Ca[B8O11(OH)4] : Eu2+ – A Highly Efficient Deep Blue-Emitting Phosphor Prepared by Low-Temperature Self-reduction

Highly efficient inorganic phosphors are crucial for solid-state lighting. In this paper, a new method of low-temperature self-reduction was used for preparing a highly efficient deep blue-emitting phosphor of Ca[B₈O₁₁(OH)₄] : Eu²⁺ (CBH : Eu²⁺). The crystal structure, morphology, chemical state, and photoluminescence (PL) properties of the CBH : Eu²⁺ phosphor have been investigated. By using the screened hybrid function (HSE06), the band gap (E_g) of CBH was calculated to be 7.48 eV, which is a necessary condition for achieving high quantum yield phosphors. The experiment results show that almost all the added raw materials of Eu³⁺ can be reduced to Eu²⁺ in CBH crystal under a non-reducing atmosphere. The CBH : Eu²⁺ phosphor shows a broad excitation spectrum centered at 277 and 327 nm in the range of 220 to 400 nm, and a narrow-band emission spectrum centered at 428 nm in the range of 400 to 500 nm, with a full width at half maximum (fwhm) of 42.35 nm. Under UV radiation, the CBH : 2 %Eu²⁺ exhibits high photoluminescence quantum yield (PLQY=95.0 %), high external quantum efficiency (EQE=31.1 %), and ultra-high color purity (97.6 %). The PL intensity of CBH : 2 %Eu²⁺ remains 62.6 % of the initial intensity at 150 °C. Finally, the white light-emitting diodes (WLED) fabricated by CBH : 2 %Eu²⁺, excited by a 365 nm chip, presents outstanding performances with a luminous efficacy (LE) of 13.9 lm/W, a color rendering index (CRI) of 89.4, and a correlated color temperature (CCT) of 5825 K. The above results show that CBH : Eu²⁺ can be used as a promising blue phosphor for WLED. This new method of low-temperature self-reduction can be applied to design and prepare other new types of highly efficient phosphors.     

Novel high-saturated red-emitting phosphor Sr9(Mg0.5Mn0.5)K(PO4)7: Eu2+ with great quantum efficiency enhancement by La3+ codoping for white LED application

In this work, a novel whitlockite-structure red-emitting phosphor host, Sr₉(Mg_0.5Mn_0.5)K(PO₄)₇, is designed and successfully synthesized via a solid-state reaction. Upon X-ray diffractometer Rietveld refinement, it is revealed that this compound possesses compact Eu²⁺-Mn²⁺ distance (3.6809 Å) and large intra-Mn²⁺ distance (8.9905 Å), which is beneficial to the high-efficient Eu²⁺-Mn²⁺ energy transfer. By Eu²⁺ sensitization, our new phosphor exhibits a high-saturated and bright red Mn²⁺ emission at 620 nm with high color purity of 97.9%. Great emission enhancement up to 245 times than host is achieved by La³⁺ heterovalent substitution, which can be ascribed to the La³⁺-induced further structural confinement effect. Moreover, the quantum efficiency is boosted by twofold. The as-fabricated white phosphor-converted LEDs device shows bright warm white light with correlated color temperature (CCT) of 3,487 K, color-rendering index (CRI) of 92.4, and luminous efficacy of 31.59 lm/W. This work proves the feasibility of chemical unit co-substitution strategy in emission engineering of Mn²⁺-based phosphors, which can stimulate further studies on the red-emitting phosphor materials.     

