DOCSLIB.ORG

Page 1 of 20 RSC Advances

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Page 1 of 20 RSC Advances RSC Advances This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. This Accepted Manuscript will be replaced by the edited, formatted and paginated article as soon as this is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/advances Page 1 of 20 RSC Advances Role of oxidizing agent to complete the synthesis of strontium aluminate based phosphors by the combustion method R.E. Rojas-Hernandez*, M.A. Rodriguez, J. F. Fernandez Electroceramic Department, Instituto de Cerámica y Vidrio, CSIC, Kelsen 5, 28049, Madrid, Spain. KEYWORDS: combustion synthesis; phosphorescence; nanostructure; sub-micron size; strontium aluminates Abstract The influence of processing parameters on phase formation of strontium aluminates doped with Eu2+ and Dy3+ by the combustion method has been evaluated. The addition of a slight excess of urea as fuel has an important effect on the phase formation, but a larger amount of urea inhibited the strontium incorporation into the stuffed tridymite-like structure. The experimental results show that it is possible to incorporate larger amount of urea than the theoretical one by adding nitric acid as oxidizing agent. The presence of an oxidizing agent Manuscript promotes both an effective chelation of the cations and a higher crystalline order on strontium aluminate. Nanostructured lamellar particles have been obtained in a single step and the particles are well crystallized. The combustion method avoids the standard requirements of post-thermal treatments in reducing atmosphere to promote the appearance of Eu2+ cations. A higher amount of urea in the presence of the oxidizing agent produces strontium aluminate particles with higher phosphorescence brightness, owing to the increase of the Accepted reduction process Eu3+ to Eu2+. The luminescence properties correlate with the crystallite size of the strontium aluminate. The results demonstrate a pathway to obtain phosphorescent pigments with size down to 10 µm. Advances RSC * Corresponding author. Tlf: +34 91 735 58 40; Ext 1074. Fax: +34 91 735 58 43. E-mail address:[email protected] (R.E. Rojas-Hernandez) RSC Advances Page 2 of 20 1. Introduction Phosphorescent materials have been studied due to their potential application in different areas like traffic safety and emergency signs, clocks, fluorescent devices and inks. After the discovery in 1996 of SrAl2O4: Eu2+Dy3+ as new persistent luminescent compound by Matsuzawa et al. [1], many researchers have developed some methods for preparation of strontium aluminate powders including sol-gel method, hydrothermal synthesis, chemical precipitation, solid-state reaction and so on. In recent years, rare earth-doped strontium aluminates have been intensively researched for their quantum efficiency, good stability, long-lasting time, which implies a wide application in many areas [1–3]. Commonly strontium aluminates are produced by solid state reaction, due to the refractoriness of alumina compounds; this method requires high temperatures, around 1300 – 1500ºC, and a long processing time. Some researchers included the addition of mineralizing agent as boron to decrease the synthesis temperature Manuscript [4,5], nevertheless, the powders produced by this synthesis route have a particle size within the range of 20 to 100 µm [6]; being a disadvantage for some applications. It is known that luminescent properties depend considerably on the grain size. New attractive applications will be possible if the grain size decreases down to 10 µm, particularly those related to printing technologies. Accepted 2+ 3+ Among the different synthesis methods, SrAl2O4: Eu Dy phosphors have been prepared by combustion method [7–9]. This method is suitable to obtain these functional materials due to some advantages such as low processing temperature and fast synthesis. In addition, this method produces a submicron grain size. For these reasons this synthesis method has been considered in order to obtain these phosphors. One of the advantages of the combustion method is the low temperature of synthesis. It has been reported that at Advances initiating temperature of 500ºC the SrAl2O4 a monoclinic phase begins to appear. Nonetheless, other references denote the optimal temperature should be 600ºC to achieve the best optical properties [10,11]. It is necessary to take into account that SrAl2O4 has two polymorphs: monoclinic symmetry that it is stable at RSC temperatures below 650ºC and hexagonal symmetry that it is stable above this temperature. Monoclinic phase shows the luminescent properties; however, there is not a clear agreement about the emission efficiency of the hexagonal