Wyniki wyszukiwania - Biblioteka Nauki

1

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.

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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.

2

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.

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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.

3

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

100%

Różowicz A.

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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.

4

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.

5

Tętnienie światła lamp fluorescencyjnych zasilanych napięciem przemiennym o różnych częstotliwościach

75%

Różowicz A.

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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.