Wyniki wyszukiwania - Biblioteka Nauki

1

Luminescence Properties of CaAl₂O₄:Eu³⁺, Gd³⁺ Phosphors Synthesized by Combustion Synthesis Method

100%

Verma N. , Singh K. , Marí B. , Mollar M. , Jindal J.

Acta Physica Polonica A

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2017

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tom 132

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nr 4

1261-1264

EN

CaAl₂O₄:Eu³⁺ (1 mol.%) co-doped with varying concentration of Gd³⁺ (1, 2, 5, and 10 mol.%) were prepared by combustion synthesis method at 600°C and further annealed at 1000°C. All the compositions were investigated for their structural and photoluminescence properties. It was observed that both states of europium i.e. Eu³⁺ and Eu²⁺ were present and ratio of these states changes on heating at 1000°C. The materials synthesized at 600°C showed high intense peak around 440 nm due to presence of Eu²⁺ and less intense peaks in the red region which were due to presence of Eu³⁺. On annealing the compounds at 1000°C, intensity of peak around 440 nm decreases and intensity of peaks in the red region increases significantly. The ⁵D₀ → ⁷F₃ transition due to Eu³⁺ at 657 nm appears as the highest intensity peak. All co-doped samples annealed at 1000°C showed the higher intensity than the mono doped sample which is due to energy transfer from the Gd³⁺ to Eu³⁺. The second rare-earth ion (Gd³⁺) acts as sensitizer and enhances the photoluminescence intensity. The X-ray diffraction spectra reveal the monoclinic phase of CaAl₂O₄ in all the samples which showed that Eu³⁺ and Gd³⁺ do not change the crystalline structure of calcium aluminate.

2

On the thickness of phosphor coating in fluorescent lamps and its impact on selected light parameters

100%

Różowicz A.

Electrical Power Quality and Utilisation. Journal

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2005

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tom Vol. 11, nr 1

45-48

EN

This article presents the results of research carried out on the formation of light parameters of the phosphor coatings and surfaces of fluorescent lamps. Particular attention has been paid to those parameters which influence the formation of light parameters such as light efficacy and ripple. The results of the measurements of light efficacy and light ripple are given in terms of the thickness of coatings and some of the physical parameters of phosphors used in AC powered mains frequency fluorescent lamps. On the basis of attained results the conclusions are given concerning the efficacy of light and the depth of light ripple in the function of the thickness of phosphor coating.

3

Red-emitting LiEuW2O8 phosphor for white emitting diodes prepared by sol-gel process

100%

Hwang K. S. , Jeon Y. S. , Hwangbo S. , Kim J. T.

Optica Applicata

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2009

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tom Vol. 39, nr 2

375-382

EN

Scheelite-type LiEuW2O8 (LEW) phosphors with the optical function of color conversion from near-UV to red were prepared by sol-gel method using a lithium acetate dehydrate, europium(III) nitrate pentahydrate, and tungsten(VI) chloride as starting materials. Viscous mixing sol was prefired at 300 °C for 120 min in air and then white powder precursor was finally annealed at 500-800 °C for 240 min in Ar. From an X-ray diffraction analysis, all the samples are isostructural and belong to the tetragonal system of scheelite-type. The main emission peak is 5D0 › 7F2 transitions of Eu3+ at 615 nm, other transitions from the 5D0 › 7F1, 5D0 › 7F3 and 5D0 › 7F4 located at 570-700 nm range are weak. The characteristic emission of WO4-2 in LEW is quenched absolutely and only red-light emission of Eu3+ appears. Crystallinity, surface properties and red-emission by near-ultraviolet (395 nm) were improved by high-temperature annealing.

4

Luminescent properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ particles as a potential bluish green phosphor for ultraviolet light-emitting diodes

100%

Yao S. , Chen D.