structure in this system. Page 3 of 20 RSC Advances In the combustion method, the role of the fuel in the fulfillment of the synthesis has been investigated. Generally urea, CO(NH2)2, is the fuel used and some authors concluded that an excess urea should be required. The optimal quantity of urea is 1.5 times the theoretical one [10] considering that with low concentration of urea a complete reaction of raw materials it is not attained, while if the quantity is too high, the SrAl2O4 monoclinic structure does not synthesize. The maximum amount of urea it is limited to 2.5 times the theoretical one because the hexagonal phase becomes to appear when a higher quantity of urea are added [11]. The theoretical or stoichiometric amount of urea is calculated from the combustion reaction equation following this equation: 3Sr(NO3) 2 +6Al(NO3)3.9H20+ 20CO(NH2)2 →3SrAl 2O4 +94H2O +20CO2+32N2 (1) The incorporation of an excess of urea excess implies the contribution of other terms in the above equation Manuscript 3Sr(NO3)2 +6Al(NO3)3.9H20+ 20·m CO(NH2)2 +30(m-1)O2 → 3SrAl2O4 +(40·m +54) H2O (2) +20·m CO2+(20·m +12)N2 where m denotes the urea ratio. An excess of urea implies therefore a higher consumption of oxygen in order to complete the reaction. To optimize the combustion synthesis an oxidizing agent as nitric acid could be Accepted particularly relevant. 2+ 3+ Therefore, in this work different urea amount in the combustion synthesis of SrAl2O4: Eu Dy are used and it carried out a study related the effect of nitric acid incorporation. The use of oxidizing agent could improve the reaction completion as well to tailor phosphorescent properties. The correlation between combustion process, morphology and optical properties of strontium aluminate based particles is discussed. Advances RSC 2. Experimental details 2+ 3+ SrAl2O4: Eu , Dy particles were synthesized via solution combustion synthesis. The solution was prepared by dissolving Al(NO3)3⋅9H20 (Merck, 98.5%) in deionized water and SrCO3 ( Merck, 99.9%), Eu2O3 (Metal Rare Earth Limited, 99.5%) , Dy2O3 (Rare Earth Limited, 99.5%) in nitric acid HNO3 (Sigma-Aldrich, 65%) to form nitrate solution. The above materials were mixed according to the chemical formula Sr1-x- yEuxDyyAl2O4, where x = 0.02 and y= 0.01. During the 30 min under heating at 80 ºC the solution was stirred, RSC Advances Page 4 of 20 after that, the quantity of urea was added. The full precursor solution dried at 100ºC in a porcelain crucible with a glass-watch lid. The solution was introduced into a furnace maintained at 400ºC and heated up to 600°C; where the ignition took place in a few minutes (CA. 10 min). A white powder with an extremely porous and foam structure was obtained. Selected synthesized powders were also thermally treated at 600 or 900ºC in a furnace under argon atmosphere to improve the luminescent properties. Phase identification of the powders was determined by X-ray diffraction analysis using a Bruker diffractometer (D8, Bruker, Germany) using Cu Kα. The microstructure of the samples was evaluated using secondary electron images of field emission scanning electron microscopy (FESEM, Hitachi S-4700). Image analysis of FESEM micrographs was used to determine the grain evolution by using an Image analysis program (Leica Qwin, Leica Microsystems Ltd, Cambridge, England) considering more than 100 grains in each measurement. Optical properties of these materials by measuring emission and excitation spectra were Manuscript investigated. The photoluminescence spectra of the phosphor particles were recorded with a spectrofluorometer (Fluorolog®-3, HORIBA Jobin Yvon) at room temperature. The luminescence intensity was measured over the wavelength 425–650 nm, a Xenon arc lamp was used as excitation source (λexc= 380nm and 464nm). The decay profiles were also recorded using the same instrument after the samples were sufficiently excited for about 5 min. Accepted 3. Results and discussion 3.1. Influence of the ratio of urea on the synthesis Structural characterization Concerning the combustion synthesis, the urea content and the oxidizing agent ratio are studied. X -ray Advances diffraction patterns of the combustion powders by using the stoichiometric amount of urea, m=1 and excess, m=2 and 3, are shown in Fig. 1. The combustion reaction for m=1 produces a powder which XRD patterns show major crystalline phase as unreacted raw materials and minor presence of Sr (NO3) 2. The main RSC appearance of SrCO3 indicates the carbonation of the nitrate species owing to the reaction medium created by carbon dioxide during the combustion. The peaks of Sr(NO3)2 are related to starting Sr(NO3)2, indicating that the reaction is uncompleted in agreement with previous reported result [10-13].
