Novel Emitting‐Color Tunable Phosphors Ba3Y2(BO3)4:Ce3+,Tb3+ with Efficient Energy Transfer for Near‐UV Light‐Emitting Diodes

This work presents the ultraviolet–visible spectroscopic properties of Ba₃Y₂(BO₃)₄:Ce³⁺,Tb³⁺ phosphors prepared by a high‐temperature solid‐state reaction. Under ultraviolet light excitation, tunable emission from the blue to yellowish‐green region was obtained by changing the doping concentration of Tb³⁺ when the content of Ce³⁺ is fixed. The efficient energy transfer process between Ce³⁺ and Tb³⁺ ions was observed and confirmed in terms of corresponding excitation and emission spectra. In addition, the energy transfer mechanism between Ce³⁺ and Tb³⁺ was proved to be dipole–dipole interaction in Ba₃Y₂(BO₃)₄:Ce³⁺,Tb³⁺ phosphor. By utilizing the principle of energy transfer and appropriate tuning of Ce³⁺/Tb³⁺ contents, Ba₃Y(BO₃)₄:Ce³⁺,Tb³⁺ phosphors can have potential application as an UV‐convertible phosphor for near‐UV excited white light‐emitting diodes.     

Tuning the Color Emission of Sr2P2O7: Tb3+, Eu3+ Phosphors Based on Energy Transfer

A series of color tunable Tb³⁺‐ and Eu³⁺‐activated Sr₂P₂O₇ phosphors were synthesized by a traditional solid‐state reaction method in air atmosphere. The crystal structure, photoluminescence (PL) properties, energy transfer, thermal stability, and luminous efficiency were investigated. A series of characteristic emission of Tb³⁺ and Eu³⁺ were observed in the PL spectra and the variation in the emission intensities of the three emission peaks at around 416 nm (blue), 545 nm (green), and 593 nm (orange‐red) induced the multicolor emission evolution by tuning the Tb³⁺/Eu³⁺ content ratio. The energy‐transfer mechanism from Tb³⁺ to Eu³⁺ ion was determined to be dipole–dipole interaction, and the energy‐transfer efficiency was about 90%. The novel phosphors have excellent thermal stability in the temperature range of 77–473 K and the Commission International De L'Eclairage 1931 chromaticity coordinates of Sr₂P₂O₇: Tb³⁺, Eu³⁺ (λ_ex = 378 nm) move toward the ideal white light coordinates.     

Preparation and Application of Strong Near‐Infrared Emission Phosphor Sr3SiO5:Ce3+,Al3+,Nd3+

This work investigated the near‐infrared (NIR) emission properties of mCe³⁺, xNd³⁺ codoped Sr_3?m?x(Si_1?m?xAl_m+x)O₅ phosphors. Samples with various doping concentrations were synthesized by the high‐temperature solid‐state reaction. Al³⁺ ions have the ability to promote Ce³⁺ ions to enter into the Sr²⁺ sites and to improve the visible emission of Ce³⁺. Thus the NIR emission of Nd³⁺ is enhanced by the energy‐transfer process, which occurred from Ce³⁺ to Nd³⁺. The device based on these NIR emission phosphors is fabricated and combined with a commercial c‐Si solar cell for performance testing. Short‐circuit current density of the solar cell is increased by 7.7%. Results of this work suggest that the Sr_2.95Si_0.95Al_0.05O₅:0.025Ce³⁺, 0.025Nd³⁺ phosphors can be used as spectral convertors to improve the efficiency of c‐Si solar cell.     

