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1
Zhang, Shuo. "Phosphors and photonic crystals." Thesis, University of Greenwich, 2008. http://gala.gre.ac.uk/8404/.
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Y2WO6: RE, Y2O2S: RE, Gd2O2S: RE phosphors have been prepared using the urea homogeneous precipitation method and firing. Stokes luminescence properties of Y2WO6: RE excited with a FRED (frequency doubled argon ion) UV laser (257 nm) have been studied. The emissions have been assigned to their corresponding energy levels. Differences in the emission spectra of Y2WO6: RE, Y2O2S: RE, Gd2O2S: RE and Y2O3: RE have been attributed to the different site symmetries of the rare earth ions and to the different phonon energies of the lattices. Fine nanostructures present within butterfly wing scales have been faithfully replicated using a precursor Y2O3: Eu phosphor solution. Monodisperse polystyrene spheres and SiO2 spheres were synthesised and they were used to synthesise well ordered bare opal templates. Photonic phosphor crystals of Y2O3: Eu, Tb, Gd and Y2O3: Tm were synthesised using these templates to study the photonic band gap properties. Nano-sized Y2O3: Eu phosphors have been successfully incorporated into mono-dispersed silica spheres which have been assembled into photonic crystals. It has been observed that when light-emitting phosphors (e.g. Y2O3: Eu) and dyes (e.g. acid red dye) are incorporated into the opal structures, their emission spectra are modified when the stopbands of the opals overlap the emission bands of the light-emitting materials.
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Ranson, Robert Marcus. "Investigation into thermographic phosphors." Thesis, Nottingham Trent University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297737.
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Yan, Xiao. "Phosphors for lighting applications." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/6954.
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Trivalent rare earth cations (RE3+) activated nanometre-sized Y2O2S and Gd2O2S phosphors were prepared by converting hydroxycarbonate precursor powders during a firing process. The precursors were prepared using the urea homoprecipitation method. The choice of host crystal and dopant were optimised to meet the specific requirements for practical applications in the field of lighting, X-ray detection, and displays. Parameters that affect the luminescent properties of the resulting phosphors, such as doping concentration, excitation mechanism, firing temperature, and host lattice were investigated. Tb3+ and Er3+ co-doped Y2O2S and Gd2O2S were studied for their upconversion properties under 632.8 nm red laser excitation. The intensities of UC emission were affected by both doping concentration and host lattices. Tb3+ and Er3+ co-doped Y2O2S was found to show strong downconversion from Tb3+ and upconversion from Er3+. The presence of the Er3+ cations directly affects the Tb3+ down-converting properties by acting as centres for energy transfer. The possible energy transfer between Gd3+ and Er3+ should be responsible for the different trend of Er3+ upconversion intensity in Y2O2S and Gd2O2S. It has been established that the Tb3+ and Er3+ co-doped system is superior than the Yb3+ and Er3+ co-doped one. In the latter system the presence of Yb3+ reduces the efficiency of both upconversion and downconversion emission under red laser excitation. These phosphors show potential applications in the security and anti-fraud field. The novel ZnS:Mn QDs were prepared and successfully incorporated into GaN based photonic crystal (PC) holes to efficiently produce white light. The crystal structure and luminescent properties of the ZnS:Mn QDs were investigated as well as the factors affecting the filling rate. Zn1-xCdxS:Mn QDs were also investigated. The addition of Cd cations leads to a red shift in the PL excitation spectra of the Zn1-xCdxS:Mn QDs. The crystal structures and surface properties were also affected by the presence of Cd. Monodisperse PbS QDs with particle size of ~5 nm has been obtained using a similar aqueous reaction method.
4
Aubauer, Christoph. "Halogen-, Azid- und Koordinationsverbindungen des Phosphors." Diss., [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963037900.
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Furman, Joshua D. "Novel phosphors for solid state lighting." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/228686.
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Solid state white light emitting diode lighting devices outperform conventional light sources in terms of lifetime, durability, and lumens per watt. However, the capital contribution is still to high to encourage widespread adoption. Furthermore, the colour from today's devices is unsuitable for general room illumination and thus new phosphor materials are needed. This dissertation will examine the synthesis of inorganic nanoparticles and the possibility of using hybrid inorganic-organic frameworks in the search for new lighting phosphors. Nanoparticles of the oxide compound yttrium aluminium garnet were synthesized using an emulsion technique, though it was found that the high temperature processing needed for good optical properties was not compatible with maintaining nanosized particles. In terms of hybrid framework phosphors, several aspects of this new area have been explored. The mechanical and optical properties of a dense cerium oxalate formate hybrid framework compound have been investigated. Its strength was found to be nearly as great as some classical ceramic compounds, and clearly robust enough for device applications. While the photoluminescence of the cerium oxalate formate was not suitable for solid state lighting, the impressive mechanical properties evaluated are expected to be valid for a wide range of dense inorganic-organic frameworks. A novel approach to solid state lighting phosphors was introduced by using ligand-based photoluminescence in hybrid frameworks. Novel frameworks were prepared using 9,10-anthraquinone-2,3-dicarboxylic acid in combination with calcium, manganese, nickel, and zinc. These compounds show excellent photoluminescent emission for use in solid state lighting applications, although the luminescence is quenched at room temperature due to dynamic effects. The excitation, while reaching the blue part of the spectrum, falls just short of what is needed for use today's devices. To address these issues, a second class of novel framework compounds was prepared using 9-fluorenone-2,7-dicarboxylic acid in combination with calcium, strontium, barium, cadmium, and manganese. They are more rigid structures and show good luminescence at room temperature with a photoluminescent excitation spectrum extending further into the blue than the anthraquinones. Additionally, quantum yield in the calcium fluorenone is nearly double that of its parent ligand, suggesting that there is an enhancement in luminescent properties as a result its inclusion in a framework structure. An explanation for the differences in efficiency between seemingly similar compounds are drawn from their compositions, crystal structures, photoluminescence, and specific heat properties. Finally, some structural and chemical targets for future hybrid phosphor development are identified based on the relationships identified in this work.
6
Park, Wounjhang. "Optical properties of thin film phosphors." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/30078.
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Stoffers, Christian. "Saturation kinetics of low voltage phosphors." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/31047.
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Ng, Ka Man. "Near-ultra-violet (NUV) excited phosphors." HKBU Institutional Repository, 2008. http://repository.hkbu.edu.hk/etd_ra/915.
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Cheng, Pui Yan. "Vacuum ultra-violet (VUV) excited phosphors." HKBU Institutional Repository, 2006. http://repository.hkbu.edu.hk/etd_ra/701.
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Latini, Alessandro. "Inorganic Nanostructured Materials for Technological Applications." Doctoral thesis, La Sapienza, 2006. http://hdl.handle.net/11573/917353.
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Manigault, Patrick Alexander. "Second order luminescent saturation effects in phosphors." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/30700.
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Yap, Sook Voon. "Phosphors for biomedical and environmental sensing technology." Thesis, Nottingham Trent University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510264.