Open Physics

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2007

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tom 5

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nr 4

558-569

EN

In our study, the 1% mol Eu2+ doped Li2CaSiO4: B3+ phosphors were prepared by the combustion method as fluorescent material for ultraviolet, light-emitting diodes (UV-LEDs) used as a light source. The properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ phosphors with urea concentration, doping boric acid and a series of initiating combustion temperature were investigated. The crystallization and particle sizes of Li2 (Ca0.99, Eu0.01) SiO4: B3+ has been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by UV to the visible region, and exhibited bluish green light with a peak of 480 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li2 (Ca0.99, Eu0.01) SiO4: B3+ and the optimum molar ratio of boric acid to calcium nitrate was about 0.06. The optimized phosphors Li2 (Ca0.99, Eu0.01) SiO4: B0.063+ showed 180% improved emission intensity compared with that of the Li2 (Ca0.99, Eu0.01) SiO4 phosphors under ultraviolet (λex =287 nm) excitation.

5

Effect of flux compounds on the luminescence properties of Eu3+ doped YBO3 phosphors

100%

Rafiaei S. M.

Materials Science Poland

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2016

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tom Vol. 34, No. 4

780--785

EN

In this investigation, Eu3+ doped YBO3 phosphors were synthesized by conventional solid state method at 1100°C under atmosphere condition. Meanwhile, different amounts of LiCl, BaCl2 and CaCl32 were used as the flux compounds to modify the morphology of the phosphor particles and also final luminescent properties. It was concluded that even small amounts of fluxes play a vital role in the growth of particles. Then the emission and excitation photoluminescence spectra were measured respectively at λexc = 240 nm and λem = 610 nm and it was found that using 2 wt.% of flux compounds has a significant influence on the emission intensity of YBO3 phosphors.

6

Combustion synthesis and luminescent properties of green-emitting phosphor (Sr, Zn) Al2O4: Eu2+, B3+ for white light emitting diodes (WLED)

100%

Yao S.-S. , Li Y.-Y. , Chen D.-H. , Tang W.-J. , Peng Y.-H.

Open Physics

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2009

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tom 7

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nr 1

96-101

EN

In this study, the phosphors (Sr1−x , Znx)0.9(Al2−y , By)O4 doped 10 mol % Eu2+, were prepared by combustion method as the fluorescent material for white light emitting diodes (WLEDs), performing as a light source. The luminescent properties were investigated by changing the combustion temperature, the boron concentration, and the ratio of Sr to Zn. The luminescence, crystallinity and particle morphology were investigated by using a luminescence spectrometer, X-ray diffractometer (XRD) and transmission electron microscopy (TEM), respectively. The highest intensity of Sr0.9(Al2−y , By)O4: Eu0.12+ phosphor was achieved when the combustion temperature was 600° and the concentration of B3+ was 8 mol % of the aluminate. A new blue emission was observed when the high Zn concentration (x ⩾ 0.8), and this blue emission disappeared with the Zn concentration became lower than 0.8. The combustion method synthesized phosphor (Sr0.6, Zn0.4)0.9(Al1.92, B0.08)O4: Eu0.12+ showed 3.3 times improved emission intensity compared with that of the Sr0.9(Al1.92, B0.08)O4:Eu0.12+ phosphor under λex = 390 nm.

7

Effect of Polymer Cations on Photoluminescence Properties of Blue Emitting Alkaline-Earth Metals and Silicon Based Phosphors

100%

Rahman M. , Kida T. , Nagano M. , Khan M.

Polish Journal of Chemistry

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2007

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tom Vol. 81, nr 2

249-255

EN

Efficient blue emitting phosphors were prepared by depositing mixed hydroxides of Ca, Sr, Ba, Mg, Eu over spherical SiO2 particles from tetra-ethyl-orthosilicate (TEOS) pre-coated with polycations (polyethyleneimine: PEI) followed by calcination at 1200C in a reducing atmosphere. The prepared phosphor showed intense blue emission, which can be ascribed to 4f 7-4f 65d interconfiguration transitions of Eu2+ ions. In contrast, the luminescence intensity of the phosphor was much decreased when prepared without polycations. It was suggested that negatively charged hydroxides are deposited on positively charged SiO2 surfaces pre-coated with polycations through electrostatic self-assembly interaction. The common formula of the prepared phosphors is AMgSi2O6:Eu2+ (A= Ca, Sr, Ba or fraction of Ca and Sr), where alkaline-earth/Si = 1, the each entire sample was prepared by treating with polycations and without polycations.

