange-red light. The optimum dopant concentration of Sm3+ion was 1 mol% and the main mechanism of concentration quenching was calculated using Dexter's theory. The bandgap of the undoped phosphor was found to be 5.31 eV. The CIE chromaticity coordinates are (0.56, 0.40) which confirms the orange-red emission. The obtained results indicate that the synthesized phosphor can be a potential candidate for application in solid-state lighting devices.

Downshifting and up-conversion luminescence of Yb3+-activated borotungstate Gd2(B2WO9) phosphor

Borotungstate phosphors Gd2–2xYb2x(B2WO9) (x=0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30) were synthesized using a straightforward high-temperature solid-state reaction method. The structural and luminescent properties of these phosphors were analyzed through X-ray powder diffraction, optical reflectance, excitation, and luminescence spectra. The up-conversion (UC) and downshifting (DS) processes, along with dynamic decay curves, were studied relative to the Yb3+ activator doping concentration. Upon near-UV excitation, a broadband near-IR luminescence (850–1150 nm) was observed from the 2F5/2→2F7/2 transitions in Yb3+ activators facilitated by significant energy transfer (ET) from the WO6 polyhedra to the Yb3+ activators within the lattices. Additionally, under 980 nm excitation to the 2F7/2 excitation states of Yb3+, blue cooperative up-conversion luminescence originating from Yb3+ pairs was detected. The mechanism behind this blue up-conversion was elucidated by analyzing decay lifetimes and emission intensity dependence on pump power, revealing that the cooperative de-excitation of adjacent Yb3+-Yb3+ ion pairs drives this process. This investigation introduces a practical approach for developing a novel Yb3+-doped borotungstate phosphor capable of exhibiting both downshifting and up-conversion luminescence.

Synthesis, crystal structure and luminescent properties of a quinary borate-phosphate compound CsNa2Dy2(BO3)(PO4)2

Abstract Borate-phosphates exhibit a wide range of compositional and structural diversity, making them ideal hosts for luminescent materials. In this work, a new borate-phosphate compound CsNa2Dy2(BO3)(PO4)2 has been prepared under high temperature solution growth method. It crystallizes in an orthorhombic space group Cmcm with the following lattice parameters determined by single-crystal X-ray diffraction: a = 6.9709(5), b = 14.9699(11), c = 10.6480(8) Å, z = 4. Its structure contains isolated BO3 planar triangles and PO4 tetrahedra, which are interconnected by Cs+, Na+ and Dy3+ ions. Solid solutions of CsNa2Y2(1−x)Dy2x (BO3)(PO4)2 (x = 0 − 0.08) are prepared and exhibit a yellow emissive luminescence by near-UV excitation due to the 4F9/2 → 6H(13/2, 15/2) transitions of Dy3+. The optimized concentration of Dy3+ is x = 0.01, and if over this critical value, the luminescent intensity will decrease due to concentration quenching. The Commission International de L’Eclairage (CIE) coordinates for CsNa2Y1.98Dy0.02(BO3)(PO4)2 are (x = 0.377, y = 0.404), corresponding to yellow color. The prepared phosphor may serve as a yellow phosphor for NUV-excited LEDs.

White light-emitting ZnO:Dy3+ nanophosphors: delving into the spectroscopic parameters via Judd-Ofelt analysis.

Developing a single-phase white emitting nanophosphor with high quantum efficiency has become a hotspot for scientific world. Herein, single-phase white-light emitting Zn1-xO:xDy3+ nanophosphors have been synthesized via a sonochemical method. X-ray diffraction analysis and Raman spectroscopy-based investigations confirmed the hexagonal wurtzite phase for Zn1-xO:xDy3+ nanophosphors with preferential growth along the (101) plane. Scanning electron microscopy images showed the formation of a ribbon-shaped morphology with a diameter of ∼25 nm. The emission spectra of the Dy3+-activated ZnO nanophosphors exhibited three distinct peaks, namely blue (480 nm), yellow (572 nm), and red (635 nm) emissions, under near-UV excitations related to the 4F9/2 → 6HJ (J = 15/2, 13/2, and 11/2) transitions of Dy3+ ions. The values of CIE chromaticity coordinates for the optimized phosphor (x = 0.329, y = 0.334) with correlated color temperature (CCT) of 5657 K indicated cool white-light emission from the phosphor. The thermal stability of ZnO:Dy3+ nanophosphors was probed by temperature-dependent luminescence. Quantitative evaluation of Judd-Ofelt intensity parameters, radiative parameters, luminescence decay, and quantum efficiency of Zn1-xO:xDy3+ using the J-O theory suggests that these nanophosphors are promising luminescent media for commercial white LEDs and other display devices.