Obtain full visible spectrum light-emitting diode illumination via bismuth-activated cyan phosphors

Developing highly efficient cyan-emitting fluorescent materials is essential to bridge the cyan gap in phosphor-converted white light-emitting diodes for full-spectrum white illumination. Here, a Bi-doped cyan phosphor has been reported to solve this gap. The phase purity, photoluminescence emission/excitation spectra, concentration quenching, lifetime decay curves, and temperature-dependent photoluminescence emission spectra were systematically investigated. SrLaGaO₄:Bi³⁺ exhibits a broad excitation band (250–400 nm), which matches with the emission of a commercial near-ultraviolet light-emitting diode chip. The cyan light peaked at 475 nm is observed, which is attributed to the ³P₁→¹S₀ transition of Bi³⁺. The thermal quenching experiment was performed, and the activation energy was calculated as 0.36 eV. Finally, full-spectrum white light-emitting diode devices were fabricated using SrLaGaO₄:Bi³⁺ phosphors, commercial blue BaMgAl₁₀O₁₇:Eu²⁺ phosphor, green (Ba, Sr)₂SiO₄:Eu²⁺ phosphor, and red CaAlSiN₃:Eu²⁺ phosphor, which displayed an International Commission on an illumination coordinate of (0.3732, 0.3850), a correlated color temperature of 4290 K, and a color rendering index of 93.2 at a drive current of 20 mA. This result indicates that SrLaGaO₄:Bi³⁺ plays an essential role in bridging the cyan gap, providing new inspiration for applying cyan-emitting phosphors in full-spectrum white lighting.     

Tailoring of strong orange-red-emitting materials for luminescence lifetime thermometry,anti-counterfeiting,and solid-state lighting applications

Strong orange-red-emitting Ba₂LaTaO₆:Eu³⁺ phosphors were designed and applied in various optical applications of luminescence lifetime thermometer, anti-counterfeiting film, and solid-state lighting applications. The crystal structure, elemental composition, asymmetry ratio, and other luminescent behaviors were investigated in detail. Especially, the optimal Ba₂LaTaO₆:0.1Eu³⁺ phosphor presented remarkable quantum yield (45.29%) and thermal stability (71.52% at 423 K). Based on the temperature-dependent luminescence decay curves, the maximum relative sensing sensitivity was 0.185 × 10^?2 K^?1 at 513 K. In addition, a novel anti-counterfeiting technique was introduced. The fabricated polydimethylsiloxane films exhibited three different colors under the irradiations of room light, 254 nm light, and 365 nm light, respectively. Eventually, the packaged light-emitting diode displayed the pure orange-red emission. Briefly, a series of the Eu³⁺-activated Ba₂LaTaO₆ phosphors with excellent luminescent properties were characterized and further applied in several optical fields for the first time.     

Morphology control and luminescence properties of BaMgAl10O17:Eu phosphors prepared by spray pyrolysis

Starting from the aqueous solutions of metal nitrates with citric acid and polyethylene glycol (PEG) as additives, BaMgAl₁₀O₁₇:Eu²⁺ (BAM:Eu²⁺) phosphors were prepared by a two-step spray pyrolysis (SP) method. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra were used to characterize the resulted BAM:Eu²⁺ phosphors. The obtained BAM:Eu²⁺ phosphor particles have spherical shape, submicron size (0.5-3 μm). The effects of process conditions of the spray pyrolysis, such as molecular weight and concentration of PEG, on the morphology and luminescence properties of phosphor particles were investigated. Adequate amount of PEG was necessary for obtaining spherical particles, and the optimum emission intensity could be obtained when the concentration of PEG was 0.03 g/ml in the precursor solution. Moreover, the emission intensity of the phosphors increased with increasing of metal ion concentration in the solution. Compared with the BAM:Eu²⁺ phosphor prepared by citrate-gel method, spherical BAM:Eu²⁺ phosphor particles showed a higher emission intensity.     

