Europium-activated phosphor Ba3Lu2B6O15: Influence of isomorphic substitution on photoluminescence properties

This work demonstrates the luminescent properties of Ba₃Lu₂B₆O₁₅ phosphors doped with Eu³⁺ ions for the first time. The Ba₃(Lu_1–xEu_x)₂B₆O₁₅ (x = 0.01–0.375) phosphors have been prepared using a multi-step high-temperature solid-state synthesis. X-ray diffraction measurements verify the successful isomorphic substitution of the Lu³⁺ sites by the Eu³⁺ ions. The luminescence properties and its dependence on the crystal structure of Ba₃(Lu_1–xEu_x)₂B₆O₁₅ have been reported in this work. There are two nonequivalent sites in this crystal structures occupied by lutetium, both of them can be consistently substituted by the Eu³⁺ ions. The highest emission intensity with quantum yield of 17% was demonstrated by Ba₃(Lu_0.82Eu_0.18)₂B₆O₁₅ powder. Increase of Eu³⁺ doping concentration leads to gradual change of chromaticity from violet to red. It was expected that Ba₃(Lu_1–xEu_x)₂B₆O₁₅ phosphors can be used as a phosphor with predicted chromaticity under LED excitation.     

Structural and luminescent properties of Eu3+-doped double perovskite BaLaMgNbO6 phosphor

Eu³⁺-activated BaLaMgNbO₆ red-emitting phosphors were synthesized by a high-temperature solid-state reaction method. Phase analysis and luminescence were characterized by X-ray diffraction (XRD) and photoluminescence excitation and emission spectra. The XRD patterns showed that BaLaMgNbO₆ had a monoclinic structure with space group P21/n. The excitation spectra consisted of a broad charge-transfer band and some sharp f-f absorption peaks characteristic of Eu³⁺. The intensity ratio of I₆₁₅/I₅₉₀ was used to detect the chemical environment of Eu³⁺. The chromaticity coordinates of BaLa_0.7Eu_0.3MgNbO₆ were (0.67, 0.33), indicating that the BaLaMgNbO₆:Eu³⁺ phosphors were excellent red-emitting phosphors. Under excitation by near-ultraviolet (UV) and blue light, the phosphor not only exhibited intense red emission but also showed high color quality. The Ozawa and Dexter energy-transfer theories were employed to calculate the theoretical quenching concentration and determine the concentration quenching mechanism. In addition, the activation energy of BaLa_0.7Eu_0.3MgNbO₆ was calculated through the Arrhenius equation. A configurational coordinate diagram was used to explain the thermal quenching mechanism.     

Garnet-based red emitting phosphors Li6MLa2Nb2O12: Eu (M=Ca,Sr, Ba): Photoluminescence improvement by changing crystal lattice

A series of novel red emitting phosphors Li₆M(La_1−xEu_x)₂Nb₂O₁₂ (M=Ca, Sr, Ba; 0≤x≤0.3) were synthesized by solid state reaction, and their structures and photoluminescence properties were investigated in detail. The excitation spectrum of Li₆M(La_1−xEu_x)₂Nb₂O₁₂ revealed two mainly excitation bands at 393 nm and 464 nm, which match well with the two popular emissions from near-UV and blue LED chips. Upon the 464 nm light excitation, Li₆MLa₂Nb₂O₁₂:Eu³⁺ phosphors exhibit a red emission centered at 608 nm, originated from the ⁵D₀–⁷F₂ transition of Eu³⁺ ions. The Eu³⁺ surrounding crystal lattice environment in the garnet-based host was changed by altering the c sites element with different radii alkaline earth Ba, Sr, and Ca. The evident photoluminescence enhancement was observed in Li₆M(La_1−xEu_x)₂Nb₂O₁₂ phosphors with the decreasing of the c sites ionic radius. The emission intensity of the optimized Li₆Ca(La_0.8Eu_0.2)₂Nb₂O₁₂ (λ_exc=464 nm) phosphor is about two times higher than that of Y₂O₃:Eu³⁺ (λ_exc=467 nm) under blue light excitation. In addition, the quenching mechanism and the relationship between the structure and photoluminescence property were also discussed.     