Augmentation of the photoluminescence intensity via the incorporation of Eu3+ ions into single-phase Ba2La4Zn2O10 nanocrystalline material for advanced photonic applications

Strong red-emission is observed in the new Eu3+ activated Ba2La4Zn2O10 nanocrystalline material series fabricated via solution combustion methodology. A tetragonal crystal framework withspace group I4/mcm (140) having irregularly shaped grains with sizes between 33 and 62 nm is formed. Morphological aspects are examined via scanning and transmission electron microscopy (SEM and TEM). On near-UV excitation, the photoluminescence spectrum presents a fair red emission at 16129 cm−1 wavenumbers consistent with the electronic transition 5D0→7F2. The energy transfer phenomena are also discussed. The highest luminous intensity is observed for 5.0 mol% of Eu3+ composition with 394 nm excitation. d-d exchanges authorized the presence of the concentration quenching phenomenon. Diffuse reflectance spectroscopy was taken into use to explore the energy band gap which lies in the semiconductor domain. The CIE coordinates lay in the reddish zone of the chromaticity plot, thus confirming their latent contention in pc-WLEDs and other advanced photonic applications.

A new cyan phosphor NaAlO2:Bi3+ with high luminescent thermal stability

Developing new phosphors is an important issue for white LED applications. Herein, a simple compound NaAlO2 with an unusual compact 5-coordinated [NaO5] polyhedral environment is selected as host material. After doping Bi3+ into NaAlO2, Bi3+ may be occupy the Na-sites and interesting luminescent properties are expected. Experimental results show that phosphor NaAlO2:Bi3+ can emit cyan light under near-UV excitation. More exciting, the luminescent intensity of NaAlO2 is rather stable under high temperatures, which is due to the good structural rigidity of NaAlO2 host lattice and the process of trap-to-activator energy transfer. At 450 K, the typical working condition of LED devices, the PL intensity constitutes 92 % of the intensity at 300 K, which can guarantee its luminous efficiency for applications in LED devices. Finally, a white LED was fabricated by using a 365 nm LED ship, and a mixture of CaAlSiN3:Eu2+ (red phosphor), BaMgAl10O17:Eu2+ (blue phosphor) and NaAlO2:0.007Bi3+. The CIE coordinates, rendering index (Ra) and Correlated Color Temperature (CCT) of this lamp are (0.3183, 0.3307), 96.8 and 4429 K. This work confirms that the NaAlO2:Bi3+ material is a promising cyan phosphor for applications in LED field.

Excitation-Selective and Double-Emissive Lead-Free Binary Hybrid Metal Halides for White Light-Emitting Diode and X-Ray Scintillation.

Zero-dimensional (0D) organic metal halides comprising heterogeneous metal cations in single phase can achieve multiple luminous emissions enabling them toward multifunctional light-emitting applications. Herein, A novel single crystal of (C8H20N)4SbMnCl9 containing two luminescent centers of [SbCl5]2- pentahedrons and [MnCl4]2- tetrahedrons is reported. The large distance between Sb-Sb, Mn-Mn, and Sb-Mn as well as theory calculation indicate negligible interaction between individual centers, thus endowing (C8H20N)4SbMnCl9 with excitation-dependable and efficient luminescence. Under near-UV excitation, only orange emission originates from self-trapped excitons recombination in [SbCl5]2- pentahedron occurs with photoluminescence quantum yield (PLQY) of 91.5%. Under blue-light excitation, only green emission originating from 4T1-6A1 transition of Mn2+ in [MnCl4]2- tetrahedrons occurs with PLQY of 66.8%. Interestingly, upon X-ray illumination, both emissions can be fully achieved due to the high-energy photon absorption. Consequently, (C8H20N)4SbMnCl9 is employed as phosphors to fabricate white light-emitting diodes optically pumped by n-UV chip and blue-chip thanks to its excitation-dependable property. Moreover, it also shows promising performance as X-ray scintillator with low detection limit of 60.79 nGyair S-1, steady-state light yield ≈54% of commerical scintillaotr LuAG:Ce, high resolution of 13.5 lpmm-1 for X-ray imaging. This work presents a new structural design to fabricate 0D hybrids with multicolor emissions.

Novel low temperature synthesis of Y2-x 03 :Eux 3+ nanophosphor prepared by combustion with Thioglycerol as fuel for near UV light emitting diodes (n-UVLEDs).

