Luminescence properties and energy transfer in Ba2Y(BO3)2Cl:Ce3+,Tb3+ phosphors

Novel green-emitting Ba₂Y(BO₃)₂Cl:Ce³⁺,Tb³⁺ phosphors were synthesized by a solid-state method. X-ray diffraction and photoluminescence spectra were utilized to characterize the structures and luminescence properties of the as-synthesized phosphors, respectively. Ba₂Y(BO₃)₂Cl:Ce³⁺,Tb³⁺ phosphors exhibit blue and green emission bands under the excitation of near-ultraviolet light. An asymmetric blue emission originates from the Ce³⁺ ion, whereas the green emission originates from the Tb³⁺ ion. A spectral overlap is found between the emission band of the Ce³⁺ ion and the excitation band of the Tb³⁺ ion, which supports the occurrence of the energy transfer from the Ce³⁺ ion to the Tb³⁺ ion. Meanwhile, the energy transfer is thoroughly investigated by their photoluminescence decay behaviors. The energy-transfer efficiency from the Ce³⁺ ion to the Tb³⁺ ion is also calculated, and a possible mechanism is proposed.     

Luminescence properties and energy transfer investigations of BaAl2B2O7:Ce3+,Tb3+ phosphors

Ce³⁺ and Tb³⁺ co-doped BaAl₂B₂O₇ phosphors were synthesized by the solid-state method. X-ray diffraction (XRD) was used to characterize the phase structure. The photoluminescent properties of Ce³⁺ and Tb³⁺ co-doped BaAl₂B₂O₇ phosphors were investigated by using the photoluminescence emission and excitation spectra. Under the excitation of near ultraviolet (n-UV) light, BaAl₂B₂O₇: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. Effective energy transfer occurred from Ce³⁺ to Tb³⁺ in BaAl₂B₂O₇ 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 71%. Furthermore, the concentration quenching and critical distance of BaAl₂B₂O₇:Ce³⁺,Tb³⁺ phosphors were also discussed. The energy transfer from Ce³⁺ to Tb³⁺ in BaAl₂B₂O₇ host was demonstrated to be resonant type via a dipole–dipole interaction mechanism with the energy transfer critical distance of 16.13 Å.     

Luminescence and energy transfer of white-light emitting CaAl2SiO6:Ce3+, Tb3+ phosphors

A novel white-light emitting CaAl₂SiO₆: Ce³⁺, Tb³⁺ phosphor has been prepared by a sol–gel method. X-ray diffractometry and spectrofluorometry were used to characterize structural and optical properties of the samples. The results indicate that the crystal structure of the phosphor is a single phase of CaAl₂SiO₆. The excitation band of the phosphor covers a wide region from 240 nm to 380 nm. CaAl₂SiO₆: Ce³⁺, Tb³⁺ phosphors show four emission bands: one at 400 nm for Ce³⁺ and three at 487 nm, 543 nm and 585 nm for Tb³⁺. With appropriate tuning of Tb³⁺ content, white light with different hues can be achieved under UV radiation. The energy transfer mechanism from Ce³⁺ to Tb³⁺ in CaAl₂SiO₆ host was demonstrated to be dipole–dipole interaction.     

NaZnLa(PO4)2中Ce3+和Tb3+的发光

采用高温固相反应合成了NaZnLa(PO₄)₂中掺杂Ce³⁺、Tb³⁺的荧光体,对其晶体结构、发光行为进行了研究,并尝试对NaZnLa(PO₄)₂:Ce,Tb荧光体进行调制。NaZnLa(PO₄)₂是LaPO₄的同构物,为单斜晶系独居石结构,从XRD谱数据得到NaZnLa(PO₄)₂基质的晶胞参数为a=0.6823nm,b=0.7045nm,c=0.6497nm,β=1039°,v=0.303nm³,其晶胞参数与单斜LaPO₄的晶胞参数相似。在NaZnLa(PO₄)₂:Ce,Tb荧光体中,Ce³⁺对Tb³⁺有良好的敏化作用,掺杂适量的BO₃^3-、Al³⁺、Dy³⁺,可以增强发光亮度。     

KAlF4：Ce,Tb磷光体的发光特性及Ce^3＋对Tb^3＋的敏化作用

采用溶液反应法和高温固相反应法合成了ＫＡ１Ｆ４基质化合物及ＫＡ１Ｆ：Ｃｅ，Ｔｂ磷光体，测定了磷光体的激发光谱和发射光谱，研究了在碱金属氟铝酸盐基质中Ｃｅ＾３＋对Ｔｂ＾３＋的能量传递，根据Ｃｅ＾３＋，Ｔｂ＾３＋在ＫＡｌＦ４中的能级关系，分析了其发光特性和Ｃｅ＾３＋对Ｔｂ＾３＋能量传递过程。     