8

Functional materials produced on an industrial scale

88%

Barska J. , Kłysz S.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2015

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tom nr 36

19--30

EN

The article presents a wide range of applications of functional materials and a scale of their current industrial production. These are the materials which have specific characteristics, thanks to which they became virtually indispensable in certain constructional solutions. Their basic characteristics, properties, methods of production and use as smart materials were described.

9

Separation of rare earth elements from the leaching solution of waste phosphors by solvent extraction with Cyanex 272 and its mixture with Alamine 336

88%

Xing W. , Lee M. S.

Physicochemical Problems of Mineral Processing

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2020

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tom Vol. 56, iss. 1

184--194

EN

Waste phosphors contain rare earth elements (REEs) such as yttrium (Y), europium (Eu), cerium (Ce), terbium (Tb) and lanthanum (La). Separation of these REEs from the leaching solution of waste phosphors was investigated by solvent extraction with single Cyanex 272, binary mixture (mixture of Cyanex 272 and Alamine 336), ionic liquid (prepared by Cyanex 272 and Aliquat 336) in kerosene. The effect of solution pH and extractants concentration was mainly investigated. The results indicated that Y(III) was selectively extracted by single Cyanex 272 over the other four REEs from the HCl solution with initial pH range from 3 to 5. Synergistic extraction with the binary mixture was enough for the extraction of Y(III), Tb(III) and Eu(III) with a small amount of Ce(III). Scrubbing with pure Y(III) solution with intermediate acidity was effective in scrubbing Ce(III) from the loaded binary mixture organic phase. Stripping behavior of the Y(III), Tb(III) and Eu(III) by HCl solution was similar to each other. Tb(III) and Eu(III) can be separated by extraction with the binary mixture followed by scrubbing with pure Tb(III) solution. McCabe-Thiele diagrams were constructed for the extraction of Y(III) by single Cyanex 272 and that of Tb(III) by the mixture. A process was proposed for the separation of REEs from the leaching solution of waste phosphors by solvent extraction.

10

Tętnienie światła lamp fluorescencyjnych zasilanych napięciem przemiennym o różnych częstotliwościach

75%

Różowicz A.

Jakość i Użytkowanie Energii Elektrycznej

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2004

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tom T. 10, z. 1/2

91-95

PL

W artykule podano podstawowe informacje dotyczące zagadnień konwersji energii elektrycznej na energię świetlną. Wskazano parametry, które mogą wpływać na kształtowanie się parametrów świetlnych. Przedstawiono wyniki pomiarów współczynnika tętnienia w funkcji temperatury barwowej kilku grup lamp fluorescencyjnych zasilanych napięciem przemiennym o różnych częstotliwościach. Na podstawie otrzymanych wyników podano wnioski dotyczące głębokości tętnienia w funkcji temperatury barwowej i częstotliwości napięcia zasilającego.

EN

The basic information of conversion of electrical energy to light energy in article were passed. It parameters which were showed was they can influence on be shaping light parameters. The results of measurements were introduced the coefficient of pulsation in function of colour temperature of several groups of fluorescent lamps reinforced with alternating voltage about different frequencies. On base received of results on gave the conclusions the relating depths of pulsation in function of colour temperature and frequency of voltage feeding.

11

Effect of AlF3 and H3BO3 fluxes on the structure and optical properties of Ca-α-SiAlON:Eu2+ phosphor powders

63%

Pawlik T. , Michalik D. , Sopicka-Lizer M. , Lisiecki R.

Inżynieria Materiałowa

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2016

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tom Vol. 37, nr 1

35--40

EN

The continuous increase in demand for electric power necessitates constant search for new energy-efficient and economical light sources. One of them are light-emitting diodes (LEDs), requiring further development of materials enabling generation of warm white light that could replace the conventional light sources used so far. Problems related to the use of white LEDs include relatively low efficiency and light quality. A material that is currently a subject of interest due to its optical properties is Eu2+ doped Ca-α-SiAlON. It is regarded as one of the materials that can potentially be used as a yellow phosphor in white LEDs. The broad emission spectrum of Ca-α-SiAlON:Eu2+, bearing similarities with YAG:Ce3+ emission, is characterized by an emission peak maximum located in the wavelength range of 570÷585 nm, which enables obtaining a high colour temperature of a white LED. This study investigates the effect of addition of 1÷5 wt % AlF3 and H3BO3 as fluxes on the optical properties of phosphors obtained at different temperature. The syntheses were conducted in the temperature range of 1450÷1650°C in an N2/CO atmosphere. On the basis of the examination of the powder phase composition (by XRD), morphology, and chemical composition in microareas (by SEM/EDS), and the comparison of the emission spectra of the Ca-α-SiAlON:Eu2+ powders with a different flux content, it was found that the addition of AlF3 had a positive effect on emission intensity and quality.