Luminescent materials used in flat panel displays (FPD), compact fluorescent lamps (CFL), and light-emitting diodes (LEDs) require high purity, uniform particle size, clean surfaces, spherical shape, and dense morphology to ensure long-term stability. Y2 O3 :Eu3+ is a widely studied red phosphor known for its characteristic photoluminescence emission at 613 nm with near-UV excitation at 392 nm. Many synthesis methods have been explored to achieve Y2 O3 :Eu3+ nanoparticles with exceptional purity, consistent phases, and uniform particle sizes. The goal is to obtain particles with pristine surfaces, spherical shape, and compact morphology. This study focuses on the low-temperature synthesis and photoluminescence investigation of Y2-x O3 :Eux 3+ nanophosphors prepared using combustion with thioglycerol as a fuel. The results are compared with Y2-x O3 :Eux 3+ red nanophosphors synthesized using wet chemical and nitrate combustion methods. The photoluminescence characteristics of the Y2-x O3 :Eux 3+ nanophosphors were analyzed using PL emission spectroscopy, XRD, and scanning electron microscopy (SEM). These findings highlight the advantageous properties of the synthesized nanophosphors, such as their suitability for solid-state lighting applications in the lamp industry as highly efficient red phosphors. The combination of high purity, uniform particle size, clean surfaces, spherical shape, and dense morphology contributes to their potential for long-term stability and reliable performance in lighting devices.

Lanthanide Coordination Polymers with Soft-Base Ditopic Bisthiazolate Ligands.

In order to prepare the first lanthanide coordination polymers (CPs) based on ditopic sulfide ligands, benzo[1,2-d:4,5-d']bisthiazole-2,6(3H,7H)-dithione (H2L) was used as a linker. The reactions of lanthanide silylamides Ln[N(SiMe3)2]3 (Ln = Nd, Gd, Er, and Yb) with H2L result in the formation of soluble dimethyl sulfoxide (DMSO) ionic salts [Ln(DMSO)8][L]1.5 [Ln = Nd (1), Gd (2), Er (3), and Yb (4)]. Due to the lack of coordination of anionic ligands, compounds 1, 3, and 4 do not show sensitized metal-centered photoluminescence (PL), while Gd compound 2 shows weak phosphorescence at 77 K. It was found that the heating of 1 in a 1:9 DMSO/1,4-dioxane mixture leads to the formation of large crystals of 2D CP [Nd(DMSO)3L1.5·0.5diox]n (5), where deprotonated dithione H2L plays the role of a ditopic linker. This linker acts as an "antenna" in compound 5, providing an intense near-infrared (NIR) PL of Nd3+ ion upon near-UV and blue-light excitation. The application of a synthetic protocol similar to that of compounds 2-4 led to the formation of amorphous compounds [Ln(DMSO)3L1.5·0.5diox]n [Ln = Gd (6), Er (7), and Yb (8)], whose PL properties significantly differ from those of the parental ionic salts. In the case of Yb polymer 8, the PL excitation spectra are shifted to the red region due to a low-energy ligand-to-metal charge-transfer state. The synthesized compounds 5-8 are the first examples of lanthanide CPs using soft-base ditopic linkers in their structures.

Improvement of Luminescence Properties of Eulytite Single-Phase White Emitting Ca3Bi (PO4)3: Ce3+/Dy3+ Phosphor.

To reduce the issue of tri-primary color reabsorption, a new approach for single-phase phosphors as light-emitting diodes (LEDs) has been recommended. The structures, morphology, photoluminescence, thermal stability, and luminescence mechanism of a variety of Ca3Bi (PO4)3 (CBPO): Ce3+/Dy3+ phosphors were investigated. XRD characterization showed that all CBPO samples were eulytite structures. Furthermore, the energy transfer process from Ce3+ to Dy3+ in CBPO is systematically investigated in this work, and the color of light can be adjusted by changing the ratio of doped ions. Under UV light, energy is transferred from Ce3+-Dy3+ mainly through quadrupole-quadrupole interactions in the CBPO host, and doping with different Dy3+ concentrations tunes the emission color from blue to white. The thermal stability of the CBPO: 0.04Ce3+, 0.08Dy3+ samples is outstanding, and the CIE coordinates of the samples after emission have little effect with temperature, while their emission intensity at 423 K is as strong as that at room temperature, reaching 90%. The above results indicate that this CBPO material has great potential as a white light phosphor under near-UV excitation at the optimized concentration of Ce3+ and Dy3+.