Temperature-sensing characteristics of NaGd(MoO4)2: Sm3+, Tb3+ phosphors

In this study, Sm³⁺/Tb³⁺-co-doped NaGd(MoO₄)₂ phosphors were prepared via the hydrothermal method, with sodium citrate used as a chelator. X-ray diffraction confirmed the structure of the samples, and the test outcomes showed that the phosphors exhibited a body-centered tetragonal structure. Field-emission scanning electron microscopy results showed that the specimen morphology changed with the change in the Cit^3?/Re³⁺ molar ratio. Moreover, the measured temperature-dependent emission spectra showed that Sm³⁺ and Tb³⁺ had different quenching trends; thus, the fluorescence intensity ratio can be used to represent temperature. In addition, the outcome of this experiment revealed that the temperature-sensing sensitivity of the phosphors gradually increased with the increasing Cit^3?/Re³⁺ ratio, and the highest sensitivity value was 0.346 K^?1 (at 503 K, Cit^3?/Re³⁺ = 2). When the temperature was 298–369 K, the temperature-sensing relative sensitivity increased with increasing Cit^3?/Re³⁺, but in the range 374–503 K, the relative sensitivity decreased with increasing Cit^3?/Re³⁺. The highest relative sensitivity value of the sample was 2.7% K^?1 (404 K, Cit^3?/Re³⁺ = 0). Additionally, the Commission International del’Eclairage chromaticity coordinates displayed that the luminous colors of Sm³⁺/Tb³⁺-co-doped specimens continuously changed from green to red as the temperature changed.     

Photoluminescence of Sr2P2O7:Sm3+ Phosphor as Reddish Orange Emission for White Light‐Emitting Diodes

A reddish orange emission Sr₂P₂O₇:Sm³⁺ phosphor is prepared by the solid‐state reaction method in air, and the crystal structure and luminescence properties of phosphors are investigated. Sr₂P₂O₇:Sm³⁺ phosphor shows Commission International de I'Eclairage (CIE) chromaticity coordinates (x = 0.5753, y = 0.4147). White light‐emitting diodes (W‐LEDs) fabricated using Sr₂P₂O₇:Sm³⁺ phosphor etc. show CIE chromaticity coordinates (x = 0.3471, y = 0.3124). These results indicate that Sr₂P₂O₇:Sm³⁺ phosphor could be a potential suitable reddish orange emitting phosphor candidate for W‐LEDs with excitation of a ~400 nm n‐UV LED chip.     

Luminescence Properties and Energy Transfer of Ce3+,Tb3+‐Coactivatedβ‐SiAlON Phosphors

Using the solid‐state reaction method, Ce³⁺,Tb³⁺‐coactivated Si₅AlON₇ (Si_6?zAl_zO_zN_8?z, z = 1) phosphors were successfully synthesized. The obtained phosphors exhibit high absorption and strong excitation bands in the wavelength range of 240–440 nm, matching well with the light emitting‐diode (LED) chip. The ET from Ce³⁺ to Tb³⁺ ions in Si₅AlON₇:Ce³⁺,Tb³⁺ has been studied and demonstrated by the luminescence spectra and decay curves. Moreover, the phosphors show tunable emissions from blue to green by tuning the relative ratio of the Ce³⁺ to Tb³⁺ ions. Thermal quenching properties of Si₅AlON₇:Ce³⁺,Tb³⁺ had also been investigated and the quenching temperature is ~190°C. These results show that Si₅AlON₇:Ce³⁺,Tb³⁺ could be a promising candidate for a single‐phased color‐tunable phosphor applied in UV‐chip pumped LEDs.     

Photoluminescence Properties of Color‐Tunable Ca3La6(SiO4)6: Ce3+, Tb3+ Phosphors

A series of newly developed color‐tunable Ca₃La₆(SiO₄)₆: Ce³⁺, Tb³⁺ phosphors were successfully prepared in this study. The crystal structures of the prepared phosphors were revealed to be hexagonal with space group P6₃/m, and the lattice parameters were evaluated via utilizing the Rietveld refinement method. Upon excitation at 288 nm, the emission spectra of Ce³⁺and Tb³⁺ ions co‐doped Ca₃La₆(SiO₄)₆ phosphors included a blue emission band and several emission lines. The blue emission band with a peak at 420 nm originated in the f–d transitions of Ce³⁺ ions, and the emission lines in the range of 450–650 nm were assigned to the ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions of Tb³⁺ ions. Increasing the doping content of Tb³⁺ ions considerably strengthened Tb³⁺ emission and reduced Ce³⁺ emission owing to the energy transfer from Ce³⁺ to Tb³⁺ ions. The mechanism of the energy transfer was confirmed to be a dipole–dipole interaction. The effective energy transfer from Ce³⁺ to Tb³⁺ ions caused a color shift from purplish‐blue to yellowish‐green. Color‐tunable Ca₃La₆(SiO₄)₆: Ce³⁺, Tb³⁺ phosphors have the potential to be utilized in light‐emitting diodes with proper modulation of the amount of Tb³⁺ ions.     

