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Roles of crystal defects in the persistent luminescence of Eu^(2+), Dy^(3+) co-doped strontium aluminate based phosphors

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Rare Metals 2007年第4期26卷 305-310页

作者： LU Xingdong SHU Wangen School of Materials Jiangxi University of Finance and Economy Nanchang 330013 China College of Chemistry and Chemical Engineering Central South University Changsha 330013 China

The roles of different point defects in persistent luminescence of SrAl2O4：Eu,Dy phosphors were investigated. The research results showed that Dyer plays an important role in the persistent luminescence of SrA1EO4：Eu, Dy phosphors. It can serve as the electron trap of suitable depth for persistent luminescence. V~ does not serve as the electron trap of suitable depth, but its existence can increase the depth of electron traps. There is interaction between the Dy^3＋（ DySr ） and the Eu^2＋（Eu^x Sr ）, and only if the distance between the Dy^3＋（DySr） and the Eu^2＋（Eu^x Sr） is close enough, the Dyer can work as an effective electron trap. The point defect of V＂ Sr can be hole trap, but the change of its density in crystal matrix does not arouse the obvious change of persistent luminescence.

关键词： inorganic non-metal material strontium aluminate persistent luminescence rare earth ions point defect

Roles of Eu^(2+), Dy^(3+) Ions in Persistent Luminescence of strontium aluminates Phosphors

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Journal of Wuhan University of Technology(Materials Science) 2008年第5期23卷 652-657页

作者：吕兴栋 Academy of Functional Materials Jiangxi University of Finance and Economy

The polycrystalline Eu^2＋ and Dy ^3＋ co-doped strontium aluminates SrAl2O4： Eu^2＋, Dy^3＋ with different compositions were prepared by solid state reactions. The UV-excited photoluminescence, persistent luminescence and thermo-luminescence were studied and compared. Results show that the doped Eu^2＋ ion in SrAl2O4： Eu^2＋, Dy^3＋ phosphors works as not only the UV-excited luminescent center but also the persistent luminescent center. The doped Dy^3＋ ion can hardly yield any luminescence under UV-excitation, but effectively enhance the persistent luminescence and thermo-luminescence of SrAl2O4： Eu^2＋. Dy^3＋ co-doping can help form electron traps with appropriate depth due to its suitable electro-negativity, and increase the density and depth of electron traps. Based on above observations, a persistent luminescence mechanism, electron transfer model, is proposed and illustrated.

关键词： strontium aluminate persistent luminescence thermo-luminescence rare earthion

Electronic structure of the SrAl_2O_4:Eu^(2+) persistent luminescence material

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Journal of Rare Earths 2009年第4期27卷 550-554页

作者： Jorma Hls Taneli Laamanen Mika Lastusaari Janne Niittykoski Pavel Novák Department of Chemistry University of Turku FI-20014 Turku Finland Turku University Centre for Materials and Surface (MatSurf) Turku Finland Graduate School of Materials Research (GSMR) Turku Finland Institute of Physics Academy of Sciences of the Czech Republic CZ-16253 Prague 6 Czech Republic

The electronic structure of the strontium aluminate （SrAl2O4：Eu^2＋） materials was studied with a combined experimental and theo- retical approach. The UV-VUV synchrotron radiation was applied in the experimental study while the electronic structure of the non-optimized and optimized crystal structure were investigated theoretically by using the density functional theory. The structure of the valence and conduction bands as well as the band gap energy of the material together with the position of the Eu2＋ 4f7 85712 ground state were calculated. The calculated band gap energy （6.4 eV） agreed well with the experimental value of 6.6 eV. The valence band consisted mainly of oxygen states whereas the bottom of the conduction band of strontium states. In agreement with the experimental results, the calculated 4f7 8S7r2 ground state of Eu2＋ lies in the energy gap of the host. The position of the 4f7 ground state depended on the Coulomb repulsion strength. The position of the 4f7 ground state with respect to the valence and conduction bands was discussed using theoretical and experimental evidence available.