PL

Celem pracy była ocena wpływu dodatku topników AlF3 oraz H3BO3 w ilości 1÷5% mas. na strukturę oraz właściwości optyczne luminoforów sialonowych domieszkowanych Eu+2, otrzymywanych w różnych temperaturach. Materiały te wykazują lepsze w porównaniu ze stosowanymi obecnie luminoforami na bazie YAG:Ce3+ właściwości optyczne. W związku z tym stają się potencjalnym materiałem na luminofory konwertujące pierwotne promieniowanie niebieskie lub z zakresu UV w nowych rozwiązaniach białych diod LED (wLED).

12

Sprawność konwersji w luminoforach YAG:Ce współpracujących z emiterami półprzewodnikowymi z zakresu UV-VIS

63%

Prorok M. P.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2017

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tom T. 7, nr 2

74--77

PL

Powszechnie stosowana metoda emisji światła białego wykorzystująca technologię LED-ową opiera się na użyciu luminoforu oraz emitera półprzewodnikowego z zakresu długości fali 440–460 nm (barwa niebieska). W wyniku zjawiska fotoluminescencji luminofor oparty na krysztale YAG-u z domieszkami ceru emituje szerokie spektrum z zakresu widzialnego o barwie zielonożółtej. Promieniowanie będące wynikiem fotoluminescencji, mieszając się ze źródłem wymuszającym daje barwę białą o temperaturze barwowej zależnej od typu luminoforu. W artykule przeprowadzone zostały badania dotyczące zarówno sprawności konwersji samego luminoforu jak i odpowiedzi spektralnej na niededykowane wymuszenie zrealizowane emiterami półprzewodnikowymi.

EN

Commonly used white light emmision method utilizing LED technology depends mostly on luminophore and wavelenght 440–460 nm (blue) semicondutor emiter use. Emission of the wide visible spectrum, greenish yellow in colour, is an effect of fotoluminescence in cerium doped YAG cristal based luminophore. As the effect of fotoluminescence, radiation interferes with source radiation, resulting in white colour light with colour temperature depending on luminophore type. The article presents the research on both conversion efficency of the luminophore and the spectra response for the nondedicated forcing, realised by usage of semiconductor emitters.

13

Charakterystyki wzbudzeniowo-emisyjne nanometrycznych proszków tlenku cyrkonu domieszkowanych jonami itru, europu i prazeodymu

51%

Mierczyk Z. , Kałdoński G. , Mierczyk J. , Łojkowski W. , Fidelus J. D. , Opalińska A.

Biuletyn Wojskowej Akademii Technicznej

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2011

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tom Vol. 60, nr 1

7-14

PL

W pracy przedstawiono wyniki badań materiałów luminescencyjnych na osnowie dwutlenku cyrkonu, domieszkowanych jonami itru, europu i prazeodymu, przeznaczonych do nowoczesnych półprzewodnikowych źródeł światła białego. Przeprowadzono pomiary charakterystyk wzbudzeniowo-emisyjnych i wyznaczono podstawowe parametry optyczne luminoforów.

EN

In this paper we focus on high-impact luminescence of Eu²⁺ or Pr²⁺doped ZrO₂ nanocrystals stabilized by Y₂O₃. As a class of inorganic luminescent phosphor, wide-band gap ZrO₂ has received considerable attention because of its utility for existing and future optoelectronic devices as a suitable host for rare-earth ions. In the article were gathered Exciting-emitting spectra of nanocrystals obtained by the hydrothermal microwave-driven process are presented. All investigated characteristics indicate the usability of studied materials as red luminescent phosphors.