Load more

Recommended publications
  • Synthesis and Characterization of Sral4o7:Eu Nanophosphors
    International Journal of NanoScience and Nanotechnology. ISSN 0974-3081 Volume 7, Number 1 (2016), pp. 57-61 © International Research Publication House http://www.irphouse.com Synthesis and Characterization of SrAl4O7:Eu Nanophosphors V.T. Jisha Research Centre, S.T. Hindu College, Nagercoil -629 002, Tamilnadu, India. Abstract Monoclinic Eu activated Strontium aluminate phosphor was successfully synthesized by a sol–gel method method at a relatively low temperature . The prepared samples were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and photoluminescence emission spectra (PL). The photoluminescence emission was obtained at 395 nm, 520 nm,790 nm corresponding to blue, green and IR region of the spectrum, respectively.The XRD analysis showed that SrAl4O7: Eu have monoclinic structure. Keywords: XRD, FTIR, SEM, sol–gel method , Photoluminescence. INTRODUCTION The scientific researches on phosphors have a long history going back to more than 100 years.The rare earths are a unique series of elements in so far as they have an inner shell of electrons which is not full. The 3d and 4d shells of the first and second transition series elements are also unfilled but they are admixed to some extent with the valence band permitting the d electrons to become involved in chemical bonding. In the rare earth elements (lanthanides),however the unfilled 4f shell is truly an inner shell and the 4f electrons play little part in chemical bonding. Optical properties of rare-earth ions in nanostructure materials have also been extensively studied,the life time emission,the quantum- efficiency and the concentration quenching are some of the crystallite size-dependent properties in these materials [1–5].
    [Show full text]
  • Application of Green Solvents for Rare Earth Element Recovery from Aluminate Phosphors
    minerals Article Application of Green Solvents for Rare Earth Element Recovery from Aluminate Phosphors Clive H. Yen * and Rui Cheong Department of Cosmetic Science, Providence University, Taichung City 43301, Taiwan; [email protected] * Correspondence: [email protected]; Tel.: +886-4-2632-8001 (ext. 15416) Abstract: Two processes applying green solvents for recovering rare earth elements (REEs) from different types of aluminate phosphors are demonstrated in this report. For magnesium aluminate- type phosphors, a pretreatment with peroxide calcination was implemented first, and then followed by a supercritical fluid extraction (SFE) process. Supercritical carbon dioxide (sc-CO2) provides an effective and green medium for extracting REEs from dry materials. With the addition of a complex agent, tri-n-butyl phosphate-nitric acid complex, highly efficient and selective extraction of REEs using supercritical carbon dioxide can be achieved. The highest extraction efficiency was 92% for europium from the europium doped barium magnesium aluminate phosphor (BAM), whereas the highest extraction selectivity was more than 99% for the REEs combined from the trichromatic phosphor. On the other hand, for strontium aluminate type phosphors, a direct acid leaching process is suggested. It was found out that acetic acid, which is considerably green, could have high recovery rate for dysprosium (>99%) and europium (~83%) from this strontium aluminate phosphor materials. Nevertheless, both green processes showed promising results and could have high potential for industrial applications. Citation: Yen, C.H.; Cheong, R. Keywords: rare earth elements; phosphors; supercritical carbon dioxide; aluminate; acid leaching Application of Green Solvents for Rare Earth Element Recovery from Aluminate Phosphors.