关键词： strontium aluminate persistent luminescence electronic structure DFT calculation rare earths

Effect of excitation wavelength(blue vs near UV)and dopant concentrations on afterglow and fast decay of persistent phosphor SrAl_(2)O_(4):Eu^(2+),Dy^(3+)

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Journal of Rare Earths 2022年第7期40卷 1022-1028页

作者： Bernhard Walfort Nando Gartmann Jafar Afshani Arnulf Rosspeintner Hans Hagemann LumiNova AG SwitzerlandSpeicherstrasse 60aCH-9053TeufenSwitzerland Dépt.de Chimie Physique Universitéde Genève30Quai E.AnsermetCH 1211Geneva 4Switzerland

The persistent phosphor SrAl_(2)O_(4):Eu^(2+),Dy^(3+)is the subject of numerous *** often neglected aspect is that in this phosphor,as well as in Sr_(4)Al_(14)O_(25):Eu^(2+),Dy^(3+),there are two different Sr^(2)+sites which can be occupied by the dopant Eu^(2+)ions,We first introduce a general scheme of possible energy transfers in these persistent phosphor materials including explicitly both europium ions,This scheme is used as a generic starting point to study experimentally specific *** illustrate this application with the study of the effect of excitation wavelength(444 and 382 nm)on the afterglow of differently doped SrAl_(2)O_(4):Eu^(2+),Dy^(3+)samples,as well as on the emission decay *** the same excitation intensity under 444 nm excitation,the resulting afterglow intensity is stronger than under near UV *** 382 nm,Eu^(2+)ions on both Sr^(2)+s ites in SrAl_(2)O_(4)are excited,but at room temperature the blue emission is quenched,leading to a loss of *** observed effects can further be associated with the ratio of Eu^(2+)ions and trap states which are modulated by the concentrations of Eu^(2+)and Dy^(3+)in SrAl_(2)O_(4),as well as by temperature,Increasing the nominal Dy^(3+)content from 0.1 mol%to 0.5 mol%with respect to Sr results in the doubling of the integrated afterglow intensity and confirms thus that Dy^(3+)ions are indeed involved in the trapping process,The concentration of trap states is much lower than the concentration of Eu^(2+)ions,as even with low excitation densities,a plateau of integrated afterglow intensity(corresponding to the total number of accessible traps)is *** postulate that an important fraction of excited Eu^(2+)ions can potentially transfer their energy to trap *** that all traps are filled or in a dynamical filling-depletion process under illumination(with thermal and/or optical depletion processes),for the remaining Eu^(2+)a"normal"steady-state emission is observed

关键词： Persistent phosphor strontium aluminate Europium Forster energy transfer Rare earths

Effects of transparent inorganic pigment on spectral properties of spectrum-fingerprint anti-counterfeiting fiber containing rare earths

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Journal of Rare Earths 2012年第9期30卷 952-957页

作者：张技术葛明桥 Key Laboratory of Eco-Textile Ministry of EducationCollege of Textiles and ClothingJiangnan University

Transparent inorganic pigment is the color-filler material for manufacturing spectrum-fingerprint anti-counterfeiting fiber, and has great effects on the emission spectral characteristics of the fiber. In order to explain the change mechanism of the emission spectral character- istics of spectrum-fingerprint anti-counterfeiting fiber and to promote the development of the fiber, several kinds of spectrum-fingerprint fiber samples were prepared by using rare-earth strontium aluminate and polyethylene terephthalate （PET） as raw materials and by adding different kinds of transparent inorganic pigments respectively in this research. The effect of transparent inorganic pigment on the spectral characteristics of the fiber was analyzed in detail by means of scanning electron microscopy （SEM）, X-ray diffraction （XRD） and fluorescence spectrometer. The results showed that transparent inorganic pigment had no effect on the dispersion state and phase structure of rare-earth luminescent mate- rial in spectrum-fingerprint fiber and the microscopic morphology of the fiber. However, transparent inorganic pigment did affect the excitation and emission process of spectrum-fingerprint fiber so as to decrease its excitation and emission efficiency. The change of both the type and content of transparent inorganic pigment exerted great effects on the excitation and emission spectra of the fiber. Therefore, it was a feasible way to control the emission spectrum of spectrum-fingerprint fiber through changing the type and content of transparent inorganic pigment.