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Temperature measurement in an electromagnetically hostile environment, such as a magnetic resonance imaging (MRI) scanner, is challenging. The monitoring of a patient's temperature within an MRI is necessary to ensure the patient is in a comfortable condition due to the following problem. Unfortunately, the radio frequency (RF) radiation in the imaging cavity of an MRI will induce heat into both the body tissue of a patient as well as into metallic elements of any sensors. This thesis presents a feasibility study on the production of an optical phosphor-based sensor for temperature monitoring within such a hostile environment. The concept of a desired optical sensor is based on the thermal dependence of phosphor luminescence. A pulsed ultraviolet light source is used to excite phosphors coated on a thin membrane which is in contact with the patient's skin. The skin temperature (over 27-37 ·C) can then be determined by calculating the exponential decay of luminescence intensity with time after the excitation pulse has ceased. In this research, two thermographic phosphors have been investigated, namely europium doped lanthanum oxysulphide (La202S: Eu) and terbium doped lanthanum oxysulphide (La20 2S: Tb). A wide range of dopant concentrations, 0.005-15 mol% for La20 2S: Eu and 0.005-50 for mol% La202S: Tb, have been characterised in terms of photoluminescent emission, decay time and crystallinity in determining their temperature dependent characteristics. Both phosphors have shown a dependency to dopant concentration through variance of peak intensity and decay time measurements over a low temperature range of 5 to 60°C. Although maximum brightness of the temperature dependent lines is achieved at dopant concentrations of 1 and 10 mol% for La202S: Eu and La2~S: Tb respectively, results have shown that optimum temperature dependency is at a lower mol% of 0.1 for La202S: Eu with a high quenching rate of 24.03 moe-I. Therefore, 0.1 mol% L1l202S: Eu appears to be an ideal candidate for use within an optical sensor. A key aspect of this research is that in comparison to conventional phosphor temperature dependent characteristic, it has been shown for the first time that La20 2S: Tb has an increase in decay time with respect to temperature for concentrations above 2 mol%. A hypothesis of this discovery based on the differences in energy transfer pathways is described. X-ray diffraction (XRD) analysis has demonstrated a linear relationship between the c-axis lattice parameter of a unit cell of the phosphors with dopant concentration. As dopancy increases, the (100) and (002) reflections merge and there is a reduction in the c-axis parameter as well as the crystallite size. In addition, a positive thermal expansion behaviour is observed for a and c parameters as well as the volume of the unit cell over the temperature range of interest
13
Jones, Thomas C. "Luminescence properties of strontium sulfide thin-film phosphors." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30351.
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Kalaji, Ali. "Novel cerium-doped phosphors for solid-state lighting." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607693.
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Li, Janice Joyce. "Development platform for immunoassays with up-converting phosphors /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Shea, Lauren Elizabeth. "ZnGa₂O₄ and ZnGa₂O₄:Mn²⁺ for potential use in vacuum fluorescent displays /." This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-01102009-063207/.
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Chen, Tai-Chang. "An investigation of thermal effects on thermoluminescent processes in LiF:Mg,Cu,P phosphors /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10567.
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Schweizer, Stefan. "Physics and current understanding of X-ray storage phosphors." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=962295574.
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Green, A. G. J. "Luminescence and trapping states in calcium sulphide based phosphors." Thesis, Coventry University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234157.
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Rose, John Andrew. "Studies of luminescent materials including novel preparation of phosphors." Thesis, University of Greenwich, 2004. http://gala.gre.ac.uk/6284/.
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New, clean, methods of zinc sulphide synthesis were established in order to produce small regular particles with comparable luminescence to that of commercial standards in current use. These new methods are optimised for activator and co-activator concentrations, firing conditions and other factors affecting the phosphor synthesis process. Microgels have also been used for the first time in the zinc sulphide preparation process. The resultant small, regular spherical sized particles have similar luminescent properties to those of the commercial standards available. The potential of tin oxide as a host lattice for the synthesis of phosphors has been studied. It is concluded that tin oxide cannot compete against established host lattices. A tin oxide:europium phosphor was prepared which shows luminescence in the red region of the spectrum but the intensity of this emission is very weak when compared against a commercial red standard phosphor. However the novel preparation techniques utilising microwave technology could prove useful for the synthesis of nano sized tin oxide materials. For any group of chemical materials it is important to examine potential novel uses. The aforementioned has been undertaken by incorporating a phosphor material into a ceramic frit. Different phosphors retained their luminescent properties even after being mixed into ceramic frits in much the same way dye is incorporated and fired. Numerous niche products could result from such a process. Luminescence in the animal kingdom has also been examined; this work is reported in the first part of the appendix. Scorpion and horseshoe crab emission spectra have been obtained, and in the case of the scorpion samples it is possible to examine emission spectra at different wavelengths.
21
Al-Waisawy, Sara S. "Investigation of Color Phosphors for Laser-Driven White Lighting." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1417065501.
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Zhang, Jian. "Studies on high luminance Eu[2+]-doped thiogallate phosphors." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/145370.
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Arterton, Bruce William. "Preparation related luminescent properties in II-VI sulphides." Thesis, Coventry University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386517.
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Sivakumar, Praveen. "Analysis of electron transport and luminance in SrS based blue emitting A.C. thin film electroluminescent devices." Lexington, Ky. : [University of Kentucky Libraries], 2003. http://lib.uky.edu/ETD/ukyelen2003t00114/PKSThes.pdf.
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Thesis (M.S.)--University of Kentucky, 2003.Title from document title page (viewed Sept. 10, 2004). Document formatted into pages; contains xii, 140 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 139).
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Ghazli, Mohd Fathullah bin. "An investigation into red emitting phosphors for display and lightings." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/12855.
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An Investigation into Red Emitting Phosphors for Display and Lightings Two very different classes of red phosphors were evaluated in this thesis; sulphide based phosphors (CaS:Eu2+) and phosphors based on the formulae:- LiEu1- xMx(MoO4)2-y(WO4)y, [M=Al3+, Y3+ and Gd3+]. CaS:Eu2+ was coated with Al2O3 using atomic layer deposition technique and placed into a humidity chamber at high temperature and high humidity for a period of time. The emission spectra were measured and evaluated against uncoated CaS:Eu2+. The results from the humidity tests revealed that Al2O3 coated CaS:Eu2+ increased the life span of the phosphor and therefore can be the potential use for the purpose of application at moderate humidity and temperature. For the phosphors based on LiEu1-xMx(MoO4)2-y(WO4), all the findings reported herein showed that, depending upon the types of cations introduced to the host lattices, incorporation of M at some point offered very much the same or better luminous efficacy when compared to the parent compound with 100 mol% of Eu3+. This work also attempted to examine the correlative relationship between the crystal structures and the luminous efficacies although some attempts were unsuccessful. The findings discovered within this research are beneficial for solid state lighting industries where the cost of using rare earth metals has become significant and recycling is difficult.
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Pedruelo, Maria del Puy Rebollo. "Chemical Control of the Photoluminescent Properties of Up-Converting Phosphors." Thesis, Open University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486505.