Photoluminescence and efficient energy transfer from Ce3+ to Tb3+ or Mn2+ in Ca9ZnLi(PO4)7 host

Structural and spectroscopic characterizations of the Ce³⁺/Tb³⁺(Mn²⁺) solely and Ce³⁺–Tb³⁺(Mn²⁺) doubly doped phosphate compound Ca₉ZnLi(PO₄)₇ with β-Ca₃(PO₄)₂ structure have been performed by powder X-ray diffraction and photoluminescence spectra measurements. The weak green emission from Tb³⁺ and red emission from Mn²⁺ are significantly enhanced by introduction of sensitizer Ce³⁺ ions due to an efficient resonant-type energy transfer from Ce³⁺ to activators Tb³⁺ or Mn²⁺. The energy transfer efficiency and the mechanism have been estimated based on spectroscopic data. Meanwhile, the critical distances for energy transfer between the Ce³⁺ and Tb³⁺ or Mn²⁺ ions are also calculated by the method of spectral overlapping.     

Luminescence properties and energy transfer in Eu2+, Mn2+ codoped Na(Sr,Ba)PO4 phosphor

Eu²⁺ and Mn²⁺ singly doped and codoped Na(Sr,Ba)PO₄ phosphors were synthesized, and their luminescent properties were investigated. A broad blue emission and a broad orange emission band were observed in Na(Sr,Ba)PO₄:Eu²⁺, Mn²⁺ phosphor. The resonant-type energy transfer from Eu²⁺ to Mn²⁺ was demonstrated, and the energy transfer efficiency was also calculated according to their emission spectra. Based on the principle of energy transfer, the emission intensity ration of Eu²⁺ and Mn²⁺ could be appropriately tuned by adjusting the contents of activators. Due to the strong absorption in the 250–400 nm range, Na(Sr,Ba)PO₄:Eu²⁺, Mn²⁺ phosphor could be used as a potential candidate for near-UV white light-emitting diodes (LEDs).     

Persistent luminescence properties of SrMg2(PO4)2:Eu2+,Tb3+

We investigate the persistent luminescence in europium-doped SrMg₂(PO₄)₂ upon codoping with auxiliary terbium. Luminescence properties of the phosphors, including photoluminescence, luminescence decay and thermoluminescence, are systematically studied. SrMg₂(PO₄)₂:Eu²⁺ shows only a weak persistent luminescence, and codoping with Tb³⁺ is necessary to obtain considerable persistent luminescence. An energy level scheme is constructed to convey reasonable trapping and detrapping processes in the material.     

Tb~(3+)和Ce~(3+)在Sr_7Zr(PO_4)_6基质中能量传递及发光特性研究

用高温固相法制备了Sr_7Zr(PO_4)_6∶Tb~(3+)、Sr_7Zr(PO_4)_6∶Ce~(3+)及Sr_7Zr(PO_4)_6∶Tb~(3+),Ce~(3+)一系列荧光粉,并通过X射线衍射仪及荧光光谱仪分析了其结构和发光性质。结果表明,Sr_7Zr(PO_4)_6∶Tb~(3+)呈现特征绿色发射,最强发射峰位于543 nm,属于Tb~(3+)的5D4→7F5跃迁,激发峰位于226 nm处,但激发带较窄。为拓宽其激发带的宽度,在Sr_7Zr(PO_4)_6∶Tb~(3+)中掺入了Ce~(3+),观察到掺入Ce~(3+)后激发带变宽,且在Ce~(3+)的激发波长处激发得到了Tb~(3+)的发射,表明存在Ce~(3+)到Tb~(3+)的能量传递。     