VUV photoluminescence properties of Y1−xGdxVO4:Eu phosphors prepared by ultrasonic spray pyrolysis

The red-emitting (Y_1−xGd_x)_0.94Eu_0.06VO₄ (0 ≤ x ≤ 1.0) phosphors were synthesized by ultrasonic spray pyrolysis. The (Y_1−xGd_x)_0.94Eu_0.06VO₄ (0 ≤ x ≤ 1.0) phosphors had the tetragonal xenotime structure with a space group of I4₁/amd (1 4 1). The calculated crystallite sizes of the annealed phosphors ranged from 58 to 68 nm. In this study, we discussed the photoluminescence properties of the (Y_1−xGd_x)_0.94Eu_0.06VO₄ phosphors under VUV excitation, depending on Gd content. The emission intensity of the (Y_1−xGd_x)_0.94Eu_0.06VO₄ phosphors increased with increasing Gd content up to x = 0.5, and then decreased with a further increase in Gd content. The purest red color was obtained for the (Y_0.5Gd_0.5)_0.94Eu_0.06VO₄ phosphors.     

Tunable full color emission from single-phase LiSr3.99−xDy0.01(BO3)3:xEu3+ phosphors

Tunable full color emissive LiSr_3.99?xDy_0.01(BO₃)₃:xEu³⁺ (0≤x≤0.09) phosphors peaked at 481 nm (blue), 574 nm (yellow), 592 nm (orange), and 617 nm (red) were synthesized in air by high temperature solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), photoluminescence excitation (PLE) and photoluminescence (PL) spectra. The PLE spectra in the range from 200 to 500 nm include an Eu–O charge transfer band (CTB) and several 4f–4f transition peaks of Dy³⁺ and Eu³⁺, indicating its potential application in white light emitting diodes (LEDs). The effect of Eu³⁺ concentration on the emission intensity of LiSr_3.99?xDy_0.01(BO₃)₃:xEu³⁺ phosphors was investigated in detail and the optical concentration is found to be x=0.005. The CIE chromaticity coordinates for LiSr_3.99?xDy_0.01(BO₃)₃:xEu³⁺ phosphors are simulated. With an increase in Eu³⁺ ion concentration, the chromaticity color coordinates can be tuned efficiently from the border of greenish white region to its equal-energy white light point, and eventually to red region. All the results imply that the studied LiSr_3.99?xDy_0.01(BO₃)₃:xEu³⁺ phosphors could be potentially used as white LEDs.     

Effect of sintering atmosphere and lithium ion co-doping on photoluminescence properties of NaCaPO4:Eu phosphor

This paper reports on the photoluminescence properties of Na_1−yLi_yCa_1−xPO₄:_xEu²⁺ phosphors synthesized by a solid state reaction method. The prepared phosphors have been thoroughly characterized by means of X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectrum (FTIR), Raman spectrum, Thermo gravimetric and differential thermal analysis (TG–DTA) and photoluminescent spectral measurements. The structure of Na_1−yLi_yCa_1−xPO_4:xEu²⁺ phosphors were found to be orthorhombic in nature with a sphere-like morphology and having the particle size in micrometer range. The excitation spectra of NaCaPO₄:Eu²⁺ phosphors revealed a broad excitation band having its maximum intensity at 373 nm and ranging from 250 m to 450 nm. Incidentally, it matches well with the ultraviolet (UV) radiation of light-emitting diodes (LEDs). Upon 373 nm excitation, these phosphors exhibited intense bluish-green emission band centered at 505 nm. The effect of sintering atmospheres and co-doping of lithium ions on the photoluminescence properties of the NaCaPO₄:Eu²⁺ phosphors were studied and explained suitably. The obtained results indicate that the prepared NaCaPO₄:Eu²⁺ phosphors are promising bluish-green candidates for the phosphor-converted white LED applications.     