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Up-conversion luminescence of Er3+ based phosphors was studied in the following host lattices: Y203, Gd20 3, Gd2_xYx03, and YV04, with a view to developing an understanding of how emission can be tailored by manipulating the local chemical environment of the activator ion. Laser induced luminescence measurements of Y203:Er phosphors showed evidence of Stokes and Anti-Stokes emission bands arising from excited levels under 632.8 nm radiation. Emission from 4F7I2~ 4115/2 transitions were found to be \yeaker in Gdz03 phosphors and were not dete~ted in YV04 hosts. Relative intensity of Stokes I Anti-Stokes radiation were studied as a function of the host lattice, and variations found as a consequence of crystal field changes in the activator environment. This work was extended to an investigation of the effect of co-dopants. Low levels of Yb3+ used as sensitizer, enhanced luminescence from 4F7I2~ 4115/2 and 4F912~ . 4~1512 transitions, and a novel relaxation mechanism involving energy transfer from excited states is proposed to account for the variation observed in the intensity of the emission bands. Eu3+ used as co-dopant produced energy loss due to resonant energy transfer. This phenomenon was demonstrated by undertaking thermal studies on YV04:Er,Eu co-doped phosphors. Enhancement of 4Hll/2 transitions from Er3+ ions in S6 symmetry sites was observed together with 4F7I2~ 4115/2 transition activation with increasing Eu3+ concentration. With a view to producing phosphor powders suitable for device application, wet chemical routes were investigated in order to prepare the materials studied in this work. The synthetic approaches studied were urea co-precipitation and combustion synthesis, the .. reaction conditions .were carefully manipulated in order to optimise the composition and morphology of the product. Spherical uniform particles in the 300 - 600 nm range were routinely prepared.
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Stone, Roni. "An investigation into novel red emitting phosphors and their applications." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/6296.
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New red emitting phosphors, based on the double tungstate/molybdates, were discovered. Some were able to retain their luminous efficacy after substituting Y3+ for Eu3+, reducing the cost of the phosphor. This substitution was attempted for existing commercial red emitting phosphors and proved unsuccessful. Another set of phosphors based on these lattices were discovered and the emitted luminous efficacy was 140% greater than other reported Eu3+ phosphors. The best of these was Na2WO4MoO4Eu0.44Al1.34Sm0.011. The integration of phosphors to the lighting application was also studied, including improvements in light extraction for existing phosphors. ACEL panels are currently applied to many applications and were briefly examined. The more recent OLED technology was investigated and comparisons can be drawn with the ACEL panels. LEDs were also a focus of the work with a new method developed for remote application of phosphors to LEDs, based on a dome shaped encapsulant, and this was adopted commercially by a high brightness LED manufacturer. The studies on the phosphors reported herein were aimed at integrating these into commercial applications. Although this was not achieved as brightness and particles size were problematic, if it is demonstrated that further development of the synthetic methods produce phosphors with suitable attributes, this may lead to the integration in applications.
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Ou, Shi-han, and 歐錫翰. "The synthesis and characteristics of Er-doped SrBaNb2O6 phosphors andEr-doped MgBaNb2O6 phosphors." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/03269885833277637543.
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碩士國立臺南大學
自然科學教育學系碩士班
94
After being replaced by various positive ions, the property of SBN is different due to the changes in temperature and in ratio of mixture. SBN is widely used in electric dovices. Nevertheless, the researches about SBN on luminescence properties are also studied recently. In this study, we use solid mothod to prepare SrxBa1-xNb2O6 :Er and MgxBa1-xNb2O6 :Er. The powders were characterized by X-ray diffraction (XRD), exphotoluminescence excitation (PLE), photoluminescence (PL), and Raman spectrum. The experiments show that the maximum emission intensity is obtained by adding 4% Er ions in SBN and 5% Er ions in MBN. In addition, the emission intensity enlarges when the growth temperature rises. The most preferred emission intensity is gained when the growth temperature is 1200oC. While changing the ratio of lattice, SBN 60 and MBN50 possess the most preferred emission intensity. Compared with SBN, MBN exhibits a blue shift on PLE and red shift on PL.From the experiments, we have found that luminescence emission changes as the structure of lattice varies.
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Chen, Jia-Xing, and 陳家興. "Preparation and improvement in luminescence property of ZnO-based phosphors by doping process of phosphors." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/88906315012881044669.
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碩士國立高雄應用科技大學
電子工程系
97
In this study, the ZnO-based phosphor was synthesized by solid-state reaction method. Potassium (K), tungsten (W), lithium (Li) and gallium (Ga) compound were used as activators and fluxes. By understanding the different sintering temperature and time of phosphors on the impact properties; different frequency and time of abrasive powder particles on the surface of fluorescent patterns and structural characteristics of the luminescence; the experimental results from the synthesis parameters, we can see indeed phosphors will affect the wavelength and intensity of the luminescence. Finally, under the best conditions for the production of phosphors into electroluminescence to stimulate the production of optical components, to assess the power of fluorescent powder laser brightness, and color coordinates of the location. In addition, the fluorescent powder-ray laser measurement of the excitation source wavelength fixed at 325 nm, always visible light radiation dominated region.
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Kuo, Hsuan-Wei, and 郭炫偉. "The Spectrum Analysis and Prediction of Phosphor-converted White LED with Green and Red Phosphors." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/76794747574256952040.
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碩士明新科技大學
光電系統工程系碩士班
103
Generally, the phosphor-converting white Light-Emitting-Diode (LED) packages are typically fabricated by blue chip coated with green and red phosphors. However, for the phosphor-converting white LED with green and red phosphors, the re-absorption between green and red phosphors would introduce intensity deviations of the green and red emissions. The package engineers will pay a lot of effort and take excessive time to achieve the correct chromaticity of the white LEDs. In this study, we provide a method to predict the spectrum of the white LEDs through experimental analysis. With the spectrum model, the deviations of the CIE 1931 x and y between the prediction and real sample is less than 0.002; the deviation of the CCT between the prediction and real sample is less than 20K; the deviation of the CRI between the prediction and real sample is less than 3. Finally, we provide a good method to predict the spectrum of the phosphor-converting white LED with green and red phosphors with high accuracy.
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Kai-Hung, Hsu, and 徐開鴻. "Preparation and Characterization of ZnGa2O4 Phosphors." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/75050034851197274566.