Synthesis and luminescent properties of Eu2+ doped nitrogen-rich Ca-α-SiAlON phosphor for white light-emitting diodes

Yellow/orange-emitting nitrogen-rich Ca_0.9Si₉Al₃(O,N)₁₆: Eu²⁺ phosphors were successfully prepared by solid-state reaction synthesis. The fluorescence excitation spectra of all of the nitrogen-rich Ca_0.9Si₉Al₃(O,N)₁₆: Eu²⁺ phosphor powders displayed two broad bands centered at about 300 nm and 400–475 nm. The first peak was assigned to the absorption of the host lattice and the second to the 4f⁷ → 4f⁶5d¹ absorption of the Eu²⁺ ions, its means enhanced 4f⁷ → 4f⁶5d excitation of Eu²⁺ ion. The absorption peak intensity increased upon increasing the Eu²⁺ doping amount, but only up to a Eu²⁺ concentration ratio of 0.15. The emission spectra of the prepared Ca_0.9Si₉Al₃(O,N)₁₆: Eu²⁺ phosphors all exhibited a single broad band in the 500–700 nm region, maximum emission peak observed at 591 nm. The room temperature decay times were observed τ₁ = 1.27 μs and τ₂ = 9.90 μs.     

Synthesis and optical studies of novel Eu2+ and Ce3+ doped BaMg8Al18Si18O72 phosphors

Novel Eu²⁺ and Ce³⁺ activated BaMg₈Al₁₈Si₁₈O₇₂ phosphors was prepared by combustion method and their PL characteristics were investigated. The result shows that all samples can be excited efficiently by near UV excitation under 334 nm and 316 nm. The emission was observed for BaMg₈Al₁₈Si₁₈O₇₂:Eu²⁺ phosphor at 437 nm corresponding to d → f transition, under 334 nm broad-band excitation, whereas BaMg₈Al₁₈Si₁₈O₇₂:Ce³⁺ phosphor shows emission band at 376 nm under 316 nm excitation. Phase purity of the phosphor was checked with the help of XRD pattern. SEM analysis shows the external morphology of the combustion synthesized phosphor.     

Photoluminescence properties and application of yellow Ca0.65Si10Al2O0.7N15.3:xEu2+ phosphors for white LEDs

A series of yellow-emitting oxynitride Ca_0.65Si₁₀Al₂O_0.7N_15.3:xEu²⁺ phosphors with α-sialon structure were synthesized. The phase composition and crystal structure were identified by X-ray diffraction and the Rietveld refinement. The excitation and emission spectra, reflectance spectra and thermal stability were investigated in detail, respectively. Results show that Ca_0.65Si₁₀Al₂O_0.7N_15.3:0.12Eu²⁺ phosphors can be efficiently excited by UV-Vis light in the broad range of 290–450 nm and exhibit broad emission spectra peaking at 550–575 nm. The concentration quenching mechanism are discussed in detail and determined to be the dipole-dipole interaction. When the temperature increased to 150 °C, the emission intensity of Ca_0.65Si₁₀Al₂O_0.7N_15.3:0.12Eu²⁺ phosphor is 88.46% of the initial value at room temperature. White LED was fabricated with N-UV LED chip combined with blue Ca₃Si₂O₄N₂:Ce³⁺ and yellow Ca_0.65Si₁₀Al₂O_0.7N_15.3:Eu²⁺ phosphors. The color rendering index and correlated color temperature of this white LED were measured to 78.94 and 6728.12 K, respectively. All above results demonstrate that the as-prepared Ca_0.65Si₁₀Al₂O_0.7N_15.3:xEu²⁺ may serve as a potential yellow phosphor for N-UV w-LEDs.     

Mechanistic Insight into Energy-Transfer Dynamics and Color Tunability of Na4CaSi3O9:Tb3+,Eu3+ for Warm White LEDs