The doping concentration dependent tunable yellow luminescence of Sr5(PO4)2(SiO4):Eu

Color tunable yellow-emitting phosphors of Sr_5−5xEu_5x(PO₄)₂SiO₄ (x = 0.05-0.15) were prepared by conventional solid-state reaction method. The X-ray powder diffraction patterns, the photoluminescence excitation and emission spectra were measured. The main excitation bands of the phosphors locate at a broad band extending from 300 to 500 nm, which can match the emission of ultraviolet- and blue-emitting diode chips. The tunable luminescence color was realized by the changing Eu²⁺ doping in Sr₅(PO₄)₂SiO₄. The structure and luminescence properties were investigated. Sr_5−5x(PO₄)₂SiO₄:Eu_5x displays two typical luminescence centers, which originate from two different Sr²⁺ (Eu²⁺) sites in the host. The site-occupation, the luminescence intensity and energy transfer between the Eu²⁺ ions occupying two different crystallographic Sr²⁺ sites were discussed on the base of the luminescence spectra and crystal structure. This is helpful to improve this phosphor for a potential application as a white light emitting diode phosphor.     

Effect of Crystallite Size and Crystallinity on Photoluminescence Properties and Energy Transfer of Y6MoO12:Eu

The phosphors Y₆MoO₁₂:Eu³⁺ have been synthesized via citrate complexation method at different calcination temperatures. The evolutions of the crystal structure and the photoluminescence (PL) properties were characterized by means of powder X‐ray diffraction (XRD), Raman and PL spectra, respectively. It was revealed that a red emission could be obtained via three excitation channels, namely f–f transition of Eu³⁺ ions, charge‐transfer transition from O² to Eu³⁺, and interband transition (IBT) of MoO₆ groups. The PL spectra and their temporal decay character of Eu³⁺ ions depended on both crystal structure and excitation channel. The emission reduced with the crystallite size when Eu³⁺ ions were excited directly, but the emission evolved in a different model with the host lattices were excited. The effect of grain boundary and other lattice defect on the energy transfer and dissipation within the phosphors were discussed.     

Gel-combustion assisted synthesis of eulytite-type Sr3Y(PO4)3 as a single host for narrow-band Eu3+ and broad-band Eu2+ emissions

A series of eulytite-type Sr₃Y_1-x(PO₄)₃:xEu³⁺ (x = 0–0.13) and Sr_3-yY(PO₄)₃:yEu²⁺ (y = 0–0.10) phosphors were successfully synthesized via gel-combustion and subsequent calcination in O₂ and Ar/H₂ atmospheres at 1250 °C, respectively. Detailed crystal structure analysis via Rietveld refinement showed that the phosphors were crystallized in the cubic system (space group I-43d, No. 220), in which the Eu³⁺ and Eu²⁺ activators reside at the Y³⁺ and Sr²⁺ sites, respectively. The trivalent Eu³⁺ ions (CN = 6) exhibited typical narrow-band luminescence via intra-4f⁶ transitions, with the red emission at ~ 615 nm being dominant (⁵D₀ → ⁷F₂ transition, FWHM = 15.9 ± 0.2 nm). The divalent Eu²⁺ ions (CN = 6 and 9) showed broad-band luminescence ranging from light-blue to blue via 4f⁶5d¹ → 4f⁷ transitions (FWHM = 115 ± 2 nm). The optimal Eu³⁺ and Eu²⁺ concentrations were determined to be 10 at% (x = 0.10) and 7 at% (y = 0.07), respectively, and the mechanisms of concentration quenching were discussed. The excitation/emission properties, fluorescence decay kinetics, CIE chromaticity, and particularly the rarely addressed thermal stability of the phosphors were investigated in detail.     

A reddish orange stoichiometric phosphor LiEu(PO3)4 for white light-emitting diodes

Stoichiometric phosphors LiGd_1−xEu_x(PO₃)₄(x=0, 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized via traditional solid state reactions. The X-ray powder diffraction measurements show that all prepared samples are isostructural with LiNd(PO₃)₄. Eu³⁺ doped phosphors can emit intense reddish orange light under the excitation of near ultraviolet light from 370 to 410 nm. The strongest two at 591 and 613 nm can be attributed to the transitions from excited state ⁵D₀ to ground states ⁷F₁ and ⁷F₂, respectively. The typical chromaticity coordinates (x=0.620, y=0.368) of Eu³⁺ doped phosphors are in red area. The recorded absorbance spectra indicate that there is effective absorbance in the near UV region for all Eu³⁺ doped samples. Present research indicates that LiGd_1–xEu_x(PO₃)₄ is a promising phosphor for white light-emitting diodes.     