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博士大同工學院
材料工程研究所
86
In this study, the preparation method of ZnGa2O4 phosphor, the calcination conditions and the effect of doping 3d transition metal ions on phosphors character were investigated.Using solid-reaction method, the effect on phosphors character on the steps of mechanical mixing and particle surface coated mixing, the conditions of calcination in air and in vacuum were compared. In doping treatment, the 3d transition metal ions, such as Mn2+、Co2+、Cr3+、Ni2+、Fe3+ etc. were doped to examining the effect of emission characteristics. The synthetic ZnGa2O4 phosphor emits a broad-band spectrum range between 370nm and 700nm, peaking at 470nm. The optimal composition of phosphors is about ZnO/Ga2O3=0.9/1(mole ratio), there it shows a stronger intensity of spectrum. The composition of phosphors with excessive ZnO will introduce additional excitation peak at 320nm and severely decrease the intensity of spectrum. The mechanical mixed powder needs to calcined at a temperature above 1℃ with longer calcination time for the synthesis of phosphors. With particle surface coating mixing method, an excellent mixture is obtained. It requires a calcination temperature only at 105℃ and as short as five hours to synthesize phosphors with good repeatability. The control of furnace atmosphere is projected to the Mn2+-doped phosphor that is greatly affected by calcination process. When calcined at air atmosphere, it exhibits two emission bands with main peak at 506nm(Mn2+ emission center) and weak peak at 666nm(Mn4+ emission center). However, when calcined at vacuum atmosphere, the emission spectrum shown only 506nm peak, and its intensity increase drastically. The 3d-series transition metal ions such as Mn2+、Co2+、Cr3+ etc. incorporated into phosphors will act as emission center. Mn2+-doped phosphor will emit a narrower emission spectrum band (half-wave width =23nm), peaking at 506nmgreen light) when excited by 254nm or 304nm. When monitored at 506nm, it shows an absorption spectrum with main peak at 304nm. Based on the peak of emission spectrum fall at 506nm, the luminescent transition matches the spin-forbidden transition, 4T1(4G)→6A1(6S). Co2+-doped phosphor will emit a red light, peaking at 660nm when excited by 254nm or 642nm. When monitored at 660nm, it shows an absorption spectrum with main peak at 642nm. Based on the peak of emission spectrum fall at 660nm, the luminescent transition matches the spin-allowance transition, 4T1→4A2(4F). Cr3+-doped phosphor will also emit a red light, main peak at 697nm when excited by 254nm or 589nm. As affected by a weak spin-orbit coupling, it generates a weak electronic vibration thus presenting a diversified linear emission spectrum. When monitored at 697nm, it shows a broad absorption spectrum with two main peaks at 434nm and 589nm, respectively. The luminescent character of doped Ni2+ or Fe3+ phosphors is not practical while Fe3+ will emit very weak emission spectrum, peaking at 725nm and Ni2+ has no characteristics for emission by its nature. When the concentration of doped 3d transition metal ions becomes too high, it will result the loss of partial excitation energy caused by the exchange relaxation or excitation energy transfer of their resonance transfer. Consequently, the concentration quenching reduces its intensity of emission or even with no emission.
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Tung, Ming-Chung, and 童明駿. "Preparation And Characterization Of Silicate Phosphors." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/14105678634908381795.
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碩士國立高雄海洋科技大學
微電子工程研究所
100
In this study, calcium silicate phosphor was prepared by Sol-gel methods, and then calcined at a temperature of 600-900℃ for 2hr. The as-obtained calcium silicate phosphor was characterized by photoluminescence spectrum, X-ray diffraction pattern and scanning electronic microscopy. Calcium nitrate powder to add multiple and then prepared at 100 °C for 2hr and calcined at 600 °C for 2hr by Sol-gel method. The fluorescence excited by a He-cd Laser line of 325 nm, revealed blue-white emission bands at 481 nm (4F9/2→6H15/2) and 573 nm (4F9/2→6H13/2). The roles of Dy3+ in the calcium silicate phosphor were examined. It is found that the fluorescence characteristics of dependent on Dy3+ ions. With more Dy3+, the fluorescence intensity is decreased.
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CARRASCO, RUIZ IRENE. "Fast emitting oxide scintillators and phosphors." Doctoral thesis, 2017. http://hdl.handle.net/11562/956665.
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In questa tesi sono stati preparati vari materiali luminescenti ed è stata eseguita la loro caratterizzazione strutturale e spettroscopica per testare la loro possibile applicazione come fosfori e/o scintillatori. I campioni studiati sono materiali policristallini a base di ossidi (silicati e fosfati) drogati con diversi tipi di ioni lantanidi. Sono state studiate le proprietà di lumenescenza di Tb3+ e Eu3+ a temperatura ambiente e le loro evoluzioni nell’intervallo di 8-300 K, in vari silicati a base di Tb con una struttura di tipo silico-carnotite. Nel caso di Ca3Tb2 xEuxSi3O12 è stato osservato un efficiente trasferimento di energia Tb3+ Eu3+ a seguito di eccitazione nell’UV. In Ca3Tb2Si3O12 e Ca3Tb2 xEuxSi3O12 è stata trovata una veloce migrazione di energia tra gli ioni Tb3+. È stata studiata anche un’altra diversa serie di composti con struttura silico-carnotite a temperatura ambiente. In questo caso, i campioni sono materiali a base di Gd e Y, drogati con Tb3+ e Eu3+. Il colore della emissione risultante di questi sistemi può essere modificato controllando il rapporto di concentrazione Tb3+/Eu3+, portando ad una emissione prossima al bianco nel caso di alcuni dei campioni analizzati. L’effetto dei cambiamenti strutturali della matrice sulla luminescenza del Pr3+ è stato studiato in due famiglie di fosfati. Nel caso delle polveri di Ca9M(PO4)7 (M = Al, Lu) è stato osservato che le proprietà ottiche delle transizioni 4f→4f del Pr3+ sono abbastanza insensibili alla natura del catione M, ma dipendono fortemente dalla quantitá di drogante: per un’alta concentrazione del Pr3+ l’emissione dal livello 1D2 è spenta a causa della presenza di processi di cross relaxation, mentre nessun cambiamento evidente è stato osservato nelle transizioni originate nel livello 3P0. Nel caso dei campioni K3Lu1-xYx(PO4)2:Pr3+, è stato trovato che l’emissione a seguito di eccitazone UV è dominata dalle transizioni intraconfigurazionali 5d→4f del Pr3+ e che l’aumento della quantità di Y causa uno spostamento della banda di emissione verso il blu. Questo spostamento è collegato ai cambiamenti strutturali indotti nella matrice a causa della sostituzione del Lu con Y. Eccitando con raggi X la favorevole sovrapposizione tra l’emissione dovuta ai difetti della matrice e le transizioni 4f→4f del Pr3+ provoca una progressiva variazione del rapporto tra le transizioni 5d→4f e 4f→4f.In this thesis, various luminescent materials have been prepared and their structural and spectroscopic characterization has been performed in order to test their possible application as phosphors and/or scintillators. The samples under study were oxide based polycrystalline materials (silicates and phosphates) doped with different lanthanide ions. The luminescence properties of Tb3+ and Eu3+ at room temperature and their evolution in the 8 330 K range have been studied in various Tb based silicates with silico carnotite type structure. In the case of Ca3Tb2 xEuxSi3O12, efficient Tb3+ Eu3+ energy transfer has been observed upon UV excitation. Fast energy migration among Tb3+ ions has been found in Ca3Tb2Si3O12 and Ca3Tb2 xEuxSi3O12. A different series of silico carnotite type compounds has been also studied at room temperature. In this case, samples were Gd and Y based materials co doped with Tb3+ and Eu3+. The resulting emission colour of these systems can be modified by controlling the Tb3+/Eu3+ concentration ratio, leading to close to white emission in some of the analysed samples. The effect of the structural changes of the host lattice on the luminescence of Pr3+ has been analysed in two families of phosphates. For the Ca9M(PO4)7 (M = Al, Lu) powders it has been found that the optical properties of the Pr3+ 4f→4f transitions are quite insensitive to the nature of the M cation, but depend strongly on the dopant content: at high Pr3+ concentration the emission from the 1D2 level is quenched due to the presence of cross relaxation processes, whereas no evident changes were observed in the transitions originated in the 3P0 level. In the case of K3Lu1-xYx(PO4)2:Pr3+ samples, it has been found that the emission upon UV excitation is dominated by the 5d→4f intraconfigurational transitions of Pr3+, and that increasing Y content causes the blue shift of the emission band. This shift is linked to the structural changes induced in the host lattice because of the substitution of Lu by Y. Upon X ray excitation the favourable overlap between the defect emission of the host and the Pr3+ 4f→4f transitions causes the progressive variation of the ratio between the 5d→4f and the 4f→4f transitions.