    [Show full text]
  • Novel Method of Phosphorescent Strontium Aluminate Coating Preparation on Aluminum
    Materials and Design 160 (2018) 794–802 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes Novel method of phosphorescent strontium aluminate coating preparation on aluminum Ivita Bite, Guna Krieke, Aleksejs Zolotarjovs, Katrina Laganovska, Virginija Liepina, Krisjanis Smits ⁎, Krisjanis Auzins, Larisa Grigorjeva, Donats Millers, Linards Skuja Institute of Solid State Physics, University of Latvia, Latvia HIGHLIGHTS GRAPHICAL ABSTRACT • A new one-step plasma electrolytic oxida- tion process of strontium aluminate coat- ing on aluminum alloy is demonstrated. • It was applied for production of an effi- cient long-afterglow phosphor SrAl2O4: Eu2+,Dy3+ on aluminium alloy Al6082. • The obtained coating exhibits optical properties similar to commercial 2+ 3+ SrAl2O4:Eu ,Dy phosphor. • The formation of strontium aluminate oc- curs during the local high-temperature plasma discharges. • This method provides an engineering so- lution for metal surface coatings having both protective and functional properties. article info abstract Article history: This study presents a novel approach to produce phosphorescent coatings on metal surfaces. Received 12 July 2018 Strontium aluminates are the most popular modern phosphorescent materials exhibiting long afterglow at room Received in revised form 12 October 2018 temperature and a broad spectral distribution of luminescence in the visible range. However, despite a large Accepted 13 October 2018 amount of research done, methods for synthesis of such materials remain relatively energy inefficient and Available online 15 October 2018 environmentally unfriendly. 2+ 3+ Keywords: A long-afterglow luminescent coating containing SrAl2O4:Eu ,Dy is prepared by the plasma electrolytic Phosphorescent coating oxidation on the surface of commercial aluminum alloy Al6082.
    [Show full text]
  • EU2+, DY3+, ER3+/ ND3+ NANOPHOSPHORS by NAIYIN YU
    SUNLIGHT-EXCITED INFRARED LONG PERSISTENCE OF 2+ 3+ 3+ 3+ SRAL2O4: EU , DY , ER / ND NANOPHOSPHORS by NAIYIN YU (Under the Direction of Zhengwei Pan) ABSTRACT Strontium aluminate co-doped with divalent europium, trivalent dysprosium ions 2+ 3+ (SrAl2O4: Eu , Dy ) shows a green demonstrated long persistence lasting for up to 15 hours under sunlight excitation. The research presented in this thesis focus on the Er3+/ Nd3+ activated 2+ infrared (IR) long persistence due to the persistent energy transfer process in SrAl2O4: Eu , Dy3+, Er3+/ Nd3+ nanophosphor system. The XRD, SEM, EDX and optical spectra analysis method are employed to characterize the phosphors synthesized by combustion route. The 2+ 3+ 3+ efficient energy transfer process from sensitizer Eu to the activator Er / Nd in SrAl2O4 host system is investigated. Meanwhile, the long persistence luminescence in IR region is obtained. To our knowledge, there is no related material system regarding sunlight-excited infrared long persistence nanophosphor reported. 2+ 3+ 3+ 3+ INDEX WORDS: SrAl2O4: Eu , Dy , Er / Nd , Infrared (IR) long persistence, Persistent energy transfer SUNLIGHT-EXCITED INFRARED LONG PERSISTENCE OF 2+ 3+ 3+ 3+ SRAL2O4: EU , DY , ER / ND NANOPHOSPHORS by NAIYIN YU B.S., Shanghai Jiao Tong University, China, 2006 A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE ATHENS, GEORGIA 2008 © 2008 NAIYIN YU All Rights Reserved SUNLIGHT-EXCITED INFRARED LONG PERSISTENCE OF 2+ 3+ 3+ 3+ SRAL2O4: EU , DY , ER / ND NANOPHOSPHORS by NAIYIN YU Major Professor: Zhengwei Pan Committee: Loris Magnani Heinz-Bernd Schüttler Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia August 2008 iv ACKNOWLEDGEMENTS Thanks to Dr.