A novel scheelite-type LiCaGd(WO4)3:Eu3+ red phosphors with prominent thermal stability and high quantum efficiency

A series of LiCaGd(WO4)3 : xEu³⁺ (0 ≤ x ≤ 1.0) red phosphors with tetragonal scheelite structure were synthesized via the conventional solid-state reaction. Their crystal structure, photoluminescence excitation (PLE), and photoluminescence (PL) spectra, thermal stability and quantum efficiency were investigated. The phosphors exhibit a typical red light upon 395 nm near ultraviolet excitation, and the strongest emission peak at 617 nm is dominated by the ⁵D₀→⁷F₂ transition of Eu³⁺ ions. The PL intensity of the phosphors gradually increases with the increase of Eu³⁺ doping concentration, and the concentration quenching phenomenon is hardly observed. The quantum efficiency and the color purity of the phosphor reach maximum values of about 94.2 and 96.6% at x = 1.0, respectively. More importantly, LiCaGd(WO₄)₃:xEu³⁺ phosphors have prominent thermal stability. The temperature-dependent PL intensity of the phosphors at 423 K is only reduced to 89.1% of the PL intensity at 303 K, which is superior to that of commercial red phosphors Y₂O₃:Eu³⁺. Finally, LiCaGd(WO₄)₃:Eu³⁺ phosphor is packaged with near ultraviolet InGaN chips to fabricate white light emitting diodes, which has a low color temperature (CCT = 4622 K) and a high color rendering index (CRI= 89.6).     

Tunable luminescence properties and efficient energy transfer in Eu,Mn co-doped Ba2MgP4O13

A series of Ba₂Mg_1−xMn_xP₄O₁₃ (x = 0-1.0) and Ba_1.94Eu_0.06Mg_1−xMn_xP₄O₁₃ (x = 0-0.15) phosphors were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), the photoluminescence spectra, and the decay curves are investigated. XRD analysis shows that the maximum tolerable substitution of Mn²⁺ for Mg is about 50 mol% in Ba₂MgP₄O₁₃. Mn²⁺-singly doped Ba₂MgP₄O₁₃ shows weak red-luminescence peaked at about 615 nm. The Eu²⁺/Mn²⁺ co-doped phosphor emits two distinctive luminescence bands: a blue one centered at 430 nm originating from Eu²⁺ and a broad red-emitting one peaked at 615 nm from Mn²⁺ ions. The luminescence of Mn²⁺ ions can be greatly enhanced with the co-doping of Eu²⁺ in Ba₂MgP₄O₁₃. The efficient energy transfer from Eu²⁺ to Mn²⁺ is verified by the excitation and emission spectra together with the luminescence decay curves. The emission colors could be tuned from the blue to the red-purple and eventually to the deep red. The resonance-type energy transfer via a dipole-quadrupole interaction mechanism is supported by the decay lifetime data. The energy transfer efficiency and the critical distance are calculated and discussed. The temperature dependent luminescence spectra of the Eu²⁺/Mn²⁺ co-doped phosphor show a good thermal stability on quenching effect.     

Effect of Sr and Ca substitution of Ba on the photoluminescence properties of the Eu2+ activated Ba2MgSi2O7 phosphor