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Dahm, Kimberly Hockaday. "Luminescent properties of inorganic oxides." Thesis, 1994. http://hdl.handle.net/1957/35265.
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Fan-chiang, Chih-Shun, and 范姜智順. "Simple Modeling of Phosphors for Color Mixing." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/24519537945825637191.
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碩士國立中央大學
光電科學研究所
95
Before Since half a century ago, phosphor technology has been playing an important role in the applications of the general lighting and the display engineering both. However, the combination recipes of the color phosphors to goal at the target chromaticity ate still built up by the experiments of trials and errors. It is of great time-consuming and very inefficient. Therefore, how to quickly obtain the accurate weight ratios of phosphors in the combination recipes becomes a critical issue of phosphor technology for many practical applications. In this work, firstly the principle of the color mixing has been applied to the optical mixing ratios of phosphors in approaching to the target chromatic performance. Then, the relation between the optical mixing ratios and the weighting ratios is concluded to an experimental model from a great amount of the realistic datum. Finally, any requested chromatic performance of the phosphor recipe can be precisely predicted by these two steps above. As a result, the chromatic deviation from the quick model to the goal can be well controlled down to less than 0.003 (Δxy). It will also been tested in the practical CCFL production lines about the accurate phosphor mixing recipes.
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Lee, Chih-Ming, and 李志明. "The study of photoluminescence on SrAl2O4 phosphors." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/04624661844215197239.
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碩士國立臺北科技大學
材料及資源工程系碩士班
91
Red emitting SrAl2O4:Sm3+ phosphor has been synthesized by using solid reaction method. It was fired in an inert atmosphere. However, the emission spectrum of SrAl2O4:Sm3+ phosphors presented 3 spectra peak at 562,596 and 643nm,which matches the Sm3+ characteristic luminescent transition of 4G5/2 6H J (J=5/2,7/2,9/2). In comparing with adding 5wt% LiF and 5wt% B2O3 respectively to phosphor irregardedly of adding any concentration of activator, the SrAl2O4：Sm phosphor with addition 5wt% B2O3 has the better PL intensity. Besides, when changing the concentration of B2O3 in SrAl2O4：Sm phosphor and found that the SrAl2O4：Sm phosphor with addition 10wt% of B2O3 with the relative maximum PL intensity. In finding the relationship between the concentration of B2O3 and inter- planar spacing in host material, the concentration of B2O3 is strongly-linked with the spacing of the crystallographic plane (-211 ) but has not the direct relationship with planes (220) and (211) . The reason is that the B3+ ion replaces the Al3+ ion in (-211 ) plane and causes shrinkage of crystal lattice. The more shrinkage of the crystal lattice will produce more crystal defects and hence a stronger PL intensity.
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Ho, Kuang-Yu, and 何光宇. "Synthesis and Luminescent Properties of Ba3MgSi2O8 Phosphors." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/dr7d6n.
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碩士國立臺北科技大學
材料科學與工程研究所
99
This study is focused on the synthesis and luminescent properties of novel alkaline silicate phosphors. Conventional solid state reaction method is adopted to synthesize earth element-activated phosphors and co-doping phosphors. To synthesize Ba3MgSi2O8 host, we discuss the effect of different flux, flux concentration, firing temperture.In doping process the effect of different firing temperture, doping concentration and atmosphere on the luminescent properties is observed.Finally we try to make a EL device with Ba3MgSi2O8 phosphor we made. When we add 2wt% of H3BO3 and fireing temperture 1250°C, we will have Ba3MgSi2O8 with good emission property.The emission peaks of Ba3MgSi2O8:Eu3+ phosphor is originated from 5D0→7FJ(J=1,2,3,4) transitions, which show a orange-red color and are also independent of host lattice surroundings. And Ba3MgSi2O8:Eu2+phosphors show a 4f65d→8S7/2 transition with blue 442nm emission, which depends on the covalence and crystal field splitting effects of the host lattice.Due to sensitizer, Ba3MgSi2O8:Eu2+,Dy3+ have better emission intensity and long afterglow property. Ba3MgSi2O8:Eu2+,Mn2+ will show white color and show different color with different doping concentration. The EL device show emission intensity and we can use it in special situation.Based on excitation spectra analysis and UV-vis analysis ,the main excitation peaks of Ba3MgSi2O8:Eu3+ ,Ba3MgSi2O8:Eu2+ , Ba3MgSi2O8:Eu2+,Dy3+ and Ba3MgSi2O8:Eu2+,Mn2+ phosphors are located at ultraviolet region of the spectrum. Due to its high emission intensity, these phosphors possess potentials on UV-chip excited WLED applications.
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Yu, Kuo-Chang, and 游國彰. "Synthesis and Luminescence Properties ofAlkaline Silicate Phosphors." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/36586821488298028818.
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碩士國立成功大學
材料科學及工程學系碩博士班
94
Red phosphors applied in UV-LED is the one of the significant topicsrecently. In order to obtain the efficient phosphors, MSiO3:Eu3+ X mole% ( M=Mg, Ca, Sr, Ba；X=0~20 ) were synthesized via sol-gel method. Theeffects of calcination temperature, contents of Eu3+and Bi3+, conditions of re-heat treatment and hydrolysis of TEOS on the relative emission intensity of the phosphors were investigated. It had similar form for the emission spectra of MSiO3:Eu3+ ( M=Mg, Ca, Sr, Ba ). The emission intensity peaks are at 613 and 590nm while the MSiO3:Eu3+ ( M=Mg, Ca, Sr, Ba ) phosphors were excited by UV-LED ( λem=383nm ). However, it had higher emission intensity of MgSiO3:0.12Eu3+calcined at 800 oC, CaSiO3:0.12Eu3+ calcined at 1200 oC, SrSiO3:0.12Eu3+ calcined at 900 oC and BaSiO3:0.12Eu3+ calcined at 900 oC for 2h. In the study, the emission intensity of MgSiO3:0.12Eu3+ powders increased with raising the temperature of re-heat treatment。The phosphors had the highest emission intensity while controlling the re-heat treatment at 1000 oC、the condition of TEOS at 40 oC, pH=0.85。Doping 6mol% Bi3+ for the phosphors is also increasing the emission intensity.
