Variation in luminescence behavior of Yb3+ doped GdAlO3 phosphor with gradual increase in Yb3+ concentration

The present paper reports the combustion synthesis of Yb³⁺ doped GdAlO₃ phosphors. The structural characterization and luminescence spectra of Yb³⁺ doped GdAlO₃ phosphors have been discussed. The effects of variable concentration of Yb³⁺ on Photoluminescence (PL) behavior were studied. The structural characterization was done by X-ray diffraction (XRD) and Transmission electron microscope technique (TEM). The good connectivity with grains and the semi-sphere line structure was found by TEM. The functional group analysis was carried out by Fourier transform infrared (FTIR) spectroscopic techniques. The prepared phosphor gives emission spectra in visible as well as NIR region. Both emissions were studied as a function of Yb³⁺ concentration. The emission intensity variation with Yb³⁺ ion concentration for visible and NIR region were discussed separately. The NIR emission luminescence of GdAlO₃:Yb³⁺ phosphor luminescence continuously increases with increasing Yb³⁺ ion concentration.     

Energy transfer and luminescent properties of Ce, Cr co-doped Y3Al5O12

The phosphors in the system Y_3−xAl_5-yO₁₂:xCe³⁺,yCr³⁺ were synthesized by solid-state reactions and their photoluminescence properties were investigated. These phosphors have absorption in the visible light region and give luminescence in the far-red region (∼688 nm), which are suitable for the application in the device of luminescent solar concentrator (LSC). In these phosphors, Ce³⁺ located at Y³⁺ site can effectively transfer its absorbed energy to Cr³⁺ at Al³⁺ site.     

红色LiMBO3 : Re3+(Re=Eu,Sm) 发光材料的特性

采用固相法制备了红色LiM(M=Ca, Sr, Ba)BO₃ : Re³⁺(Re=Eu, Sm)发光材料,研究了材料的发光性能。研究发现LiM(M=Ca, Sr, Ba)BO₃ : Eu³⁺材料呈现多峰发射,最强发射分别位于610,615,613 nm处,分别监测这三个最强峰,所得激发光谱峰值位于369,400,470 nm。LiM(M=Ca, Sr, Ba)BO₃ : Sm³⁺材料也呈多峰发射,分别对应Sm³⁺的⁴G_5/2→⁶H_5/2、⁴G_5/2→⁶H_7/2和⁴G_5/2→⁶H_9/2跃迁发射;分别监测602,599,597 nm三个最强发射峰,所得激发光谱峰值位于374,405 nm。研究了激活剂浓度对材料发射强度的影响,结果随激活剂浓度的增大,发射强度先增强后减弱,即,存在浓度猝灭效应。实验表明,加入电荷补偿剂Li⁺、Na⁺或K⁺均可提高LiM(M=Ca, Sr, Ba)BO₃ : Re³⁺(Re=Eu, Sm)材料的发射强度。     

Photoluminescence and Optical Absorption of Cs2NaScF6:Cr3+

The main objective of this paper is the characterization of the spectroscopic properties of new materials that are prospective laser media. This approach allows for the comparison of the properties of the Cr³⁺ in different environments. Here, we have studied the photoluminescence and optical absorption of Cs₂NaScF₆:Cr³⁺ single crystals. On the basis of near-infrared luminescence measurements at 2, 77, and 300 K the observed lines originated from the Cr³⁺-centres were associated with the transition and the lifetimes were obtained. In spite of the quenching observed as a function of temperature at least 10% of the 2 K emission intensity for Cs₂NaScF₆ doped with 1% of Cr³⁺ remains at room temperature. Besides, the 2 K emission broad band could be well described in terms of normal modes of the octahedral complex [CrF₆]³⁻, and the Racah and crystal-field parameters calculated.     

Luminescent properties of Eu3+ and Sm3+ activated M2SiO4 (M=Ba,Sr and Ca) red-emitting phosphors for WLEDs

Eu³⁺ and Sm³⁺ activated M₂SiO₄ (M=Ba, Sr and Ca) red-emitting phosphors were synthesized by a solid state reaction. The results of XRD and SEM measurements show that the samples are single phase and have irregular shape. The excitation and emission spectra indicate that these phosphors were effectively excited by ultraviolet (395 nm) and blue (466 nm) light and exhibited red performance. The charge compensator R⁺ (R⁺=Li⁺, Na⁺ and K⁺) injecting into the host efficiently enhanced the luminescence intensity of the M₂SiO₄: Eu³⁺ and M₂SiO₄: Sm³⁺ phosphors. The emission intensity of M₂SiO₄: Eu³⁺ and Sm³⁺ doping Li⁺ were higher than that of Na⁺ or K⁺.     