White‐emitting phosphor Ba2B2O5:Ce3+, Tb3+, Sm3+: Luminescence,energy transfer,and thermal stability

A series of Ba₂B₂O₅: RE (RE=Ce³⁺/Tb³⁺/Sm³⁺) phosphors were synthesized using high‐temperature solid‐state reaction. The X‐ray diffraction (XRD), luminescent properties, and decay lifetimes are utilized to characterize the properties of the phosphors. The obtained phosphors can emit blue, green, and orange‐red light when single‐doped Ce³⁺, Tb³⁺, and Sm³⁺. The energy can transfer from Ce³⁺ to Tb³⁺ and Tb³⁺ to Sm³⁺ in Ba₂B₂O₅, but not from Ce³⁺ to Sm³⁺ in Ce³⁺ and Sm³⁺ codoped in Ba₂B₂O₅. However, the energy can transfer from Ce³⁺ to Sm³⁺ through the bridge role of Tb³⁺. We obtain white emission based on energy transfer of Ce³⁺→Tb³⁺→Sm³⁺ ions. These results reveal that Ce³⁺/Tb³⁺/Sm³⁺ can interact with each other in Ba₂B₂O₅, and Ba₂B₂O₅ may be a potential candidate host for white‐light‐emitting phosphors.     

Visible Quantum Cutting and Energy Transfer in Tb3+‐Doped KSr(Gd,Y)(PO4)2 Under VUV–UV Excitation

KSr(Gd,Y)(PO₄)₂: Tb³⁺ phosphors were synthesized using the high‐temperature solid‐state reaction method. The VUV–UV spectroscopic properties of these phosphors were studied. The results show that efficient energy transfer (ET) from Gd³⁺ to Tb³⁺ occurs in this system, and the ET efficiency increases with increasing of Tb³⁺ doping concentrations, which is evidenced that both the emission intensity and decay time of Gd³⁺ decreases with increasing Tb³⁺ doping concentrations. Visible quantum cutting via cross relaxation between the neighboring Tb³⁺ ions was observed in the high Tb³⁺ concentration doped sample. In addition, the emission color of KSr(Gd,Y)(PO₄)₂: Tb³⁺ phosphors can be tuned from blue to yellowish‐green by varying the doping concentration of Tb³⁺. Under 147 nm excitation, the sample KSrGd_0.5(PO₄)₂: 0.5Tb³⁺ exhibits the strongest emission, which is about 70% of the commercial green‐emitting phosphor Zn₂SiO₄: Mn²⁺ indicating the potential application of this phosphor for plasma display panels, Hg‐free lamps, and three‐dimensional displays.     

Efficient Near‐Infrared Emission of Ce3+–Nd3+ CoDoped (Sr0.6Ca0.4)3(Al0.6Si0.4)O4.4F0.6 Phosphors for c‐Si Solar Cell

Ce³⁺, Nd³⁺ codoped (Sr_0.6Ca_0.4)₃(Al_0.6Si_0.4)O_4.4F_0.6 phosphors were synthesized through the high‐temperature solid‐state reaction method. Luminescence spectra, absorption spectra, and decay lifetimes of these samples have been measured to prove the energy‐transfer process from Ce³⁺ to Nd³⁺. Under UV and blue light excitation, (Sr_0.6Ca_0.4)₃(Al_0.6Si_0.4)O_4.4F_0.6:Ce³⁺,Nd³⁺ phosphors exhibit near‐infrared (NIR) emission, mainly peaking at 1093 nm and secondarily at 916 nm. The NIR emission matches well with the band gap of c‐Si. Results of this work suggest that the (Sr_0.6Ca_0.4)₃(Al_0.6Si_0.4)O_4.4F_0.6:Ce³⁺, Nd³⁺ phosphors have potential application as down‐shifting luminescent convertor for enhancing the photoelectric conversion efficiency of c‐Si solar cell.     