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Lin, Chen Yu, and 陳昱霖. "Synthesis and characterization of Garnet (Y3Al5O12) phosphors." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/56932012825042562840.
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碩士國立成功大學
材料科學及工程學系
89
This research is to investigate the effect of various type of rare-earth and transition element activator（R3+）doping on the structural and luminescence properties of Y3Al5O12(YAG) phosphors. The effect of particle size of YAG phosphors on luminescence is also studied by solid state, coprecipitation, sol-gel and HMDS method respectively. The nano-scale with well crystalline and single phase powder of R-doped（R＝Ce、Sm、Gd、La、Cr）YAG was synthesized by heat treatment of HMDS treatment, first at 450℃ for 3 hours and then at 980℃ for 8 hours. The effect of sintering time and temperature on the purity of R-doped YAG were also investigated to determine the optimal preparation condition. The X-ray diffraction, EDS, SEM, TEM and FTIR were utilized in the characterization of phase purity and microstructure of phosphor nanoparticles. Photoluminescence（PL） spectroscopy was utilized to characterize the optical properties. The minimum grain size was found to be 0.8μm、56nm、43nm、32nm respectively, whereas the corresponding specific surface area was determined to be 1.70、23.58、31.04、37.25 m2/g for YAG phase synthesized by solid state, coprecipitation, sol-gel, HMDS treatment, respectively, In order to investigate the concentration effect of doping activator on spectral properties and color characteristics, we have prepared several series of （Y3-xR（1）x）Al5O12 and Y3（Al5-yR（2）y）O12（R（1）＝Ce、Sm，R（2）y＝Cr）（0≦x,y≦0.3）. The cell parameter（a0）of R-doped YAG as a function of activator concentration x, y were discovered to increase with increasing x, y. The intensity of luminescence emission for R-doped YAG phase was found to first increase with increasing activator R concentration（i.e.,x）, then reach a maximum and decrease as x further increases.Two series of （Y3-xLax）Al5O12：R and（Y3-xGdx）Al5O12：R（R＝Ce、Sm）（0≦x≦2.4）have also been prepared by systematic substitution of Y3+ by La3+ and Gd3+ to investigate the effect of host composition on the luminescent properties for these two series of phosphor nanoparticles.The CIE chromaticity coordinates for above phosphors were determined based on the corresponding PL spectra.
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Lee, Cheng-Tao, and 李承道. "Preparation and Characterization of Tin Oxide Phosphors." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/01999444522039001498.
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碩士國立臺灣大學
化學工程學研究所
96
Spherical Sn1-xO2: Sm phosphors were successfully synthesized via a microwave-assisted solvothermal route. A broad excitation band ascribed to the host absorption was observed at 318 nm. The prepared phosphors had several emission peaks at 560-700 nm assigned to f-f transition of Sm3+. The emission intensity of Sn1-xO2: Sm phosphors was increased with increasing the concentration of Sm3+ up to x = 0.9%. When the concentration of Sm3+ was further increased, the emission intensity was reduced due to the formation of an impurity phase. As the power of microwave increased, the particle size was reduced because of the increase in the number of nuclei. The luminescence intensity of the phosphors was slightly decreased with increasing the applied power due to an increase in surface defects. SnO2: Eu3+ phosphors were successfully synthesized via a microwave -assisted solvothermal route. The solvents used were found to have significant effects on the morphology and the luminescent properties of the obtained phosphors. Using ethanol as a solvent resulted in the formation of spherical phosphors with enhanced luminescent intensity. SnO2: Eu3+ phosphors exhibited a reddish-orange emission under excitation at 314 nm, and displayed a broad excitation band in the range of 240-370 nm due to the host absorption. In the microwave irradiation process, increasing the concentration of urea resulted in complete precipitation of Eu3+ ions, thereby enhancing the luminescent intensity.
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王明發. "Preparation and characterization of YAG phosphors particles." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/39691925087126466296.
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碩士南台科技大學
化學工程系
92
Cerium-doped yttrium aluminum garnet powder (YAG-Ce) could be synthesized by the precipitation method and followed by the calcinations process at low temperature. There were two different procedures for synthesize YAG-Ce in this article. The first procedure (A-Method) used the solution of ammonium carbonate solution as the precipitant which was titrated slowly into the metal complex dyes solution. In the second procedure (B-Method), the precipitant solution was switched to the metal complex dyes solution which was titrated into the ammonium carbonate solution. The precipitates of both the procedures were characterized by XRD、EDS、TEM and FTIR. As calcined at 900℃ for 1 hour, the final product of method A had not any impurity phase in its XRD pattern, but the final product of method B showed the impurities of YAP and YAM in its XRD pattern. The calcinations temperature should be higher than 1000℃ for the formation of pure YAG: Ce powder by method B. The fluorescing properties of the final products were characterized by PL spectrometer. The effect of the calcinations temperature and the amount of adding rare earth element to the property of the red shift and blue shift of powders had been studied. In 900℃, the fluorescent brightness of the powder formed by method A is brighter than that of method B. The maximum excitation wavelength of the method A powder is 470 nm,with the emission wavelength of 535nm. The brightness of these powder was increased by increasing the formation temperature.
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Liu, Wei-Wei, and 劉瑋瑋. "Thermal effect on phosphors applied in LEDs." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/44091542626589255091.
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碩士國立中央大學
光電科學研究所
99
The heat was inevitably generated from chips when light-emitting diodes (LEDs) were driven at working current. The quantity of heat affects the characteristic of phosphors. This thesis devoted to study the thermal effect on different kinds of phosphors that are commonly used in LEDs. This study establish an experimental setup and procedures which was analyzed its tolerance to derive this phenomenon. Except for measuring the shift in spectrum and thermal degradation in phosphors, this study also vary distinct parameters such as concentration, thickness, and particle numbers to study the correlation between the optical properties. It is possible to anticipate the optical performance when combining the luminescent behaviour of phosphor under thermal aging to provide accurate proposition in the future.
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Lee, Cheng-Tao. "Preparation and Characterization of Tin Oxide Phosphors." 2008. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1507200811141500.
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Huang, Kuan-Wei, and 黃冠維. "Activator Controlled Phosphors for Light-emitting Diodes." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/56378003332950216653.