Cr4+在Al2O3多晶体中的光谱性能研究

采用传统无压烧结工艺制备Cr:Al₂O₃透明多晶陶瓷.测定了其退火前后的吸收光谱和荧光光谱，发现在Al₂O₃六配位的八面体结构中，Cr⁴⁺的荧光发射也处在1100—1600nm波段的红外区间，荧光发射峰位于1223nm附近，类似Cr⁴⁺在四面体中的发光行为.同时由于氧化铝晶格常数较小，晶体场强较强，使Cr⁴⁺:Al₂O_{3< 关键词： 4+')" href="#">Cr⁴⁺ 2}O₃透明陶瓷')" href="#">Cr:Al₂O₃透明陶瓷 光谱性质 八面体     

Eu activated M6AlP5O20 (M=Sr/Ba/Mg) novel red phosphors

Eu³⁺ activated M₆AlP₅O₂₀ (where M=Sr/Ba/Mg) phosphors prepared by combustion synthesis and the completion of the synthesis was confirm by XRD (X-ray diffraction) patterns. The surface morphology studied by scanning electron microscopy (SEM) and photoluminescence (PL) properties has been reported in this paper. The Eu³⁺ PL emission spectrum was observed in M₆AlP₅O₂₀ phosphors (where M=Sr/Ba/Mg) at 592 (orange) and 618 nm (red) region, the spectrum due to ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at mercury free excitation, respectively. Its considerable emission intensity under 350 nm excitations makes it possible candidate materials as red component of tricolor luminescence materials and for near ultra violet light emitting diode (n-UVLED) phosphors.     

Photoluminescence and cathodoluminescence properties of Tb3+ activated Sr3AlO4F emitting-color tunable phosphor

Tb³⁺-activated Sr₃AlO₄F phosphors were synthesized by a high-temperature solid-state reaction method. The investigation of photoluminescence and cathodoluminescence indicates that these phosphors can be effectively excited by ultraviolet light and low-voltage electron beam. The phosphors exhibit a tunable-green emission. The luminescence behaviors are explained by the site occupancy of Tb³⁺ ions in the host crystal and the cross-relaxation of ⁵D₃ to ⁵D₄ state.     

Vibrational Analysis of the Elpasolites Cs2NaAlF6 and Cs2NaGaF6 Doped with Cr3+ Ions by Fluorescence Spectroscopy

Interest in 3d transition metal impurities in ionic crystals has increased due to their important role in the laser activity of these materials. Moreover, recent advances in tunable solid-state lasers and high-power semiconductor laser diode arrays have generated a strong interest in investigating new compounds that emit in the visible and near-infrared spectral regions. In particular, many optical studies have been devoted to Cr³⁺-doped fluoride crystals as a consequence of the high quality of some Cr³⁺-based laser materials. In the present investigation, the low-temperature emission spectra of Cr³⁺ ions in the hexagonal elpasolites Cs₂NaAlF₆ and Cs₂NaGaF₆ have been measured. Each compound has two crystallographically inequivalent octahedral sites for the Al³⁺ and Ga³⁺ ions that can be occupied by Cr³⁺ ions. For both materials, the luminescence spectrum presents two zero-phonon lines accompanied by a well-defined vibrational structure. The different peaks of the emission broad band are described in terms of phonons of the lattice and normal modes of the octahedral complex [CrF₆]^3–. A detailed analysis of the vibrational structure observed leads to the conclusion that the ² E and ⁴ T ₂ excited states of the [CrF₆]^3– ion are displaced along the e _g and a _1g and probably the t _2g coordinates.     

Luminescence of Cr ions associated with surpassing the green-emissive defect centers in β-Ga2O3

Photoluminescence of undoped and Cr³⁺-doped β-Ga₂O₃ was investigated. The transparent, undoped β-Ga₂O₃ film was successfully prepared by thermal conversion from GaOOH. The film exhibited predominant green luminescence in response to ultraviolet light excitation at 250 nm. This luminescence behavior, which was proposed to result from the oxygen defect centers, was used in examining excitation and emission mechanisms for Cr³⁺ ions doped in β-Ga₂O₃. It was found that red luminescence of Cr³⁺ surpasses green luminescence of the host lattice, as evidenced by the dependence of the spectral structure on the Cr³⁺ concentration. The excitation of Cr³⁺ was then suggested to be caused by the energy transfer from Ga³⁺O₆ octahedra present in the monoclinic β-Ga₂O₃ lattice.     