In this work, a latent energy-transfer process in traditional Eu³⁺,Tb³⁺-doped phosphors is proposed and a new class of Eu³⁺,Tb³⁺-doped Na₄CaSi₃O₉ (NCSO) phosphors is presented which is enabled by luminescence decay dynamics that optimize the electron-transfer energy process. Relative to other Eu³⁺,Tb³⁺-doped phosphors, the as-synthesized Eu³⁺,Tb³⁺-doped NCSO phosphors show improved large-scale tunable emission color from green to red upon UV excitation, controlled by the Tb³⁺/Eu³⁺ doping ratio. Detailed spectroscopic measurements in the vacuum ultraviolet (VUV)/UV/Vis region were used to determine the Eu³⁺–O²⁻ charge-transfer energy, 4f–5d transition energies, and the energies of 4f excited multiplets of Eu³⁺ and Tb³⁺ with different 4f^N electronic configurations. The Tb³⁺→Eu³⁺ energy-transfer pathway in the co-doped sample was systematically investigated, by employing luminescence decay dynamics analysis to elucidate the relevant energy-transfer mechanism in combination with the appropriate model simulation. To demonstrate their application potential, a prototype white-light-emitting diode (WLED) device was successfully fabricated by using the yellow luminescence NCSO:0.03Tb³⁺, 0.05Eu³⁺ phosphor with high thermal stability and a BaMgAl₁₀O₁₇:Eu²⁺ phosphor in combination with a near-UV chip. These findings open up a new avenue to realize and develop multifunctional high-performance phosphors by manipulating the energy-transfer process for practical applications.     

Synthesis and optical properties of novel red phosphors YNbTiO6:Eu3+ with highly enhanced brightness by Li+ doping

Highly luminescent euxenite phased YNbTiO₆:Eu³⁺ and Li⁺-doped YNbTiO₆:Eu³⁺ red phosphors have been prepared through a facile sol–gel combustion process and investigated for the first time. The introduction of Li⁺ ions into YNbTiO₆:Eu³⁺ is able to result in significant changes of the crystallinity and particle size, and bring a clear red-shift of absorption edge. A dominant red emission peak at 611 nm due to the ⁵D₀ → ⁷F₂ transition of Eu³⁺ was observed from photoluminescence spectra of the YNbTiO₆:Eu³⁺ and Li⁺-doped YNbTiO₆:Eu³⁺ phosphors. In particular, the emission intensity of the optimal Li⁺-doped YNbTiO₆:Eu³⁺ was examined to be close to 400% of commercial Y₂O₃:Eu³⁺ phosphor. The mechanism of the enhanced emission by Li⁺ doping was discussed.     

Optical characteristics of europium and terbium doped strontium orthogermanate phosphors

In this work, europium and terbium activated Sr₂GeO₄ phosphors were successfully developed by traditional solid state method. Powders XRD, FESEM, EDS, FTIR, DRS and PL techniques have been used to probe the as prepared phosphors. Powder XRD patterns of the phosphors are indexed. The elemental composition of phosphors was obtained from their EDS. FTIR spectra are employed to detect different vibrational groups in phosphor compositions. The DRS profiles of both pristine and Eu³⁺ (Tb³⁺) substituted samples exhibit broad and strong band in the 230–370 ​nm region. The photoluminescence studies of europium and terbium doped phosphors exhibited optimistic red emission at 617 ​nm (⁵D₀ → ⁷F₂ of Eu³⁺ ions) and intense green emission at 543 ​nm (⁵D₄ → ⁷F₅ of Tb³⁺ ions) upon ultraviolet (UV) excitations respectively. The CIE chromaticity co-ordinates are produced in deep red and green regions. Therefore, these materials may become potential alternatives for red and green phosphors in the display devices and in lamp industry.     

A near-infrared phosphor doped with Cr3+ towards zero-thermal-quenching for high-power LEDs

Cr³⁺-doped phosphors show significant application potential in near-infrared (NIR) light-emitting diodes (LEDs). However, the development of thermally stable and efficient NIR phosphors still faces enormous challenges. Herein, NIR phosphors K₂NaMF₆:Cr³⁺ (M³⁺ = Al³⁺, Ga³⁺, and In³⁺) were synthesized by the hydrothermal method. The represented K₂NaAlF₆:Cr³⁺ phosphor can be effectively excited by blue light (～430 nm) to present broadband emission at half a maximum of 96 nm peaking at ～ 728 nm. Meanwhile, the K₂NaAlF₆:Cr³⁺ phosphor exhibits excellent internal quantum efficiency (IQE = 68.08%) and nearly zero-thermal-quenching behavior, which is able to maintain 96.5% emission intensity at 150 °C of the initial value at 25 °C. The NIR phosphor-converted LED was fabricated based on K₂NaAlF₆:Cr³⁺ phosphor and a blue LED chip, showing a NIR output power of 394.39 mW at 300 mA with a high photoelectric conversion efficiency of 10.9% at 20 mA. Using the high-power NIR LED as a lighting source, transparent and quick veins imaging as well as non-destructive testing were demonstrated, suggesting the NIR phosphor has a wide range of practical applications.     