The effects of Sr and Ca substitution of Ba on the Ba_1.98-xSr_x(Ca_x)MgSi₂O₇:Eu²⁺ photoluminescence properties have been investigated. The physical mechanisms for the photoluminescence variations are discussed. With Rietveld refinement method, the crystal structure of Ba_1.98MgSi₂O₇:0.02Eu²⁺ and the lattice parameters of Sr and Ca substituted phosphors were refined. The emission band shift, the photoluminescence intensity variation, the phosphor chromaticity evolution, the Eu²⁺ lifetime distribution and the thermal stability elevation were investigated. With Sr and Ca substitution, the cell is shrinks. The cell shrinkage is resulting in the increase of the Eu²⁺ 5d electron crystal field splitting intensity, which is the reason for the emission band shift towards the long wavelength band. The photoluminescence intensity is increased firstly and then decreased. The intensity variation is the competitive result between the increase of the crystal structure rigidity and the rise of the lattice defect. The correlated color temperature can be cut down and the color purity can be adjusted. The photoluminescence life time of Eu²⁺ is raised firstly and then decreased. For Sr and Ca substitution, the thermal stability can be elevated. With the forbidden band gap calculation, the reason for the thermal stability elevation was investigated that for the substituted phosphors the forbidden band gap is enlarged and then limits the Eu²⁺ 5d self-ionization from the splitting levels to the conduction band. This work reveals that the Sr and Ca substitution of Ba can elevate the Ba_1.98-xSr_x(Ca_x)MgSi₂O₇:Eu²⁺ photoluminescence properties and improve the applications for the White Light Emitting Diode.     

Enhancement of oxygen/pressure sensing performance of Eu3+-doped YSZ phosphors via Bi3+ sensitization

The effects of the incorporation of a Bi³⁺ sensitizer on the phosphorescence properties and oxygen partial pressure sensitivity of the Eu³⁺ doped yttria stabilized zirconia (YSZ) phosphors were studied using a lifetime-based optical measurement system. Two series of YSZ: Eu phosphors were investigated in this work: Eu_0.01Bi_xY_0.07-xZr_0.92O_1.96 substitutional series and Eu_0.01Bi_xY_0.07Zr_0.92-xO_1.96-0.5x additive series. The phosphorescence intensity of the additive-series phosphors was enhanced by 47% excited at 405 nm with a Bi³⁺ concentration of 2 mol% due to the energy transfer between Bi³⁺ and Eu³⁺. In contrast, the phosphorescence intensity of the substitutional-series phosphors decreased as the Bi³⁺ concentration increased. The phosphorescence lifetimes for both series phosphors were highly sensitive to oxygen partial pressure at elevated temperatures. With increasing Bi³⁺ concentration, the oxygen sensitivities of both series were enhanced initially, which was related to the increment of concentration dependent non-radiative decay via cross-relaxation between Bi³⁺ and Eu³⁺. With 1 mol% Bi³⁺ doping, the oxygen sensitivity was enhanced by 28% and 12% for substitutional-series and additive-series phosphors, respectively. As the Bi³⁺ concentration further increased, the oxygen sensitivities of both series declined, which was attributed to the energy transfer between Bi³⁺, the formation of Bi³⁺ aggregates as well as the increase of the Eu³⁺ site symmetry. The results of this study not only provided valuable references for phosphor thermometry, but also offered new ideas for developing high-temperature non-contact pressure sensors.     

Enhanced luminescence of a Eu3+-activated double perovskite (Na,Li)LaMgWO6 phosphor based on A site inducing energy transfer

Li⁺ ion substituted Na_1−xLi_xLa_0.95Eu_0.05MgWO₆ phosphors were successfully synthesized by an improved sol-gel method using citric acid and polyethylene glycol as complexing agents. The structural evolution was systematically investigated by X-ray diffraction with Rietveld structure refinement and Raman spectra. The layered ordering of A-site cations and a second-order Jahn-Teller distortion of B’ cations simultaneously existed in this double perovskite. The decreased symmetry and lattice parameters within the same space group C2/m were observed from the Li⁺ substituted powders. Upon increasing the Li⁺ concentration, the absorption intensities of the 4f−4f transitions of Eu³⁺ monotonically increased. Likewise, the intensity of ⁵D₀-⁷F₂ monotonically increased under the excitations of both near-ultraviolet and blue light, with an enhancement of ten- and six-fold, respectively. The relative intensity ratio of red/orange emissions gradually increased, and the CIE chromaticity coordinates gradually approached those of standard red light. “A site inducing energy transfer” in double perovskite was achieved by selecting a substitution element with a small radius.     