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碩士國立臺灣大學
化學研究所
100
Light-emitting diodes (LEDs) have received wide attention in the recent decade owing to their high brightness, long lifetime, environmental friendliness and small size. The conventional means of generating white light in white LEDs combine of phosphor layer with UV- or blue-LEDs that converts the initial radiation into a complementary color. The development of new phosphor is of priority concern in LED-driven applications. The development of new phosphor is limited in try-and-error method. When the incorporation Eu exist in Eu3+ state, comparing the broad band photoluminescence in Eu2+, the line emissions in Eu3+ activated phosphor is less applicable for LED-pumped white light. In this study, we therefore provide a crystal based method approach for developing phosphors. The proposed approach is successful demonstrated in the new phosphor Ca12Al14O32F2:Eu3+. By using of Si4+–O2- to replace Al3+–F- and Eu3+ is therefore able to reduce to Eu2+, which can provide broadband emissions. Combinatorial studies with synchrotron X-ray diffracrion (XRD) refinement, X-ray absorption near-edge structure (XANES), high resolution electron microscope (HRTEM) and solid state nuclear mangetic resonance (NMR) help to understand how the dopant affects the crystal structure and photoluminescence. The results were agreed well with the proposed mechanism of crystal variation in our study. We also report a novel phosphor series Li5La3M2O12:Re3+ (M = Nb, Ta; Re = Pr, Sm). The XRD refinement is adopted to characterize the variation of lattice. Based on the results of low temperature photoluminescence measurement and time-resolved spectrum, the transition mechanism of Pr3+ analogue is therefore proposed. The Pr3+ analogue exhibits multiband emission within bluish-green and red range, and can serve as a candidate for blue-LED. In addition, the Sm3+ analogue exhibits red luminescence upon UV light excitation, showing that can apply in UV-LED related applications.
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Chen, Wei-Ting, and 陳韋廷. "Structure and Optical Properties of Oxynitride Phosphors." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/79533519568174584522.
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博士國立臺灣大學
化學研究所
101
This study focuses on the development of an effect of cation-size mismatch strain between the dopant (activator) and substituted objective (cation in host lattice). Several chemical tunings have been reported; however, their underlying mechanisms remain unclear. In addition, these chemical tunings invariably shift the energy in a group of comparable materials in the same way, e.g., a consistent red shift. Our materials, M2Si5-xAlxN8-xOx:Eu (M = Ca, Sr, Ba), show a large red shift for M = Ba and a small red shift for Sr, but exhibit a large blue shift for Ca. Thus, we propose a mechanism for this size mismatch tuning based on local nitride/oxide anion clustering and supporting evidence. Thermal quenching of photoluminescence is also tuned by cation mismatch, Moreover, both effects are important for light-emitting diode (LED) devices, and both mismatch tuning effects are explained by our size-driven anion clustering model. In the second part, an unreported phenomenon for tuning the emission properties of Tb3+ activators is discussed. Our material, Ba2.89Si6O12N2:Tb0.11, shows the tunable and reversible properties in the green/blue emission under UV to VUV radiation excitation. Thus, we propose a possible mechanism for this color reversal control based on a specific transition route as a color-tunable switch at the UV/VUV range and supporting evidence. This effect is significant for Tb-activated phosphors in PDP or fluorescent lamp devices, and the color-reversal effect is explained by our configurational coordinate model. In the third part, we develop a highly efficient green phosphor for using in a practical UV-LED device. The highly efficient Ba3Si6O12N2:RE (RE = rare earth metal) is composed of single-doped and co-doped phosphors with Eu and Ce rare earth metals. The possible mechanisms of the two important photoluminescence properties are proposed for LED device-used phosphors, namely, (1) spectral shift in a high temperature environment in the Eu-doped phosphor and (2) highly efficient transfer property in the Ce/Eu co-doped analogue. The UV-WLED device is fabricated by green Eu-doped Ba3Si6O12N2 and other blue and red phosphors. The distinctive properties of this oxynitride parent structure make it an interesting subject for research and as a candidate for a blue/green component for UV-LED applications.
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Kuo-ChingCheng and 鄭國清. "The Synthesis of Silicate Phosphors for Near Ultraviolet Excitation and Application of Phosphor Films for Replaceable White LED." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/66674523212508314978.
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碩士國立成功大學
電機工程學系
104
In this study, BaZr1-yHfySi3O9: Eu2+ and Li2SrSi1-yTiyO4: Eu2+ silicate phosphors were synthesized by the solid-state reaction method, which could be well excited by near-ultraviolet (UV) light. Using near-UV light-emitting diode (LED) chip to excite cyan and yellow color phosphors was a feasible way to generate white light. However, due to higher operating temperature for UV-LEDs, phosphors with better thermal stability became crucial. Thus, this work focused on improving the thermal stability and the luminous intensity. The thermal stability of the former was improved with increasing the concentration of Hf4+ ions. T50 value (the temperature at which the emission intensity falls to 50% of that at room temperature) was enhanced from 230 to 281 °C. Besides, the emission intensity of the latter was enhanced 14.15% by doping Ti4+. Because of their broad excitation spectra, these phosphors could be applied on the near-UV LEDs to form the phosphor-converted white LEDs (pc-WLEDs). The thermal stability of BaZr1-yHfySi3O9:Eu2+ phosphors enhanced due to the substitution of Zr4+ by Hf4+ ions, which affected smaller lattice vibrations by phonons from heating. Therefore, the activation energy was increased from 0.374 to 0.3832 eV, reducing the probabilities of non-radiative reaction. However, due to the doping of Hf4+, the emission intensity decreased apparently with the increasing concentration of Hf4+ with impurity phase.Finally, NH4Cl was added to raw material as flux and promoted the crystallization reaction. The optimal concentration of NH4Cl was found to be 6 wt%. Besides, Li2SrSi1-yTiyO4: Eu2+phosphors were doped by Ti4+, which leads to larger crystallite size, from 65.71 to 70.47 nm. The optimal concentration of Ti4+ was 2 mol% and the emission intensity could depend on the crystallite size. For the WLED application, BaZr1-yHfySi3O9:Eu2+ cyan phosphors and commercial (Ba, Sr, Ca)2SiO4:Eu2+ yellow phosphors were combined with near-UV-LEDs (λex=395-400 nm) to generate white light. In the past, the conventional dispensing technology was directly coating on chip. In this study, the reflector cup was combined with phosphor films to form replaceable white LEDs. It takes significant advantages for practical applications such as detachable, low-cost, and one LED with various parameters for characteristics of white LED. By modulating number of different pieces of phosphor films, it is suitable to find the optimal characteristics of the white LEDs. The optimum luminous efficiency, CIE coordinates, and CRI of the final proposed devices were 20.9158 lm/W, (0.325, 0.358), and 80.47, respectively.
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Cheng, Yu-Chih, and 鄭有志. "Synthesis and Luminescence Properties of Y2O3:Eu3+ Phosphors." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/69429461387564973643.
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碩士國立成功大學
材料科學及工程學系碩博士班
92
To improve the photoluminescence properties of red emission phosphors used for 383 nm UV-LED Y2O3:Eu3+ powders were synthesized by solid state and sol-gel methods. Effects of the contents of Eu2O3 & SiO2 and calcining parameters on the phosphors crystallization, particle size, shape and photoluminescence properties were investigated. Y2O3:Eu3+ phosphor powders synthesized by solid state and sol-gel methods and then calcined at 1500℃for 4 h, show the absorption and emission behavior under excitation source around 360-420 nm UV-light. The phosphor shows the strongest emission peak at 612 nm when the excitation source is 395 nm. The Y2O3:Eu3+ (Eu3+=1~20 mole%) phosphors synthesized by solid state and sol-gel method then calcined at 1100~1500℃ for 4 h both show one phase of Y2O3. Its relative emission intensity (at 612 nm) increases with calcining temperature and Eu3+ dopants. It shows the strongest emission intensity when 19 mole% Eu3+ doped in Y2O3 phosphor powder. 4~10 wt% of SiO2 additions increase the relative emission intensity of (Y0.91Eu0.09)2O3 phosphor powder. Y2O3:Eu3+ phosphor powder synthesized by sol-gel method shows better relative emission intensity, relative Q. E. and absorption efficiency than powders synthesized by solid state method.