Tunable luminescence and energy transfer process between Tb3+ and Eu3+ in GYAG:Bi3+, Tb3+, Eu3+ phosphors

A series of Eu³⁺ ions co-doped (Gd_0.9Y_0.1)₃Al₅O₁₂:Bi³⁺, Tb³⁺ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of the GYAG:Bi³⁺, Tb³⁺, Eu³⁺ phosphors consists of broad bands in the shorter wavelength region due to 4f⁸ → 4f⁷5d¹ transition of Tb³⁺ ions overlapped with 6s² → 6s¹6p¹ (¹S₀ → ³P₁) transition of Bi³⁺ ions and the charge transfer band of Eu³⁺–O^2?. The present phosphors exhibit green and red colors due to ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions and ⁵D₀ → ⁷F₁ transition of Eu³⁺ ions, respectively. The emission was shifted from green to red color by co-doping with Eu³⁺ ions, which indicate that the energy transfer probability from Tb³⁺ to Eu³⁺ ions are dependent strongly on the concentration of Eu³⁺ ions.     

Luminescent properties of Sr<Subscript>3</Subscript>Al<Subscript>2</Subscript>O<Subscript>6</Subscript>: Eu,Pr prepared by sol–gel method

A new red-emitting long afterglow Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor was synthesized by sol–gel methods using Sr(NO₃)₂, Al(NO₃)₃·9H₂O, Eu(NO₃)₃ and Pr(NO₃)₃ as raw materials. The crystalline structure of the phosphor powders were characterized by X-ray diffraction. Luminescent properties of the phosphor powders were analyzed by the fluorescence spectrophotometer. Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor powders with single Sr₃Al₂O₆ phase were prepared at 1200 °C for 2 h in the reducing atmosphere. Pr³⁺ doped made the light intensity and the light-lasting time of Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphors improved. The emission peaks of the Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor powders lay at 612 nm with the excitation of 472 nm and the longest afterglow time could last for about 15 min at Pr³⁺ content of 0.06.     

微乳液法合成白光LED NaLu(MO4)2:Eu3+/Eu3+,Tb3+(M=W, Mo)荧光粉

采用微乳液法制备NaLu(WO₄)_2-x(MoO₄)x:8%Eu³⁺(x=0, 0.5, 1.0, 1.5, 2.0)/y%Eu³⁺,5%Tb³⁺(y=1, 3, 5, 7, 9)系列荧光粉.通过X射线衍射(XRD)表征,所制样品的X射线衍射峰与标准卡片PDF#27-0729基本吻合,表明所制的样品为白钨矿结构,属于四方晶系.扫描电镜SEM显示制备的纳米粒子是梭子状的,粒径大约是110 nm.激发发射光谱显示,在Eu³⁺离子掺杂浓度为8%时,NaLu(WO₄)(MoO₄):Eu³⁺发光强度最大.NaLu(WO₄)_2-x(MoO)x :8%Eu³⁺(x=0, 0.5, 1.0, 1.5, 2.0)荧光粉在Mo/W比达到1:1(x=1)时发光强度最大,强烈的红光发射表明该材料可用于白光LED材料.该荧光粉在268、394和466 nm波长光激发下分别发出橙红色、黄色和淡黄色光,可以满足不同光色需要.NaLu(WO)(MoO):y%Eu³⁺,5%Tb³⁺(y=1, 3, 5, 7, 9)荧光粉,随着y值增大,从绿光区(x=0.278, y=0.514)进入白光区(x=0.356, y=0.373), (x=0.278, y=0.313),同时观察到Tb³⁺到Eu³⁺有效能量传递.     