Luminescence properties of NaGd(PO3)4:Eu3+ and energy transfer from Gd3+ to Eu3+

The luminescence properties of polyphosphates NaEu _x Gd_(1?x)(PO₃)₄ (x = 0–1.00) and the energy transfer from Gd³⁺ to Eu³⁺ were studied. In undoped NaGd(PO₃)₄ sample, the photon cascade emission of Gd³⁺ was observed under ⁸S_7/2 → ⁶G_J excitation (201 nm) in which the emission of a red photon due to ⁶G_J → ⁶P_J transition is followed by an ultraviolet photon emission due to ⁶P_J → ⁸S_7/2 transition. When part of Gd³⁺ ions in the host NaGd(PO₃)₄ were substituted by Eu³⁺ ions, the NaGd(PO₃)₄:Eu³⁺ sample showed intensive red emission under 172-nm vacuum-ultraviolet (VUV) excitation which is suitable for mercury-free fluorescent lamps and plasma display panel applications. Based on the VUV–visible spectroscopic characteristics and the luminescence decay properties of NaGd(PO₃)₄:Eu³⁺, it was found that the quantum cutting by a two-step energy transfer from Gd³⁺ to Eu³⁺ can improve the red emission of Eu³⁺ ions under VUV excitation but only a part of the excitation energy in the excited ⁶P_J states within Gd³⁺ ions can be transferred to Eu³⁺ ions for its red emission, and the nonradiative energy transfer efficiencies from the excited ⁶P_J states within Gd³⁺ to Eu³⁺ were calculated.     

Photoluminescence properties of Ca9Lu(PO4)7:Ce3+, Mn2+ prepared by conventional solid-state reaction

A new red-emitting phosphor Ca₉Lu(PO₄)₇:Ce³⁺, Mn²⁺ has been synthesized by solid-state reaction, and its luminescence properties have been investigated. The broad red emission peaked at 645 nm of Mn²⁺ is greatly enhanced by the sensitizer Ce³⁺ due to efficient energy transfer from Ce³⁺ to Mn²⁺. The energy transfer was demonstrated to belong to a resonant type via a dipole–quadrupole mechanism. The critical distance for Ce³⁺→Mn²⁺ energy transfer was calculated to be 15.04 Å by concentration quenching method. Preliminary results indicate that the phosphor might be a promising red phosphor for UV-based white LEDs.     

KAIF4：Ce,Gd磷光体的荧光特性及能量传递

采用溶液反应和固相反应,分别合成了ＫＡＩＦ４基质化合物及ＫＡＩＦ４：Ｇｄ、ＫＡＩＦ４：Ｃｅ,Ｇｄ等磷光体,研究了它们的光谱特性。结果表明,ＫＡＩＦ４：Ｇｄ无认顷皮或长波紫外辐激发下,均无任何吸收和发射。在ＫＡＩＦ４：Ｃｅ,Ｇｄ中,Ｃｅ＾３＋离子能有效地将能量传递给Ｇｄ＾３＋离子,使Ｇｄ＾３＋产生了特征锐发射,具发射强度很大。但当Ｃｅ＾３＋浓度固定不变,改变Ｇｄ＾３＋的＾６Ｐ１／２→＾８Ｓ７／２发射     

Luminescence of impurity Ce3+ centers in KH2PO4 : Ce crystals

Physics of the Solid State - The photoluminescence, X-ray luminescence, and cathodoluminescence spectra of KH2PO4 : Ce single crystals contain a nonelementary band of radiation with an energy of...     

Study on the color tunability and energy transfer mechanism in Tb3+, Sm3+ co-doped LiLaSiO4 phosphors

A several of LiLaSiO₄: xTb³⁺, ySm³⁺ (LLSO) phosphors were synthesized by high-temperature solid-phase reaction. Through SEM, XRD and fluorescence spectrometer, the phase, morphology, luminescence properties and energy transfer of the samples were systematically analyzed and discussed. Under an excitation of 378 nm wavelength, LLSO: xTb³⁺ phosphors emit green light, and the concentration quenching point of Tb³⁺ ions was x = 0.08. In LLSO: xTb³⁺, ySm³⁺ phosphors, When Sm³⁺ ions doping molar mass fraction increases, the fluorescence intensity of Tb³⁺ ion decreases while the fluorescence intensity of Sm³⁺ ions first strengthen and then weaken. The concentration quenching point of Sm³⁺ ions was y = 0.04. By changing the proportion of Sm³⁺ and Tb³⁺ ions, the luminous color can be adjusted from green to red. There is effective energy transfer between Tb³⁺→Sm³⁺. The molar mass fraction of doping Sm³⁺ ions is y = 0.10, the energy transfer efficiency reaches 96.67%. The energy transfer mechanism is the quadrupole-quadrupole interaction. The quantum yield is 22.34%. Therefore, LLSO: xTb³⁺, ySm³⁺ phosphors have certain potential application value in the field of ultraviolet-near ultraviolet white LEDs.     