Structural, optical and Judd-Ofelt analyses of Gd2-xEuxSi2O7 nanocrystals for lighting applications

A series of Eu3+-doped silicate-based red light-emitting nanocrystalline materials is fabricated via the solution combustion technique. Triclinic crystalline powders with a P-1 space group are formed containing irregularly sized grains. Three-lifetime values indicates the presence of three different local environments surrounding the Eu3+ ion. Upon near-UV excitation, the photoluminescence (PL) spectrum shows a red emission owing to the electronic band at ∼612 nm, consistent with the electronic transition 5D0 → 7F2. The energy bandgap is probed using diffuse reflectance spectroscopy. The critical distance between adjacent Eu3+ ions was evaluated to be ∼18.70 Å and multipolar exchanges were found accountable for the concentration quenching. The obtained chromaticity coordinates fall in the red regime of the CIE (1931) triangle, which replicates the potency of designated nanomaterials in the design and architecture of R-G-B (red–green–blue) phosphor-based LEDs.

Sensitizing effect of Sm3+ ions on Eu3+ incorporated boro-tellurite glasses for tunable red emission

Sm3+, Eu3+ singly doped and Sm3+/Eu3+ co-doped tungsten sodium zinc boro-tellurite glasses were prepared by melt quenching technique and the optical properties of these glasses have been investigated thoroughly. Under the excitation at 394 nm the Eu3+ doped prepared glass shows global red emission at x = 0.648, y = 0.341 in CIE1931 chromaticity diagram which is close to commercially developed phosphor Y2O2S: Eu3+ (0.647, 0.343) under near-UV excitation. Upon excitation at 404 nm, the Sm3+/Eu3+ co-doped glasses exhibit all the emission peaks for Sm3+ as well as Eu3+ ions, while exciting at 464 nm does not show the same result. Emission quenching occurs beyond 0.5 mol% of Sm3+ ions concentration in the present co-doped glasses. The possibility of non-radiative energy transfer from Sm3+ ions to Eu3+ ions has been verified by Forster-Dexter theory. The analysis of the decay profile for the 4G5/2 energy level of Sm3+ ions in the co-doped glass using Inokuti-Hirayama model suggests that the interaction between Sm3+-Eu3+ ions may be dipole-dipole in nature. The efficiency (ηT(Sm→Eu)) and probability rate (PT(Sm→Eu)) of energy transfer from Sm3+ → Eu3+ have been evaluated as 0.08 and 167 s−1, respectively. The results obtained from the radiative analysis suggest that the prepared glasses could be potentially used as red and orange-red or tuning red emitting materials.

The photoluminescence and Judd-Ofelt investigations of UV, near-UV and blue excited highly pure red emitting BaWO4: Eu3+ phosphor for solid state lighting

The article explores the photoluminescence properties of UV, near-UV and blue excited BaWO4: Eu3+ red phosphors. The optical band gap narrowing is observed after adding Eu3+ ions. The excitation spectra exhibit a broad peak centred at 255 nm and several narrow peaks of Eu3+ ions at 362, 382, 395, 415 and 465 nm. The three peaks located at 255 (UV), 395 (near-UV) and 465 nm (blue) are the most intense and suitable for the excitation of the sample. The spectral profile of the emission spectra irradiated at 255, 395 and 465 nm are identical. The brightest emission is realized at 18 mol% doping of Eu3+ ions at 255 and 465 nm excitations. However, the optimum concentration is 16 mol% at 395 nm excitation. The phosphors emit highly pure red lights with color purity 98.192%, 97.794% and 98.693% for the optimised concentration under UV, near-UV and blue excitations of 255, 395 and 465 nm, respectively. The quantum efficiency of BaWO4: 16 mol% Eu3+ phosphor is calculated as∼48.234% at 395 nm excitation. The emission intensity parameters are calculated in view of the Judd-Ofelt theory. The spectroscopic parameters like radiative transition probability, radiative lifetime, branching ratio and stimulated emission cross-section are further evaluated from the three emission spectra recorded at 255, 395 and 465 nm excitations. The derived results advocate the use of synthesized material as a red phosphor in white-LED, laser and display devices.

White-light emission from yttrium iron garnet (YIG)