Effect of Tm3+ Ions on the White Light Emission of Dy3+–Tm3+ Codoped SrMg2La2W2O12 Phosphors

Dy³⁺–Tm³⁺ ions codoped SrMg₂La₂W₂O₁₂ (strontium magnesium lanthanum tungstate) phosphors were synthesized by conventional high‐temperature solid‐state reaction method. X‐ray analysis of the end products revealed the well‐crystallized phases with orthorhombic structure. The functional groups present in the phosphors were studied by the Fourier transform infrared measurements. To know the potential applicability of these phosphors for white light emission, the excitation and emission spectra were recorded. The excitation spectra exhibited an intense broad band at 313 nm, pertaining to the O → W ligand‐to‐metal charge‐transfer state (LMCT) of the host. With the excitation of LMCT band (313 nm), the decay curves of singly doped SrMg₂La₂W₂O₁₂:Dy phosphors exhibited single exponential, where as the codoped SrMg₂La₂W₂O₁₂:DyTm phosphors exhibited double exponential nature. The luminescence colors of these phosphors were estimated from Commission Internationale de L'Eclairage (CIE) coordinates using the photoluminescence data. The color of singly doped SrMg₂La₂W₂O₁₂:Dy phosphor has been tuned by codoping with Tm³⁺ ions. It has been noticed that the CIE chromaticity coordinates (x,y) determined from the luminescence spectrum of singly Dy³⁺ doped SrMg₂La₂W₂O₁₂ phosphor shifted toward the white light region, when codoped with Tm³⁺ ions. The increase in correlated color temperatures (T_cct) has been noticed with the increase of Tm³⁺ ions concentration in SrMg₂La₂W₂O₁₂:DyTm phosphors.     

Europium‐Activated KSrPO4–(Ba,Sr)2SiO4 Solid Solutions as Color‐Tunable Phosphors for Near‐UV Light‐Emitting Diode Applications

This article reports the structural and luminescence characteristics of Eu²⁺‐activated solid solutions of (KSrPO₄)_1?x·((Ba,Sr)₂SiO₄)_x for 0 ≤ x ≤ 1. These phosphors were prepared by a sol‐gel/Pechini method. The lattice parameters of the solid solutions are linearly dependent on x. The reliability factor from Rietveld analysis is nearly constant and independent of x, indicating KSrPO₄·(Ba,Sr)₂SiO₄ forms an ideal solid solution. The emission spectra consist of two distinct broad bands, which depend on x: blue ranging from 430 to 470 nm and green–yellow ranging from 515 to 570 nm. Both emission peaks red‐shift as x increases due to the crystal field effect and an anomalous transition. The emission intensity of these solid solutions is also a function of x and is comparable to that of LiCaPO₄:Eu²⁺ (QE = 81%) at x = 0.1, suggesting that these color‐tunable solid solutions are promising for applications in solid‐state white lighting.     

White light emitting from YVO4/Y2O3:Eu3+,Bi3+ composite phosphors for UV light-emitting diodes

A series of (1−x)YVO₄/xY₂O₃:Eu³⁺_0.006,Bi³⁺_0.006 (0≤x≤0.54) composite phosphors was synthesized in one step by high temperature solid state reaction and the photoluminescence properties were investigated. By means of co-doping Eu³⁺ and Bi³⁺ ions into the composite matrices composed of YVO₄ and Y₂O₃ crystals, the YVO₄/Y₂O₃:Eu³⁺,Bi³⁺ phosphor exhibits simultaneously the blue (418 nm), green (540 nm) and orange-red (595, 620 nm) emissions. The broad blue and green emissions are attributed to the ³P₁–¹S₀ transitions of Bi³⁺ ion both in Y₂O₃ and in YVO₄ matrices. Moreover, the sharp orange-red emissions are attributed to the ⁵D₀–⁷F_1,2 transitions of Eu³⁺ ion in YVO₄ matrix. By tuning the mole ratio of YVO₄/Y₂O₃ matrices the white light-emitting could be obtained. The results indicated that when the mole ratio of Y₂O₃ (x) is at 0.11–0.54 mol, the (1−x)YVO₄/xY₂O₃:Eu³⁺_0.006,Bi³⁺_0.006 phosphors emit white light by combining the blue, green and orange-red emissions under the excitation of 360–370 nm wavelength which matches the emission of the commercial UV-LED diode. This implies that the phosphors may be the promising white light materials with broad absorption band for white light-emitting diodes.     