Photoluminescence properties of Li6CaB3O8.5: M3+ (M3+: Dy and Sm)

Li₆CaB₃O_8.5: M³⁺ (M³⁺: Dy and Sm) phosphors were synthesized by a solution combustion synthesis. The synthesized materials were characterized by using the powder XRD. The emission and excitation spectra of these materials were measured at room temperature with a spectrofluorometer. Both Li₆CaB₃O_8.5: Dy³⁺ and Li₆CaB₃O_8.5: Sm³⁺ phosphors emit red, yellow and green light. Consequently, these materials are promising phosphors for white LEDs.     

Emission analysis of Li6LuY(BO3)3:Tb3+,Dy3+ phosphors

In this paper, we present the synthesis and luminescence properties of Tb³⁺ and Dy³⁺-doped lithium lutetium yttrium borate (Li₆LuY(BO₃)₃) phosphors. We have adopted the well-known solid state reaction method for the synthesis of these phosphors. The emission intensities of the synthesized phosphors were found to reach their maximum, when doped by 1 mol% of Tb³⁺ and 3 mol% of Dy³⁺, beyond which emission intensities decrease due to concentration quenching. The homogeneous phase, crystalline structure and uniform morphology of the synthesized phosphors were confirmed by X-ray diffraction analysis (XRD) and Scanning electron microscopy (SEM). The X-ray and UV–VIS-induced luminescence, decay time and CIE chromaticity were investigated for the synthesized phosphors.The X-ray induced integrated light yield was measured to be 82% for Li₆LuY(BO₃)₃:Tb³⁺ (LLYBO) and 59% for Li₆LuY(BO₃)₃:Dy³⁺ of that of commercially available X-ray imaging material; Gd₂O₂S:Tb³⁺ (Gadox).LLYBO:Tb³⁺ phosphor displayed five major emission bands that correspond to ⁵D_j → ⁷F_j transitions. The 1931 Commission Internationale de l'Eclairage (CIE) chromaticity coordinates were also measured.     

Hydrothermal preparation and luminescence property of MWO4:Sm3+ (M = Ca,Sr, Ba) red phosphors

MWO₄:Sm³⁺ (M = Ca, Sr and Ba) red phosphors with spherical microparticles were successfully prepared via a mild and facile hydrothermal route. The crystal structure and particle morphology were investigated by the X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Photoluminescence excitation and emission spectra and decay curve were used to characterize the luminescence properties of the MWO₄:Sm³⁺ phosphors. The excitation spectra indicate that MWO₄:Sm³⁺ phosphors can be excited effectively by the UV InGaN light-emitting diode (LED), and the emission spectra show that the phosphors can emit strong red light from 600 to 650 nm. Therefore, it is considered to be a new promising red phosphor for white LED application.     

New aspects of the luminescence of magnesiumtitanate part I: Activation with chromium

Mg₂TiO₄:Cr³⁺ annealed at 560°C shows luminescence properties which differ considerably from those of the unannealed phosphor used so far. In both cases the regular Cr³⁺ ions only absorb the irradiated energy transferring it radiationless to the real luminescence centres, but the annealed phosphor reveals a new spectrum consisting of a few sharp lines. The radiance of the single lines can be influenced by powdering, which in connection with the annealing effect shows that the centres of both types of phosphors consist of clusters of lattice defects and octahedrally coordinated Cr³⁺ ions. These clusters or associates form themselves by thermal diffusion during the annealing process. Furthermore criteria have been found showing that the R lines do not come from only one but from two Cr³⁺ ions situated in non-equivalent lattice sites.     

Effect of Yb3+ concentration on photoluminescence properties of cubic Gd2O3 phosphor

Yb³⁺ doped phosphor of Gd₂O₃ (Gd₂O₃:Yb³⁺) have been prepared by solid state reaction method. The structure and the particle size have been determined by X-ray powder diffraction measurements. The average particle size of the phosphor is in between 35 and 50 nm. The particle size and structure of the phosphor was further confirmed by TEM analysis. The visible and NIR luminescence spectra were recorded under the 980 nm laser excitation. The visible upconversion luminescence of Yb³⁺ ion was due to cooperative luminescence and the presence of rare earth impurity ions. The cooperative upconversion and NIR luminescence spectra as a function of Yb³⁺ ion concentration were measured and the emission intensity variation with Yb³⁺ ion concentration was discussed. Yb³⁺ energy migration quenched the cooperative luminescence of Gd₂O₃:Yb³⁺ phosphor with doping level over 5%, while the NIR emission luminescence continuously increases with increasing Yb³⁺ ion concentration.     