A new promising phosphor, Na3La2(BO3)3:Ln (Ln=Eu, Tb)

We present an efficient way to search a host for ultraviolet (UV) phosphor from UV nonlinear optical (NLO) materials. With the guidance, Na₃La₂(BO₃)₃ (NLBO), as a promising NLO material with a broad transparency range and high damage threshold, was adopted as a host material for the first time. The lanthanide ions (Tb³⁺ and Eu³⁺)-doped NLBO phosphors have been synthesized by solid-state reaction. Luminescent properties of the Ln-doped (Ln=Tb³⁺, Eu³⁺) sodium lanthanum borate were investigated under UV ray excitation. The emission spectrum was employed to probe the local environments of Eu³⁺ ions in NLBO crystal. For red phosphor, NLBO:Eu, the measured dominating emission peak was at 613 nm, which is attributed to ⁵D₀-⁷F₂ transition of Eu³⁺. The luminescence indicates that the local symmetry of Eu³⁺ in NLBO crystal lattice has no inversion center. Optimum Eu³⁺ concentration of NLBO:Eu³⁺ under UV excitation with 395 nm wavelength is about 30 mol%. The green phosphor, NLBO:Tb, showed bright green emission at 543 with 252 nm excited light. The measured concentration quenching curve demonstrated that the maximum concentration of Tb³⁺ in NLBO was about 20%. The luminescence mechanism of Ln-doped NLBO (Tb³⁺ and Eu³⁺) was analyzed. The relative high quenching concentration was also discussed.     

Enhancement of the photoluminescence and long afterglow properties of Ca<Subscript>2</Subscript>MgSi<Subscript>2</Subscript>O<Subscript>7</Subscript>:Eu<Superscript>2+</Superscript> phosphor by Dy<Superscript>3+</Superscript> co-doping

The Ca₂MgSi₂O₇:Eu²⁺ and Ca₂MgSi₂O₇:Eu²⁺, Dy³⁺ long afterglow phosphors were synthesized under a weak reducing atmosphere by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by powder X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) techniques. The luminescence properties were investigated using thermoluminescence (TL), photoluminescence (PL), long afterglow, mechanoluminescence (ML), and ML spectra techniques. The crystal structure of sintered phosphors was an akermanite type structure, which belongs to the tetragonal crystallography. TL properties of these phosphors were investigated, and the results were also compared. Under the ultraviolet excitation, the emission spectra of both prepared phosphors were composed of a broad band peaking at 535 nm, belonging to the broad emission band. When the Ca₂MgSi₂O₇:Eu²⁺ phosphor is co-doped with Dy³⁺, the PL, afterglow and ML intensity is strongly enhanced. The decay graph indicates that both the sintered phosphors contain fast decay and slow decay process. The ML intensities of Ca₂MgSi₂O₇:Eu²⁺ and Ca₂MgSi₂O₇:Eu²⁺, Dy³⁺ phosphors were proportionally increased with the increase of impact velocity, which suggests that this phosphor can be used as sensors to detect the stress of an object.     

Investigation of thermal decomposition of yttrium–aluminum-based precursors for YAG phosphors

Three types of precursors were prepared using the wet-chemical synthesis route, starting from yttrium?Ceuropium?Caluminum nitrate solution and different precipitating agents (urea, oxalic acid, and ammonium carbonate). The precursors were fired at 1200?°C in nitrogen atmosphere in order to obtain europium-doped yttrium aluminate Y₃Al₅O₁₂:Eu³⁺ phosphor with garnet structure (YAG:Eu). The processes involved in the thermal decomposition of precursors and their composition were put in evidence using thermal analysis (TG?CDTA) and FT-IR spectroscopy. The GA?CDTA curves possess typical features for basic-oxalate, -nitrate, and -carbonates as formed with oxalic acid, urea, and ammonium carbonate, respectively. Correlation between the thermal decomposition steps, mass loss, and composition of gases evolved during the thermal treatment was established using TG?CDTA?CFT-IR coupling. It was found that the different composition of precursors reflects on the luminescent characteristics of the corresponding phosphors. Urea and ammonium carbonate lead to the formation of YAG type phosphors, with garnet structure and specific red emission. As for the oxalic acid, this precipitating agent generates a non-homogeneous powder that contains yttrium oxide as impurity phase. This phosphor is a mixture of Y₂O₃:Eu³⁺, Y₄Al₂O₉:Eu³⁺, and Y₃Al₅O₁₂:Eu³⁺ that explain the relative higher emission intensity.     