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Tang, Tzu-Piao, and 唐自標. "Preparation and Characterization of Zinc Sulfide based Phosphors." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/94479935143596786583.
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博士大同工學院
材料工程研究所
87
The objective of this paper is to discuss the preparation of ZnS phosphor powder and their firing atmosphere. In this research, several controlling factors that could affect the phosphor''s luminescence characteristics, such as firing temperatures, atmosphere, firing time and the selection of flux and dopant, were evaluated. When prepare the ZnS phosphor powder using solid-reaction firing, it is important to control the distribution of additives. However, the luminescence characteristics of ZnS is dependent upon the firing atmosphere, temperature and time. It is found that the luminescent property of host lattice changes along with amount of hexagonal phase in ZnS phosphors. The higher the firing temperature, the higher the amount of hexagonal phase can be found in ZnS phosphor. Also, its wavelength will shift toward long wavelength region (449nm R453nm) with higher luminescent intensity. For those content less hexagonal phase, its wavelength will move toward short wavelength region (459nmR 457nm) with lower luminescent intensity. After washing with water, the wavelength of ZnS phosphor will shift to short wavelength region (449nm) and shows better luminescent effect and higher intensity. Blue ZnS phosphors with (Ce) dopant can be formed in inert atmosphere and is known as 5dR4f host lattice luminescence. With the addition of flux, its luminescence increase and wavelength is in the ranges between 446nm-480nm. After washing, the higher the Ce residue in ZnS phosphors, the better the luminescence. But, the remained Chlorine and Sodium were also reduced and affect its luminescence. For ZnS phosphors formed at higher temperature, the loss of Ce can be reduced after washing, and thus, help the formation of defect and amount of ions. Under the equivalent of ionic hole and number of ions, it will increase the luminescence intensity. It was found that ZnS phosphor has the highest luminescence intensity when firing at 950℃ with 0.2 Ce mol% addition. Red ZnS phosphors were fired under reducing atmosphere with the addition of Sm+3. ZnS host lattic self-activation luminescence center was found disappeared under reducing condition. When Sm2O2S exists, it has better Sm characteristic luminescence due to Sm ions transfer between 4f-4f orbital and move from 4G5/2 to 6H5/2、6H7/2、6H9/2. If the stable Sm2O3was formed, the self-activation luminescence center will appear. The role of the addition of flux (LiCl) can determine the exciting energy transformation (photoionization) which will then result in either self-activation or Sm characteristic luminescence. A certain amount of LiCl addition can react with Sm compound and increase luminescence intensity. The optimal conditions to form ZnS phosphors with red characteristic luminescence is found at 1050℃ reducing atmosphere and LiCl：2.0 mol％，Sm +3：0.30mol%. The Tb characteristic luminescence was not found in ZnS phosphors when firing under reducing atmosphere with the additon of Tb. This is believed to be due to the Tb characteristic luminescence can only be emitted from5D4→7F6（487nm）、7F5（546nm）、7F4（588nm）、7F3（617nm）green luminescent materials. In order to produce Tb characteristic luminescence, the Tb need to be evenly distributed with the addition of flux. The optimal conditions for this process are 1050℃ firing temperature, reducing atmosphere, 0.5mol% of Tb and KF which is found need to be added three times as much as Tb.
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Yan, Jia-Hung, and 顏嘉宏. "Synthesis and Luminescence Characteristics of LaPO4:Tm3+ Phosphors." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/68hpmu.
Full textAbstract:
碩士國立高雄應用科技大學
電子工程系碩士班
101
This thesis is mainly composed of four subjects: (1) the preparation parameters of doping concentration, calcination temperature, and calcination time were optimized in order to achieve high efficiency of La1-xPO4:xTm3+ phosphor by co-precipitation method; (2) influence of the luminescence characteristics of the phosphor was investigated via co-doping Al3+ ions; (3) surface properties of the phosphors were modified by coating with carbon nanotubes (CNTs), which led to the improvement on phosphor conductivity and enhancement on the cathodoluminescence (CL) intensity of the LaPO4:Tm3+ phosphor; (4) white-light emitting devices were fabricated using the white phosphors, which from the optimal parameters to mix the multi-colored phosphor with doped Eu3+ ions. We found that the maximum luminescence intensity was achieved when the LaPO4:Tm3+ phosphor was synthesized with 3 mol% of Tm3+ using co-precipitation method and calcined at 1200°C for 2 h. As the energy-absorption peak for the Tm3+ was at wavelength of 357 nm, the LaPO4:Tm3+ phosphor excited with wavelength 357 nm led to the blue-light emission, with the strongest radiation peak at wavelength of 454 nm attributing to the 1D2 → 3F4 of Tm3+ as well as a color purity reaching 92%. In addition, luminescence measurements showed that it was not only the photoluminescence intensity been improved significantly via co-doping ions but also the CL intensity could be effectively increased by coating with CNTs. For the synthesis of white-light phosphor, the red Eu3+ with different concentrations was co-doped. It was found that the luminance at wavelength of 454 nm gradually decreased; on the contrary, reddish-orange emission at wavelength 594 nm was strengthened. The maximum red luminescence intensity was obtained when 7 mol% of Eu3+ was doped. Obviously, energy transfers between Tm3+ and Eu3+ occurred. As a result, white-light emission was observed. Furthermore, the electroluminescent (EL) devices were prepared by screen printing; the EL properties were measured and discussed in the last section.
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Yeh, Cheng-En, and 葉承恩. "Ce3+- Doped Yttrium Aluminum Garnet Glass-Ceramic Phosphors." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/zsgs8c.
Full textAbstract:
碩士大同大學
材料工程學系(所)
102
Yttrium aluminum garnet (Y3Al5O12, YAG) crystal has high mechanical strength, transparency, chemical stability, thermal conductivity, and can provide a good crystal-field environment to activated ions. In the present project, Ce3+-doped YAG-containing glass-ceramic will be investigated for its application in W-LEDs. In the present project, parent glasses based on the composition of Y2O3 –Al2O3 –SiO2 –CeO2 will be prepared by melt-quench method. After crystallization heat-treatment 1450℃/2-6h, glass-ceramics containing Ce3+-doped YAG crystalline particles embedded within silicate glass matrix will be formed by SEM/EDS. The YAG crystalline phase formed in the glass will be identified by XRD. The photoluminescence and CIE color coordinate locus of the Ce3+-doped glass-ceramics will be examined. With the more YAG crystalline formed (more heating temperature or time), the samples show more bright yellow and the yellow light strength more strong. Finally, the color coordinate of the LED composite containing a Ce3+-doped YAG glass-ceramic plate and a blue LED chip will be measured. These result to assess the feasibility for YAG glass-ceramics application in the W-LEDs.