New promising phosphors Ba3InB9O18 activated by Eu/Tb

Borate Ba₃InB₉O₁₈ (BIBO) has been adopted as a host material for phosphors for the first time. Lanthanide ions (Eu³⁺/Tb³⁺)-doped BIBO phosphors have been synthesized by solid-state reaction and luminescent properties investigated under ultravoilet (UV) excitation. For red phosphor BIBO:Eu, dominant emission peaking at 590 nm was attributed to ⁵D₀→⁷F₁ transition of Eu³⁺, which confirmed that the local site of Eu³⁺ occupied by In³⁺ ion in BIBO crystal lattice is at inversion symmetry center. Optimum Eu³⁺ concentration of BIBO:Eu under UV excitation with 227 nm wavelength is around 40%. The green phosphor BIBO:Tb showed bright green emission at 550 with 232 nm light excited and optimal of Tb³⁺ concentration measured in BIBO is about 8%. The corresponding luminescence mechanisms of Ln-doped BIBO (Ln=Eu³⁺/Tb³⁺) were analyzed. The luminescent intensity of Tb³⁺ can be significantly improved by co-doping of Bi³⁺ in the BIBO:Tb lattice. The likely reason was proposed in terms of the different interactions of the host lattice with these ions, and of these ions with each other.     

Luminescence characteristics of Eu2+ activated Ca2SiO4 Sr2SiO4 and Ba2SiO4 phosphorsfor white LEDs

<正>This paper investigates the luminescence characteristics of Eu²⁺ activated Ca₂SiO₄,Sr₂SiO₄ and Ba₂SiO₄ phosphors. Two emission bands are assigned to the f-d transitions of Eu²⁺ ions doped into two different cation sites in host lattices,and show different emission colour variation caused by substituting M²⁺ cations for smaller cations.This behaviour is discussed in terms of two competing factors of the crystal field strength and covalence.These phosphors with maximum excitation of around 370 nm can be applied as a colour-tunable phosphor for light-emitting diodes（LEDs） based on ultraviolet chip/phosphor technology.     

Photoluminescence investigations of Zn2SiO4 co-doped with Eu and Tb ions

Zinc silicate phosphors co-doped with Eu³⁺ ions and also with both Eu³⁺ and Tb³⁺ ions were prepared by high temperature solid state reaction in air or reducing atmosphere. The luminescence characteristics of the prepared phosphors were investigated. While in the samples prepared in air, Eu³⁺ emission was found to be dominant over Tb³⁺ emission, in the samples prepared in reducing atmosphere, intense Eu²⁺ emission at 448 nm was found to be predominant over narrow Tb³⁺ emission. Luminescence studies showed that Eu³⁺ ions occupy asymmetric sites in Zn₂SiO₄ lattice. The intense f-f absorption peak of Eu³⁺ at 395 nm observed in these phosphors suggests their potential as red emitting phosphors for near ultra-violet light emitting diodes.     

Sr和Ba替代对Eu掺杂Ca2.955Si2O7的结构和发光特性的影响研究

利用固相反应法制备了Sr和Ba替代的Ca_2.955-xM_xSi₂O₇: 0.045Eu²⁺ (M= Sr, Ba, x= 0.1-0.5)系列荧光粉, 利用较大离子半径的Sr和Ba元素替代Eu掺杂Ca_2.955-xM_xSi₂O₇ 中的Ca元素,研究Sr和Ba替代对样品结构和发光特性的影响. X射线衍射测试结果表明,少量Sr和Ba替代不会改变基质的晶体结构, 样品仍然为单斜晶系.未替代前, Ca_2.955Si₂O₇: 0.045Eu²⁺ 样品的发射峰在574 nm左右,随着Sr含量的增加,样品的发射峰发生蓝移; 而Ba含量在x= 0.1-0.4时不会引起发射峰位置的移动, 但x= 0.5样品的发射峰发生蓝移.同等含量的Sr和Ba部分替代样品中的Ca元素, Ba替代样品的光谱强度较强.     

Synthesis and characterization of novel red emitting nanocrystal Gd6WO12:Eu phosphors

Novel nanosized Gd₆WO₁₂:Eu³⁺ phosphors were synthesized via a co-precipitation reaction. The crystal structure and morphology of the phosphors were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). It was found that the resultant powders show a regular and sphere-like shape with average particle size of 60 nm. Intrinsic red emission originating from Eu³⁺ was observed while excited at the W⁶⁺→O²⁻ and Eu³⁺→O²⁻ charge transfer bands or f-f absorption bands. The color coordinates of the phosphors were calculated to be x=0.625, y=0.375. The concentration dependence of the luminescence was studied, and optimum doping concentration for obtaining maximum emitting intensity was confirmed to be around 12 mol%. It was also found that the electric dipole-dipole interaction plays an important role for quenching luminescence of Eu³⁺.