    [Show full text]
  • Preparation and Properties of Long Persistent Sr4al14o25 Phosphors Activated by Rare Earth Metal Ions
    Preparation and Properties of Long Persistent Sr4Al14O25 Phosphors Activated by Rare Earth Metal Ions March 2010 Department of Energy and Materials Science Graduate School of Science and Engineering Saga University HOM NATH LUITEL Preparation and Properties of Long Persistent Sr4Al14O25 Phosphors Activated by Rare Earth Metal Ions By Hom Nath LUITEL Supervisor: Professor Dr Takanori Watari A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree of Philosophy in Applied Chemistry Doctor of Philosophy Department of Energy and Materials Science Graduate School of Science and Engineering Saga University March 2010 ABSTRACT Preparation and Properties of Long Persistent Sr4Al14O25 Phosphors Activated by Rare Earth Metal Ions Chairperson of the Supervisory Committee: Professor Takanori WATARI Department of Energy and Materials Science, Saga University This work comprises of several aspects of phosphor materials, especially, strontium aluminate phosphor activated with rare metal ions. The 1st chapter gives a brief and general background of phosphor materials, its synthesis methods and underlined phosphorescence mechanisms. nd 2+ 3+ In 2 chapter, long persistent Sr4Al14O25:Eu /Dy blue-green phosphor was prepared by solid state reaction method. The effect of synthesis parameters like calcinations temperature and time, calcinations environment and effect of additives like addition of boron and rare earth ions (Eu2+, Dy3+) were studied in detail. When the phosphor was prepared adding 4 mol% H3BO3, it showed dense microstructure composed of pure Sr4Al14O25 phase showing higher emission intensity. But in the samples containing less than 3.5 mol% H3BO3, mixed phases consisting of Al2O3, SrAl12O19 and SrAl2O4 were observed, while if higher H3BO3 content (8 mol%) was used, SrAl2B2O7 phases predominated.
    [Show full text]
  • Luminescence Studies of Rare Earth (Europium) Doped Nano-Crystalline Strontium Aluminate Materials 2+ (Sra2o4:Eu )
    International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009 Special Issue-1, June-2015 LUMINESCENCE STUDIES OF RARE EARTH (EUROPIUM) DOPED NANO-CRYSTALLINE STRONTIUM ALUMINATE MATERIALS 2+ (SRA2O4:EU ) BELEKAR R. M.*, SAWADH P. S.#, MAHADULE R. K.$, THENG P. A.$ *Arvindbabu Deshmukh Mahavidyalaya, Bharsingi, Distt.-Nagpur, Maharashtra State, India-441305 #Bapurao Deshmukh college of Engineering, Sevagram, Distt.- Wardha, Maharashtra State, India-442 102 $Tulsiramji Gaikwad - Patil College of Engineering & Technology, Nagpur, Maharashtra State, India-441108 *Corresponding Author e-mail: [email protected] Abstract: In the present work we have prepared ultraviolet to near infrared wavelength, excellent nano-crystalline rare earth doped strontium aluminate mechanical properties, and good chemical stability. as Sr1-xEuxAl2O4, (with x = 0.01, 0.02 & 0.03) via sol Similarly, among the variety of RE ions commonly gel auto combustion technique. The homogeneity, used to dope different kinds of materials, europium structure as well as UV-excitation and persistent ions (Eu3+) have attracted significant attention luminescence of the materials was investigated by X- because they have tremendous potential for ray powder diffraction, SEM microscopy as well as applications as phosphors, electroluminescent by steady state luminescence spectroscopy and devices, optical amplifiers or lasers, and high density persistent luminescence decay curves, respectively. optical storage. The morphology of the materials at high temperatures 2. Materials: indicated important aggregation due to sintering. The The Eu2+ doped strontium aluminate were prepared luminescence decay of the quite narrow Eu2+ band at by solution combustion synthesis (SCS) using urea as ca. 525 nm shows the presence of persistent fuel with different concentration of dopent (0.01 %, luminescence after UV irradiation.