Single-phase phosphors that emit broadband white-light are needed for white-light-emitting diodes (wLEDs) to reach their full potential. However, it is challenging to achieve broad white-light emission from single-phase materials. Consequently, polycrystalline inorganic bulk compounds that emit white-light sans doping are rare. We report on broadband white-light emission from a well-known garnet compound, i.e., yttrium iron garnet (YIG), without activator-ion doping. Upon near-UV excitation at 370 nm, polycrystalline bulk YIG emits broadband white-light with (1931) Commission Internationale de L’Eclairage (CIE) coordinates as (0.28, 0.35) and correlated color temperature (CCT) as 8029 K. Variable excitation wavelengths ranging from 280 to 600 nm enable color-tunable emission as cyan-white-blue-green-yellow-orange-red, including near-white-light emission for a broad range of excitation from 325 to 390 nm. Moreover, a short lifetime (sub-nanosecond) is obtained, which is desirable for LED and other applications. We demonstrated the propriety of YIG as a single-phase converting phosphor for illumination by fabricating prototype wLEDs using commercial InGaN UV-LED chips (λ = 380 nm) for excitation. The CIE coordinates and CCT of prototype wLEDs were obtained as (0.34, 0.37) and 5284 K, respectively. We believe that the reported findings signify the great potential of YIG as a single-phase white-light-emitting phosphor for broadband emission, which offers a new perspective and a viable approach for the development of wLEDs.

Preparation and luminescence investigations of garnet-based Y2Ca2Ga3VO12:RE (RE = Eu3+, Sm3+, and Dy3+) phosphors

We report, for the first time, the preparation and luminescence investigations of the YCGVORE (RE = Eu3+, Sm3+, and Dy3+) phosphors. The efficient multicolor emissions at 592 nm (orange), 612 nm (red), and 577 nm (yellow) were obtained from YCGVO:RE (RE = Eu3+, Sm3+, and Dy3+) phosphors with near-UV excitation. The room temperature decay of 5D0 (Eu3+), 4G5/2 (Sm3+), and 4F9/2 (Dy3+) levels in YCGVO:RE phosphors exhibits the average lifetime of 2.59–2.89, 0.82–1.44, and 0.25–0.63 ms, respectively. Upon excitation of VO43- group, the emission intensity of the RE ions increases with increasing the dopant concentration, simultaneously, the intensity of 520 nm emission related to the VO43- group decreases, indicating an efficient VO43− → RE energy transfer (ET). The YCGVO: RE (RE = Eu3+, Sm3+, and Dy3+) phosphors are promising candidate for white LED application.

Photoluminescence properties and energy transfer of Sr3Sc(BO3)3: Eu3+, Bi3+ phosphors

A number of orange-red Sr3Sc(BO3)3 phosphors with Eu3+ single-doping and Eu3+, Bi3+ co-doping were successfully made using the high-temperature solid-state method. The morphology and composition of the samples were examined using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), high-angle annular dark field (HAADF), and energy dispersive spectroscopy (EDS). Excitation and emission spectroscopy were used to investigate the characteristics of photoluminescence. In this work, Bi3+ are used as sensitizer to improve the emission intensity of Eu3+. The critical (or optimum) doping concentrations of Eu3+ and Bi3+ in Sr3Sc(BO3)3 were obtained experimentally (single-doping: 15 mol.% Eu3+, co-doping: 15 mol.% Eu3+, 0.3 mol.% Bi3+) to explore the energy transfer from Bi3+ to Eu3+. Under UV (393 nm) excitation, a strong orange-red luminescence corresponding to the 5D0→7F1 transition of Eu3+ can be observed, and a clear energy transfer from Bi3+ to Eu3+ can be discovered in the co-doped Sr3Sc(BO3)3. The energy transfer mechanism, as well as the CIE coordinates and decay lifetimes of a representative sample, are also discussed. The results show that Sr3Sc(BO3)3:Eu3+, Bi3+ is an orange-red phosphor with a higher efficiency under near-UV excitation.

Excellent thermostability and emission properties of Sr2CaTeO6:Sm3+ red emitting phosphor for high color-rendering white LEDs

A novel phosphor, red emitting Sr2CaTeO6:Sm3+ has been developed for white LEDs. The crystal structure and luminescence properties of this phosphor were investigated systematically. The space group of phase Sr2CaTeO6 compounds with a double-perovskite structure was found to be monoclinic P21/n (No.14). The Sr2CaTeO6:Sm3+ showed broad excitation band from 350 to 500 nm (monitored with emission wavelength at 648 nm), which is well aligned with 365 and 400 nm LED chips. Upon 407 nm near-UV excitation, the Sr2CaTeO6:Sm3+ exhibited red emission peak at about 658 nm. We found that Sr2CaTeO6:Sm3+ with 2 mol% of Sm3+ doping achieved the optimal performance. Meanwhile, the Sr2CaTeO6:Sm3+ phosphor showed good thermal stability. Finally, a near-UV pumped warm w-LED with the Sr2CaTeO6:Sm3+ phosphor, blue-emitting BAM:Eu2+ and green-emitting Lu-AG:Ce3+ phosphors was fabricated, which indicated that the Sr2CaTeO6:Sm3+ can be a promising red-emitting material for pc-LEDs.