High sensitivity and multicolor tunable optical thermometry in Bi3+/Eu3+ co-doped Ca2Sb2O7 phosphors

Currently, with increasing demand for non-contact fluorescence intensity ratio-based optical thermometry, a novel phosphor with high-efficiency, dual-emitting centers, and differentiable temperature sensitivity is more and more urgent to develop. In this work, an efficient dual-emitting center optical thermometry with high sensitivity and multicolor tunable in Ca₂Sb₂O₇:Bi³⁺, Eu³⁺ phosphor is firstly designed and successfully prepared. Under 330 nm excitation, the fabricated phosphor presents the featured and distinguishable emissions of Bi³⁺ and Eu³⁺ ions. The high efficiency energy transfer from Bi³⁺ to Eu³⁺ ions is proved and its corresponding mechanism belongs to dipole-dipole interaction. By modulating the ratio of Bi³⁺/Eu³⁺, the multicolor changes from blue to pink are realized. Based on the discriminative thermal quenching behavior between Bi³⁺ and Eu³⁺, the fluorescence intensity ratio of Eu³⁺ to Bi³⁺ in Ca₂Sb₂O₇ samples illustrates excellent optical thermometry performance from 298 to 523 K. The maximum absolute sensitivity (S_a) and relative sensitivity (S_r) reach as high as 0.2773 K^?1 at 523 K and 2.37% K^?1 at 448 K, respectively. Notably, the discriminated surrounding temperature can be directly confirmed by observing the emitting color from purple to orange-red with the temperature increase from 298 to 523 K. Furthermore, the as-prepared phosphor materials also demonstrate outstanding repeatability and excellent reversibility. These results exhibit that the designed Ca₂Sb₂O₇:Bi³⁺, Eu³⁺ phosphors have great promising applications in the field of non-contact optical temperature thermometry and thermochromic.     

微乳液法合成白光LED NaLu(MO_4)_2:Eu~(3+)/Eu~(3+),Tb~(3+)(M=W,Mo)荧光粉

采用微乳液法制备Na Lu(WO4)2-x(Mo O4)x∶8%Eu3+(x=0,0.5,1.0,1.5,2.0)/y%Eu3+,5%Tb3+(y=1,3,5,7,9)系列荧光粉。通过X射线衍射(XRD)表征,所制样品的X射线衍射峰与标准卡片PDF#27-0729基本吻合,表明所制的样品为白钨矿结构,属于四方晶系。扫描电镜(SEM)显示制备的纳米粒子是梭子状的,粒径大约是110 nm。激发发射光谱显示,在Eu3+离子掺杂物质的量分数为8%时,Na Lu(WO4)(Mo O4)∶Eu3+发光强度最大。Na Lu(WO4)2-x(Mo O4)x∶8%Eu3+(x=0,0.5,1.0,1.5,2.0)荧光粉在nMo/nW比达到1∶1(x=1)时发光强度最大,强烈的红光发射表明该材料可用于白光LED材料。该荧光粉在268、394和466 nm波长光激发下分别发出橙红色、黄色和淡黄色光,可以满足不同光色需要。Na Lu(WO4)(Mo O4)∶y%Eu3+,5%Tb3+(y=1,3,5,7,9)荧光粉,随着y值增大,从绿光区(x=0.278,y=0.514)进入白光区(x=0.356,y=0.373),(x=0.278,y=0.313),同时观察到Tb3+到Eu3+有效能量传递。