Luminescence and energy transfer in phosphor LiAl5O8: Ce3+, Dy3+

Ce³⁺ and Dy³⁺-doped LiAl₅O₈ were synthesized in the present study. The luminescence properties of Ce³⁺ and Dy³⁺, and the energy transfer from Ce³⁺ to Dy³⁺ were investigated. The Ce³⁺ species in LiAl₅O₈ emit one broad band that peaks at 351 nm under the excitation of ultraviolet light, which is attributed to the 5d–4f transitions of Ce³⁺. The luminescence of Dy³⁺ in singly doped LiAl₅O₈ can not be detected due to its low oscillator strength. However, Dy³⁺ emit intense blue (477 nm) and yellow (569 nm) light after the introduction of Ce³⁺. This phenomenon demonstrates that there exists effective energy transfer from Ce³⁺ to Dy³⁺, which occurs because the emission spectrum of Ce³⁺ perfectly overlays the excitation spectrum of Dy³⁺. The energy transfer from Ce³⁺ to Dy³⁺ is performed through dipole–dipole interactions. The experimental results show that LiAl₅O₈ co-doped with Ce³⁺ and Dy³⁺ can be a potential two-band (blue and yellow) phosphor.     

Energy transfer in CaSiO3 phosphors doped with Ce3+ and Tb3+

Calcium metasilicate phosphors activated by Ce³⁺ and Tb³⁺ have been studied for their emission characteristics. In two series of phosphors, one activator was kept at its optimum value while the other was varied. In another two series, one activator was kept below its optimum value and the other was varied. Concentration quenching effects start when each activator gives its maximum emission. There is clear evidence of an energy transfer from Ce³⁺ to Tb³⁺ because the⁵ D ₃ lines appear on addition of Ce³⁺ while they were conspicuously absent when Tb³⁺ alone was present. Their absence in singly activated phosphors could not have been due to cross-relaxation. Obviously X-ray excitation does not lead to⁵ D ₃ transitions which are achieved only by energy transfer. Further, considering the features of the emission spectra and the concentrations of activators used, the transfer could only be of the dipole-dipole type.     

Fluorescent properties of a blue-to green-emitting Ce3+, Tb3+ codoped amorphous calcium silicate phosphors

Ce³⁺, Tb³⁺ codoped amorphous calcium silicate phosphor was prepared by heating (830 °C for 30 min) Ce³⁺, Tb³⁺ codoped calcium silicate hydrate phosphor formed by liquid-phase reaction. The excitation peak wavelength of the resulting phosphor was 330 nm and the emission peak wavelengths were at 544 nm, attributed to the ⁵D₄→⁷F₅ transition of Tb³⁺, and at 430–470 mm, attributed to Ce³⁺. The intensity ratio of the two peaks could be freely controlled by varying the Tb/Ca atomic ratio of the Ce³⁺, Tb³⁺ codoped amorphous calcium silicate phosphor, allowing light to be emitted over a wide range from blue to green. It was clarified that energy transfer exists from Ce³⁺ to Tb³⁺.     

Y(BO3,PO4):Ce,Tb,Gd的发光特性研究

用ＢＰＯ４和稀土氧化为原料,通过单片灼烧,首次合成了铈、铽、钆共激活的硼磷钇绿色荧光粉,利用发射光谱和激发光谱研究了基质中Ｃｅ＾３＋、Ｔｂ＾３＋、Ｇｄ＾３＋的发光以及它们之间的相互作用结果表明在铈、铽或钆、铽的双掺杂体系中存在Ｃｅ＾３＋→Ｔｂ＾３＋、Ｇｄ＾３＋→Ｔｂ＾３＋的能量传递,而在铈、钆双掺杂的体系中却观察到了Ｃｅ＾３＋和Ｇｄ＾３＋离子之间的竞争吸收和独自发射。在铈、铽共激活的硼磷民体系中掺     

Ca8Mg(SiO4)4Cl2:Ce3+, Tb3+: A potential single-phased phosphor for white-light-emitting diodes

A single-phased white-light-emitting phosphor Ca₈Mg(SiO₄)₄Cl₂:Ce³⁺, Tb³⁺ (CMSC:Ce³⁺, Tb³⁺) is synthesized by a high temperature solid-state reaction method, and its photoluminescence properties are investigated. The obtained phosphor exhibits a strong excitation band between 250 and 410 nm, matching well with the dominant emission band of a UV light-emitting-diode (LED) chip. Energy transfer from Ce³⁺ to Tb³⁺ ions has been investigated and demonstrated to be a resonant type via a dipole–dipole mechanism. The energy transfer efficiency as well as the critical distance is also estimated. Furthermore, the phosphors can generate light from yellow-green through white and eventually to blue by properly tuning the relative ratio of Ce³⁺ to Tb³⁺ ions grounded on the principle of energy transfer. The results show that this phosphor has potential applications as a single-phased phosphor for UV white-light LEDs.