关键词： luminescence pigments strontium aluminate fibers rare earths

Synthesis of Ultra-Fine SrAl_2O_4∶Eu, Dy Phosphor and Its Luminescent Properties

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Journal of Rare Earths 2004年第S1期22卷 71-75页

作者：吕兴栋舒万艮 College of Electronic Engineering Jiangxi University of Finance and Economics Nanchang 330013 China College of Chemistry and Chemical Engineering Central-South University Changsha 410083 China

Precursor of SrAl_2O_4∶Eu, Dy phosphor was prepared by co-precipitation method, in which dispersing agent was added to control particle size. Microwave radiation method was used to synthesize SrAl_2O_4∶Eu, Dy phosphors. Experimental results show that the precursor was composed of crystalline ammonium dawsonite hydrate and strontium carbonate, and the adding of dispersing agent can effectively diminish precursor size. The precursor can be transformed to pure SrAl_2O_4 phase after being calcined for 40 min in microwave chamber. The phosphors possess good persistent luminescent properties, finer grain size ranged from 0.2 μm to 5 μm and better size distribution than that of solid-state reaction. The doping of B^(3+) will result in the increasing of crystallite size, but can effectively improve phosphors′ persistent luminescent properties.

关键词： luminescent material co-precipitation microwave strontium aluminate afterglow rare earths

Preparation of Long Afterglow Photoluminescent Material SrAl_2O_4:Eu^(2+), Dy^(3+) and Its Luminescent Property

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Transactions of Tianjin University 2004年第3期10卷 201-205页

作者：徐明霞郭庆捷秦宇星 Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education School of Materials Science and Engineering Tianjin University Tianjin 300072 China

Long lasting strontium aluminate phosphors were synthesized by means of coated precipitation in the experiment. SrAl 2O 4 monoclinic phase with long afterglow was synthesized at 1 100 ℃ with the aid of H 3BO 3, and the synthetic temperature decreased about 100 ℃—150 ℃ than in solid state reaction. The process of heat treatment was studied by TG-DTA. The phase compositions of powders were analyzed by XRD. The micrographs of the samples were investigated by SEM and the luminescent properties were researched by optical spectrum. The effects of H 3BO 3 on the phase composition and microstructure of the calcined powders were investigated. The results indicated that H 3BO 3 accelerated the formation of SrAl 2O 4 by consuming the intermediate phase. The addition of Dy 2O 3 stimulated the afterglow property due to the increase in the depth of the trap center in the materials.

关键词： coated precipitation strontium aluminate boric acid phase conversion long persistent phosphorescence

Effects of Crystal Field on Long Phosphorescent Properties of SrAl2O4:Eu, Dy Phosphor

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Journal of Rare Earths 2006年第S2期 37-39页

作者：沈毅张平郑振太曲远方 School of Materials Science and Engineering Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education Tianjin University Tianjin 300072 ChinaHebei University of Technology Tianjin 300130 China Tianjin 300072 ChinaHebei Polytechnic University Tangshan 063009 China School of Materials Science and Engineering Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education Tianjin University

SrAl2O4∶Eu, Dy with Al/Sr ratio varying and Ba, Mg incorporation changing to a different crystal field was prepared by the combustion method to yield efficient luminescent phosphors. It is found that the ratio of Al to Sr strongly affects the emission spectra, as observed by fluorescence spectra. Based on XRD analysis, the effect of the ratio of Al to Sr on the host structure was discussed and an explanation on the color change was proposed. In addition, the effect of some alkali earth ions substituting in part for Sr2+ in strontium aluminate was investigated.

关键词： long afterglow phosphor combustion synthesis strontium aluminate crystal field rare earths

Luminescent Properties of SrAl2O4:Eu, Dy Material Prepared by Combustion Method

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Journal of Rare Earths 2006年第S2期 33-36页

作者：沈毅郑振太张平曲远方 School of Materials Science and Engineering Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education Tianjin University Tianjin 300072 ChinaHebei Polytechnic University Tangshan 063009 China School of Materials Science and Engineering Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education Tianjin University Tianjin 300072 ChinaHebei University of Technology Tianjin 300130 China

SrAl2O4∶Eu, Dy materials were prepared by the combustion of a mixture of the respective metal nitrates and urea at 500～700 ℃, over a time of 3～5 min, respectively. Compared with samples prepared by solid state reaction, the sintering temperature of combustion method is greatly reduced. The solid combustion products were identified by their characteristic X-ray powder diffraction patterns. A slight blue shift occurs in the excitation and emission spectra of the product prepared by the combustion method.

关键词： long afterglow phosphor combustion synthesis strontium aluminate crystal field rare earths