Alkali metal ion substitution induced luminescence enhancement of NaLaMgWO6:Eu3+ red phosphor for white light-emitting diodes

Alkali metal ion substitution is an effective strategy to improve the luminescence properties of phosphors. In this work, a series of red-emitting phosphors Na_1-xLi_x/2K_x/2La_0.6Eu_0.4MgWO₆ were prepared by a traditional high-temperature solid-state reaction. Their phase structure, microstructure, luminescence properties and potential application in phosphor-converted white light-emitting diodes (pc-WLEDs) were investigated in detail. X-ray diffraction (XRD) result revealed the formation of a solid solution when x?≤?0.3, which kept monoclinic structure of NaLaMgWO₆. Photoluminescence investigation indicated that the partial substitution of Li⁺/K⁺ ions for Na⁺ ions improved largely the red emission of Eu³⁺. Based on the optimized Na_0.7Li_0.15K_0.15La_0.6Eu_0.4MgWO₆ sample with relatively good thermal stability, a WLED device was fabricated by combining a near-ultraviolet (NUV) chip (~400?nm) with the phosphor mixture of commercial green/blue phosphors and the optimized red phosphor. The results indicated that the optimized red phosphor in this work could be a potential candidate for WLEDs pumped by NUV chips.     

Synthesis and photoluminescence enhancement of Ca3Sr3(VO4)4:Eu3+ red phosphors by co-doping with La3+

In this study, a series of red-emitting Ca₃Sr₃(VO₄)₄:Eu³⁺ phosphors co-doped with La³⁺ was prepared using the combustion method. The microstructures, morphologies, and photoluminescence properties of the phosphors were investigated. All Ca₃Sr₃(VO₄)₄:Eu³⁺, La³⁺ samples synthesized at temperatures greater than 700 ℃ exhibited the same standard rhombohedral structure of Ca₃Sr₃(VO₄)₄. Furthermore, the Ca₃Sr₃(VO₄)₄:Eu³⁺, La³⁺ phosphor was effectively excited by near-ultraviolet light of 393 nm and blue light of 464 nm. The strong excitation peak at 464 nm corresponded to the ⁷F₀→⁵D₂ electron transition of Eu³⁺. The strong emission peak observed at 619 nm corresponded to the ⁵D₀→⁷F₂ electron transition of Eu³⁺. Co-doping with La³⁺ significantly improved the emission intensity of Ca₃Sr₃(VO₄)₄:Eu³⁺ red phosphors. The optimum luminescence of the phosphor was observed at Eu³⁺ and La³⁺ concentrations of 5% and 6%, respectively. Moreover, co-doping with La³⁺ also improved the fluorescence lifetime and thermal stability of the Ca₃Sr₃(VO₄)₄:Eu³⁺ phosphor. The CIE chromaticity coordinate of Ca₃Sr₃(VO₄)₄:0.05Eu³⁺, 0.06La³⁺ was closer to the NTSC standard for red phosphors than those of other commercial phosphors; moreover, it had greater color purity than that of all the samples tested. The red emission intensity of Ca₃Sr₃(VO₄)₄:0.05Eu³⁺, 0.06La³⁺ at 619 nm was ~1.53 times that of Ca₃Sr₃(VO₄)₄:0.05Eu³⁺ and 2.63 times that of SrS:Eu²⁺. The introduction of charge compensators could further increase the emission intensity of Ca₃Sr₃(VO₄)₄:Eu³⁺, La³⁺ red phosphors. The phosphors synthesized herein are promising red-emitting phosphors for applications in white light-emitting diodes under irradiation by blue chips.     