    [Show full text]
  • The Influence of Boric Acid on Improved Persistent Luminescence
    Journal of Luminescence 167 (2015) 126–131 Contents lists available at ScienceDirect Journal of Luminescence journal homepage: www.elsevier.com/locate/jlumin The influence of boric acid on improved persistent luminescence 2 þ and thermal oxidation resistance of SrAl2O4:Eu Songhak Yoon a,n, Jakob Bierwagen b, Matthias Trottmann a, Bernhard Walfort c, Nando Gartmann c, Anke Weidenkaff d, Hans Hagemann b, Simone Pokrant a a Laboratory Materials for Energy Conversion, Empa-Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, CH-8600 Dübendorf, Switzerland b Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, CH-1211 Geneva 4, Switzerland c LumiNova AG, Switzerland, Speicherstrasse 60a, CH-9053 Teufen, Switzerland d Institute for Materials Science, University of Stuttgart, Heisenbergstrasse 3, DE-70569 Stuttgart, Germany article info abstract 2þ Article history: Persistent luminescence of SrAl2O4:Eu has attracted considerable attention due to their high initial Received 27 March 2015 brightness, long-lasting time and excellent thermal stability. Here the influence of boric acid on the Received in revised form 2þ persistent luminescence and thermal oxidation resistance of SrAl2O4:Eu was investigated in detail. 26 May 2015 Crystal structural analysis and scanning electron microscopy revealed that with the addition of boron, Accepted 15 June 2015 the unit cell volume decreased and the morphology of the particles became more irregular with sharp Available online 23 June 2015 edges. Thermogravimetric analysis showed better thermal oxidation resistance accompanied by a change Keywords: in oxygen vacancy concentration when boron acid is used. Photoluminescence spectra and afterglow Persistent luminescence 2þ decay curves confirm an improved afterglow performance for boron-added SrAl2O4:Eu .
    [Show full text]
  • Chemistry of Core Glow: 2+ Crystalline Strontium Aluminate Sral2o4:Eu
    Chemistry of Core Glow: 2+ Crystalline Strontium Aluminate SrAl2O4:Eu Glow in the dark materials are phosphorescent and always Reactivity Data: contain a ‘phosphor’. There is a quick light absorption and slow Stability: stable light emission which results in the glow in the dark phenomena. Hazardous Polymerization: will not occur Conditions to Avoid: contact with acids solid powder, nonflammable, pale yellow, Strontium Aluminate: Incompatibility: contact with acids monoclinic crystalline, non-radioactive, chemically and Hazardous Decomposition Products: will not occur[4] biologically inert[2][4]. Strontium aluminate is 10x brighter and has a 10x longer glow than its dimmer predecessor, copper-activated Colours: Three colours are available. The colour emission zinc sulfide. changes with the number of oxygen atoms, which directly affects the internal crystal structure of the final material. 2+ Chemical Formula: SrAl2O4:Eu Blue: 400nm: SrAl2O19 Advanced glow technologies use strontium aluminate doped with Aqua: 480nm: SrAl2O7 europium to activate the phosphorescent properties of strontium Green: 520nm: SrAl2O4 aluminate. The europium interacts via covalent interactions with the oxygen atoms and crystal field splitting of the 5d orbital[2]. Q. What is doping? A. Purposely mixing in an impurity to activate desired properties. Q. What is europium? A. Europium is a reactive rare earth metal which readily oxidizes in air and water. It is commonly used in fluorescent lights and CRT TV displays. Q. Is strontium aluminate doped with europium toxic? A. Strontium aluminate doped with europium is non toxic. Strontium aluminate phosphors are harmless as defined by the Laws of Chemical Substances. Our product specifically was deigned harmless under the OSHA (Occupational Safety and Health Administration) Hazard Communication Standard 29 CFR Fig.