Sr2SiO4:Sm3+红色荧光粉的发光特性

用高温固相法合成了Sr2SiO4:Sm3 红色荧光粉,并研究粉体的发光性质.发射光谱由位于红橙区的3个主要荧光发射峰组成,峰值分别位于570,606nm和653nm,对应了Sm3 的4G5/2→6H5/2,4G5/2→6H7/2和4G5/2→6H9/2特征跃迁发射,606nm的发射最强.激发光谱表现从350 nm到420nm的宽带,可以被近紫外光辐射二极管(near-ultraviolet light-emitting diodes,UVLED)管芯产生的350～410 nm辐射有效激发.研究了Sm3 掺杂和不同电荷补偿剂对样品发光亮度的影响,Sm3 掺杂摩尔分数为6%、电荷补偿剂为Cl-时的效果最好.Sr2SiO4:Sm3 是一种适用于白光LED的红色荧光粉.     

燃烧环境对铝酸锶铕镝激发发射光谱的影响

采用燃烧-发泡反应,于不同燃烧环境下,合成了不球磨的铝酸锶铕镝超细长余辉粉体材料。考察了点燃温度、燃烧体系、燃烧液与坩埚体积比、锶与尿素摩尔比以及盖子等因素对产物激发与发射光谱的影响。确定了最佳燃烧条件为:点燃温度600℃,硝酸盐-尿素体系,V(液体)/V(坩埚)=1/10,n(Sr)/n(尿素)=1/12,坩埚加盖。光谱分析表明,燃烧环境不同,产物的激发与发射峰强度不同;温度效应会使发射峰蓝移,压力效应会使发射峰红移,最大频移分别为16 nm和8 nm。     

Luminescence properties and energy transfer investigations of Sr2B2O5:Ce3+,Tb3+ phosphors

Ce³⁺ and Tb³⁺ co-doped Sr₂B₂O₅ phosphors were synthesized by the solid-state method. X-ray diffraction (XRD) was used to characterize the phase structure. The luminescent properties of Ce³⁺ and Tb³⁺ co-doped Sr₂B₂O₅ phosphors were investigated by using the photoluminescence emission, excitation spectra and reflectance spectra, respectively. The excitation spectra indicate that this phosphor can be effectively excited by near ultraviolet (n-UV) light of 317 nm. Under the excitation of 317 nm, Sr₂B₂O₅:Ce³⁺,Tb³⁺ phosphors exhibited blue emission corresponding to the f–d transition of Ce³⁺ ions and green emission bands corresponding to the f–f transition of Tb³⁺ ions, respectively. The Reflectance spectra of the Sr₂B₂O₅:Ce³⁺,Tb³⁺ phosphors are noted that combine with Ce³⁺ and Tb³⁺ ion absorptions. Effective energy transfer occurred from Ce³⁺ to Tb³⁺ in Sr₂B₂O₅ host due to the observed spectra overlap between the emission spectrum of Ce³⁺ ion and the excitation spectrum of Tb³⁺ ion. The energy transfer efficiency from Ce³⁺ ion to Tb³⁺ ion was also calculated to be 90%. The phosphor Sr₂B₂O₅:Ce³⁺,Tb³⁺ could be considered as one of double emission phosphor for n-UV excited white light emitting diodes.     

Enhanced Luminescence of Ca14Mg2Si8O28+δN4−δ:Eu2+Phosphors by Codoping Ce3+, Mn2+ for White LEDs and Their Energy‐Transfer Mechanism

The Eu²⁺, M‐codoped(M = Ce³⁺, Mn²⁺) phosphor powders were prepared by a solid‐state reaction. The addition of Ce³⁺ in the Eu²⁺ sites in partially nitridated bredigite‐structure phosphor(CMSN) remarkably enhances the luminescent intensity by ~180% through sensitized luminescence. Dual band emission was observed for Eu, Mn‐codoped CMSN through energy transfer from Eu²⁺ to Mn²⁺. Ce³⁺–Eu²⁺ and Eu²⁺–Mn²⁺ energy‐transfer mechanism was investigated through decay profile analysis using Inokuti–Hirayama model and energy‐transfer parameters are determined. Interaction mechanism was identified as dipole–dipole interaction. In addition, phosphor in glass plates was prepared using the phosphor and its feasibility in white LED application was studied and is presented.     