High luminescent brightness and thermal stability of red emitting Li3Ba2Y3(WO4)8:Eu3+ phosphor

A series of Li₃Ba₂Y_3−x(WO₄)₈:xEu³⁺ (x=0.1, 1, 1.5, 2 and 2.8) phosphors were synthesized by a high temperature solid-state reaction method. Under the excitation of near ultraviolet (NUV) light, the as-prepared phosphor exhibits intense red luminescence originating from the characteristic transitions of Eu³⁺ ions, which is 1.8 times as strong as the commercial Y₂O₂S:Eu³⁺ phosphor. The optimal doping concentration of Eu³⁺ ions here is confirmed as x=1.5. The electric dipole-quadrupole (D-Q) interaction is deduced to be responsible for concentration quenching of Eu³⁺ ions in the Li₃Ba₂Y₃(WO₄)₈ phosphor. The analysis of optical transition and Huang-Rhys factor reveals a weak electron-phonon coupling interaction. The temperature-dependent emission spectra also indicate that the as-prepared Li₃Ba₂Y₃(WO₄)₈:Eu³⁺ phosphor has better thermal stability than that of the commercial Y₂O₂S:Eu³⁺ phosphor. Therefore, our results show that the as-prepared Li₃Ba₂Y₃(WO₄)₈:Eu³⁺ phosphor is a promising candidate as red emitting component for white light emitting diodes (LEDs).     

Photoluminescence properties of NUV light excited Ba(Mg1/3Nb2/3)O3:Eu3+ red phosphor with high color purity

In this work, a new red phosphor with high color purity, Eu³⁺ ions doped Ba(Mg_1/3Nb_2/3)O₃ phosphor has been prepared by wet chemical method. The structure analysis suggests BMN:x%Eu phosphors have a hexagonal phase and Ba²⁺ ions are replaced by Eu³⁺ ions in BMN. Upon excitation of NUV light, the BMN:x%Eu phosphors emit strong red light around 615?nm, derived from the ⁵D₀-⁷F₂ transition of Eu³⁺ ions. The relationship between luminescent properties and structure of BMN:x%Eu was discussed. The Judd-Ofelt intensity parameters (Ω₂, Ω₄) were calculated to analyze the asymmetry of the Eu³⁺ ions site occupancy further, and the quantum efficiency of BMN:3%Eu was found to be 77.26%. In addition, the decay curve indicates the decay time(τ) of BMN:3%Eu is determined to be 1.34?ms and Eu³⁺ ions occupy only one type of site. The CIE chromaticity coordinate (0.656,0.344) of BMN:3%Eu is quite close to the red phosphors standard value (0.670, 0.330), which indicates BMN:x%Eu can be a suitable red phosphor used in NUV-based white LEDs.     

Overcoming the cyan gap for full-spectrum lighting using cation-substitution-induced rigid Ca2YZr2Al3O12:Ce3+

Mixing multicolor phosphors for simulating the full spectrum of sunlight illumination is a popular solution to obtain high-quality white light. However, there is still a need to overcome the cyan gap in the emission spectrum. In this work, a series of garnet Ca₂Y_0.94–xLu_xZr_2–yHf_yAl₃O₁₂:6%Ce³⁺ (abbreviated as CY_0.94–xLu_xZr_2–yHf_yA:Ce³⁺) cyan phosphors are designed and prepared by substituting Y³⁺ and Zr⁴⁺ in Ca₂YZr₂Al₃O₁₂:6%Ce³⁺ with Lu³⁺ and Hf⁴⁺ with smaller ionic radius and larger mass. Under 405 nm violet light excitation, the optimized Ca₂Y_0.88Lu_0.06Hf₂Al₃O₁₂:6%Ce³⁺ (CY_0.88Lu_0.06Hf₂A:Ce³⁺) shows a bright cyan emission band in the range of 430–750 nm with the peak at 477 nm. Importantly, the emission intensity and thermal stability properties of CY_0.88Lu_0.06Hf₂A:Ce³⁺ were significantly improved by 58% and 47% compared to those of pure Ca₂YZr₂Al₃O₁₂:Ce³⁺. Small and heavy cation substitution could induce highly stable rigid structure, thus enhancing emission intensity and stability. The color rendering index increases from 84.5 to 92.0 after supplementing CY_0.88Lu_0.06Hf₂A:Ce³⁺ phosphor in white light-emitting diode devices combining commercial red, green, and blue phosphors with a violet chip, indicating its practical application in full-spectrum lighting. The present study provides promising strategies for the design and development of efficient cyan materials for high-quality full visible spectrum light-emitting diode lighting.