    [Show full text]
  • Long Afterglow Phosphors N EXECUTIVE SUMMARY
    SCIENCE-53 Long Afterglow Phosphors n EXECUTIVE SUMMARY Phosphorescence (afterglow) refers to the light emission at room temperature from a material that persists after removal of the excitation source. A long glow green phosphorescent material based on strontium aluminates has been developed. This indigenous phosphor once irradiated with visible light exhibits intense emission for hours in absence of any exciting light. This material can act as a path finder in industrial environment during black out conditions. It can also be used to find out different components in dark if these are painted with this material. The enhanced light output of this phosphor is at par with the available international commercial phosphors. n OUTLINE Phosphors based on oxide matrices are attractive host materials for the development of advanced phosphors due to their ease of synthesis and stability. Rare earth doped aluminates serve as an important class of phosphors for fluorescent lamp and phosphorescence applications. We have developed a long afterglow phosphors 2+ 3+ Sr41425 Al O :Eu ,Dy (Fig. 1) and studied its photoluminescence and phosphorescence properties. The stoichiometry of the reacting metal ions and method of preparation can significantly affect the luminescence properties of a phosphor. A study on the non- 2+ 3+ stoichiometry behavior of (Sr41425 Al O :Eu , Dy ) has been carried out to understand the mechanism of phosphorescence phenomenon in aluminates and develop a Long After Glow Phosphor. The stoichiometry was varied 2+ 3+ Fig. 1 : Afterglow emission from Sr Al O :Eu ,Dy at 490 nm by taking different Sr/Al molar ratio. Photoluminescence 41425 intensity of both the strontium deficit and rich phosphors was enhanced whereas no definite correlation was observed between the afterglow intensity and non- stoichiometry.
    [Show full text]
  • Crystal Structure, Photoluminescence and Cathodoluminescence of Sr1−Xcaxal2o4 Doped with Eu2+
    Research Article Vol. 9, No. 5 / 1 May 2019 / Optical Materials Express 2175 Crystal structure, photoluminescence and cathodoluminescence of Sr1−xCaxAl2O4 doped with Eu2+ LIPING YU,2 DANIELDEN ENGELSEN,1 JÜRGEN GOROBEZ,3 GEORGE R.FERN,1 TERRY G.IRELAND,1,* CHRIS FRAMPTON,1 AND JACK SILVER1 1Centre for Phosphor and Display Materials, Wolfson Centre for Materials Processing, Brunel University London, Uxbridge, Middlesex, UB8 3PH, UK 2On leave from the College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha, 410081, China 3On leave from Department of Chemical Engineering, University of Applied Sciences Münster, Stegerwaldstrasse 39, D-48565, Steinfurt, Germany *[email protected] Abstract: The crystal structure, photoluminescence and some cathodoluminescent spectra of 2+ Sr0.99−xCaxEu0.01Al2O4 (Eu ) are described. Five different phases have been found: three different monoclinic phases, one hexagonal and one cubic phase. Based on the cathodolumines- 2+ 2+ cence of SrAl2O4:Eu at low temperature and photoluminescence of Sr1−xCaxAl2O4:Eu at 0 ≤ x ≤ 0.1, we consider an alternative explanation for the origin of the 440 nm peak in the low 2+ temperature spectrum of SrAl2O4:Eu , namely that it can be attributed to the emission from 2+ Eu ions situated on the alkaline earth sites of the monoclinic P21/n structure that generate the 440 nm emission of CaAl2O4. However, this alternative hypothesis has been eliminated by XRD analyses of SrAl2O4 at low temperature. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
    [Show full text]
  • Novel Method of Phosphorescent Strontium Aluminate Coating Preparation on Aluminum