Photoluminescence Mechanism and Thermal Stability of Tb3+‐Doped Y4Si2O7N2 Green‐Emitting Phosphors

With solid‐state reaction method, series of Y₄Si₂O₇N₂:Tb³⁺ phosphors were prepared under the high‐temperature and high‐pressure conditions. The photoluminescence properties at room and high temperature were investigated. Two groups of emission lines have been observed, which are corresponding to Tb^{3+ 5}D₃ → ⁷F_J (J = 6, 5, 4, 3, 2) and ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions. The physical mechanisms for excitation, emission, concentration quenching, and thermal quenching were investigated. The cross‐relaxation mechanism between the ⁵D₃ and ⁵D₄ emission was investigated and discussed. The Tb–Tb critical distance for cross‐relaxation was calculated to be ~13 Å. The optimum Tb³⁺ concentration in this phosphor is 15 mol%. The quadrupole–quadrupole interaction dominates the non‐radiative energy transfer between the Tb³⁺ luminescence centers and causes the concentration quenching. This phosphor shows high thermal stabilities that at 150°C the intensity remains 92% compared with that measured at room temperature. The present work suggests that this Tb³⁺‐doped Y₄Si₂O₇N₂ material is a kind of potential green‐emitting phosphor.     

A Single‐Phase Phosphor NaLa9 (GeO4)6O2: Tm3+, Dy3+ for Near Ultraviolet‐White LED and Field‐Emission Display

Single‐phase white‐light‐emitting phosphors NaLa_9(1?x?y) (GeO₄)₆O₂: xTm³⁺, yDy³⁺ (NLGO: xTm³⁺, yDy³⁺) have been synthesized by a traditional solid‐state reaction method. The powder X‐ray diffraction (XRD), photoluminescence (PL), PL excitation (PLE) spectra, fluorescence decay curves, chromaticity coordinates, correlated color temperature (CCT), and the cathodoluminescence (CL) properties of the obtained phosphors are measured and discussed in detail. It is discovered that the series samples could be color‐tunable (from blue to yellow) by tuning the doping content of Dy³⁺ with a fixed Tm³⁺ content excited at 357 nm and white light (0.341, 0.324) could be obtained with the CCT of 5079 K. A NLGO: 0.01Tm³⁺, 0.02Dy³⁺ is studied carefully as representative. The main emissions of Tm³⁺ (453 nm, ¹D₂–³F₄) and Dy³⁺ (478 nm, ⁴F_9/2–⁶H_15/2; 572 nm, ⁴F_9/2–⁶H_13/2) make it emit white light with good thermal stability (67% of the initial till 523 K). The energy transfer from Tm³⁺ to Dy³⁺ is noticed and further research has been done to explain the enhancement of Dy³⁺ emission and the excellent thermal stability. It also keeps stable under continuous electron bombardment with high intensity. All of these indicate that it could be a suitable candidate for white‐emitting phosphor applied for near ultraviolet‐white light‐emitting diode (NUV‐WLED) and field‐emission display (FED).     

Na1.5Y2.5F9: Ce3+, Tb3+, Eu3+ glass-ceramics for white light

A simply encapsulated, long-range excitation method for white light generation was proposed. Na_1.5Y_2.5F₉: Ce³⁺, Tb³⁺, Eu³⁺ (NYFCTE) glass-ceramics (GCs) were synthesized by the melt-quenching method. The effect of crystallization temperature on the formation of crystallites was analyzed by X-ray diffraction (XRD). The morphology and size of nanocrystals were investigated by transmission electron microscope (TEM). The unit cell diagram of Na_1.5Y_2.5F₉ nanocrystals was drawn. In addition, the luminescence properties of Ce³⁺, Tb³⁺, Eu³⁺ ions-doped Na_1.5Y_2.5F₉ GCs were tested and analyzed. The sample NYFCTE2 emits bright white light when excited by a 320 nm light source at a distance from the light source. The NYFCTE2 sample obtained white light with Commission Internationale de L'Eclairage (CIE) coordinate of (0.3110, 0.3472), Correlated Color Temperature (CCT) of 6467.72 K, and reliable thermal stability. The above results indicate that the proposed white light generation method and NYFCTE GCs have immense application prospects for illumination.