    Materials and Design 160 (2018) 794–802 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes Novel method of phosphorescent strontium aluminate coating preparation on aluminum Ivita Bite, Guna Krieke, Aleksejs Zolotarjovs, Katrina Laganovska, Virginija Liepina, Krisjanis Smits ⁎, Krisjanis Auzins, Larisa Grigorjeva, Donats Millers, Linards Skuja Institute of Solid State Physics, University of Latvia, Latvia HIGHLIGHTS GRAPHICAL ABSTRACT • A new one-step plasma electrolytic oxi- dation process of strontium aluminate coating on aluminum alloy is demon- strated. • It was applied for production of an effi- cient long-afterglow phosphor SrAl2O4: Eu2+,Dy3+ on aluminium alloy Al6082. • The obtained coating exhibits optical properties similar to commercial 2+ 3+ SrAl2O4:Eu ,Dy phosphor. • The formation of strontium aluminate oc- curs during the local high-temperature plasma discharges. • This method provides an engineering so- lution for metal surface coatings having both protective and functional properties. article info abstract Article history: This study presents a novel approach to produce phosphorescent coatings on metal surfaces. Received 12 July 2018 Strontium aluminates are the most popular modern phosphorescent materials exhibiting long afterglow at room Received in revised form 12 October 2018 temperature and a broad spectral distribution of luminescence in the visible range. However, despite a large Accepted 13 October 2018 amount of research done, methods for synthesis of such materials remain relatively energy inefficient and Available online 15 October 2018 environmentally unfriendly. A long-afterglow luminescent coating containing SrAl O :Eu2+,Dy3+ is prepared by the plasma electrolytic Keywords: 2 4 Phosphorescent coating oxidation on the surface of commercial aluminum alloy Al6082.
    [Show full text]
  • Mechanism for Long Persistent Phosphorescence in Sr2mgsi2o7:Eu
    2+ Mechanism for long persistent phosphorescence in Sr2MgSi2O7:Eu by Mark E. Hannah (Under the direction of Uwe Happek) Abstract In this thesis I will discuss the historical research on the phosphor material 2+ 2+ SrAl2O4:Eu , as well as Sr2MgSi2O7:Eu . Both of these phosphors are possible replacements for the ¯rst generation green phosphor materials. I will also discuss my own research on these phosphors, as well as propose a new mechanism for the long persistent phosphorescence seen in these materials. Index words: phosphor, luminescence, Strontium, aluminate, magnesium, silicate, rare earth 2+ Mechanism for long persistent phosphorescence in Sr2MgSi2O7:Eu by Mark E. Hannah BS, Oglethorpe University, 1996 MA, The University of Georgia, 2002 A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Ful¯llment of the Requirements for the Degree Masters of Science Athens, Georgia 2008 °c 2008 Mark E. Hannah All Rights Reserved 2+ Mechanism for long persistent phosphorescence in Sr2MgSi2O7:Eu by Mark E. Hannah Approved: Major Professor: Uwe Happek Committee: Bernd Schuttler William Dennis Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia December 2008 Table of Contents Page Chapter 1 Phosphor Materials . 1 1.1 Luminescence and Phosphor Materials . 1 1.2 Applications of Luminescent Materials . 4 2 Persistent Luminescence . 7 2.1 Early Phosphors . 7 3 Long Persistence Mechanism Debate . 8 3+ 4 Sr2MgSi2O7:Eu ........................... 22 5 New Work . 25 5.1 Formulation . 25 5.2 Experiments . 25 6 Results . 34 7 Conclusion . 45 Bibliography . 46 iv Chapter 1 Phosphor Materials 1.1 Luminescence and Phosphor Materials As an observed phenomena luminescence has been around since ancient times.
    [Show full text]