A Review of the Efficiency of White Light (or Other) Emissions in Singly and Co-Doped Dy3+ Ions in Different Host (Phosphate, Silicate, Aluminate) Materials.

In this review we will present several research papers pertaining to white colour (or other) emission from Dy3+ doped and undoped phosphor materials. The search for a single component phosphor material that could deliver high quality white light under UV or near UV excitation is an area of active research for commercial purposes. Amongst all rare earth elements Dy3+ is the only ion that could deliver simultaneously blue and yellow light under UV excitation. In optimizing the Yellow/Blue emission intensity ratios, white light emission can be realized. Dy3+ (4f9) displays approximately 4 emission peaks at around 480 nm, 575 nm, 670 and 758 nm corresponding to transitions from the metastable 4F9/2 state to various lower states, such as 6H15/2 (blue), 6H13/2 (yellow), 6H11/2 (red) and 6H9/2 (brownish red), respectively. In general, the hypersensitive transition at 6H13/2 (yellow) is electric dipole in nature and becomes prominent only when Dy3+ ions are positioned at low symmetric sites with no inversion symmetry in the host matrix. On the other hand, the blue magnetic dipole transition at 6H15/2 becomes prominent only when Dy3+ ions are positioned at highly symmetric sites in the host material with inversion symmetry. Despite the white colour emission from the Dy3+ ions, these transitions are mainly associated with parity forbidden 4f -4f transitions, the white light produced maybe diminished at times, hence the need to include a sensitizer to bolster the forbidden transitions experienced by Dy3+ ions. In this review we will focus on the variability of the Yellow/Blue emission intensities in different host materials (phosphates, silicates, and aluminates) from Dy3+ ions (doped or undoped) by studying their photoluminescent properties (PL), their CIE chromaticity coordinates and correlated colour temperature (CCT) values for white colour emissions that is adaptable to different environmental conditions.

Structural Investigation and Optical Properties of Dysprosium (Dy3+) Ions Doped Oxyfluoro Antimony Borate Glasses for Photonics Applications.

Dysprosium oxide-doped glasses with a composition of 60B2O3-10Sb2O3-10Al2O3-10NaF-(10-x) LiF-xDy2O3 (x = 0.1,0.5, 1.0,1.5,2.0,2.5 mol%) were prepared using a conventional melt-quenching technique. The glasses were characterized through various analytical investigations, including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, refractive index, density, optical absorption, excitation, photoluminescence (PL) studies, decay measurements and radiation shielding parameters. The XRD and FT-IR confirms the glassy nature and functional groups present in the titled glass. The absorption spectra were used to determine the oscillator strength of the Dy3+ absorption transitions as well as the bond created with the O-2 ion in the titled glass network. The degree of the suitability of developed glasses for lasing applications was demonstrated by radiative parameters determined using Judd-Ofelt theory. In the prepared glass samples, the optical bandgap measurements indicate the presence of non-bridging oxygen (NBOs), localization of charges and donor centers in the titled glasses. Due to the de-excitation of 4F9/2 to the corresponding 6H15/2,6H13/2 and 6H11/2 states, the PL emission spectrum shows two main strong emissions at blue(480nm), yellow (575nm) and one less emission at red (663nm). The CIE coordinates determined using PL emission spectra reveal the coordinates that are falling within the white light region. Various shielding parameters such as mass attenuation coefficient, mean free path, effective atomic number were estimated to understand the radiative shielding nature of the titled glasses. Within the addition of Dy2O3, it was found that the shielding parameters values of the titled glass samples are increasing. The Mass Attenuation Coefficient, Half Value Layer and Mean Free Path of the as prepared glasses has been compared with different types of concretes to understand the shielding effectiveness of prepared glass.

Synthesis and effects of co-dopants (La3+ , Sm3+ , Mn2+ , Nd3+ , V5+ , Y3+ ) on photoluminescence of SrAl2 O4 :Dy3+ phosphor.

In this research, the co-dopant effects on photoluminescence (PL) properties of SrAl2 O4 :Dy3+ phosphors were studied. The phosphor powders were prepared with solid state reaction, which is the method that is frequently preferred in SrAl2 O4 phosphors and efficient results are obtained in terms of PL properties. X-ray diffraction (XRD) patterns of all co-doped samples were fitted with pdf card#01-034-0379. Fourier-transform infrared (FTIR) analysis supports the phase evolution determined in the XRD results. PL examinations started with the SrAl2 O4 that was synthesized with the addition of boron, and then continued with the doped/and co-doped samples. Except for the Sm3+ co-doped phosphor, PL data of characteristic Dy3+ transitions were obtained for other lanthanide and metal ion co-dopants. The strongest PL intensity was demonstrated in the SrAl2 O4 :Dy3+ ,V5+ . SrAl2 O4 :Dy3+ ,Sm3+ phosphor shows both the Dy3+ and Sm3+ ions transition related peaks appeared in the same spectrum. In the continuation of the studies, SrAl2 O4 :Dy3+ ,Sm3+ and SrAl2 O4 :Dy3+ ,V5+ powders were immersed in water for 2 h. Regardless of the presence of Dy3+ luminescent centers and other co-dopants, broadband and intense blue emission peak at 445 nm was recorded which is directly related to newly formed phases by the decomposition of SrAl2 O4 .

Luminous LaAlO3 :Dy3+ perovskite nanomaterials: Synthesis, structural, and luminescence characteristics for white light-emitting diodes.

A single-phase perovskite LaAlO3 :Dy3+ phosphor was synthesized using a gel-combustion method at 600°C utilization with hexamethylenetetramine as a fuel. Further calcination of the samples was carried out (800 and 1000°C) to investigate the resultant effect on the crystalline and luminescence behaviour. The crystal structure had a cubic unit cell (space group Pm3̅m) and was examined using the Rietveld refinement and X-ray diffraction data. Additionally, Debye-Scherrer and Williamson-Hall equations were applied to determine other structural features. The particle size and morphology of phosphors were evaluated using transmission electron microscopy. Diffraction measurements were supported by the various metal-oxygen vibration modes studied with the help of Fourier transform infrared spectroscopy. Energy-dispersive X-ray analysis verified the chemical composition of synthesized sample. Luminescence spectra of the LaAlO3 :Dy3+ phosphors exhibited intense bands for 4 F9/2 →6 H15/2 (482 nm, bluish region) and 4 F9/2 →6 H13/2 (574 nm, yellowish region) transitions. Commission Internationale de L'Eclairage and correlated colour temperature data confirmed the cool-white emission of the samples under ultraviolet light excitation. The interesting and advantageous luminescence characteristics of LaAlO3 :Dy3+ phosphors make them potential materials for white light-emitting diodes.

Colour-switchable and photoluminescent polyvinyl chloride for multifunctional smart applications.

Recycled polyvinyl chloride (PVC) waste was used to prepare transparent materials with long-lasting phosphorescence, photochromic activity, hydrophobicity, strong optical transmission, ultraviolet (UV) light protection, and stiffness. Lanthanide-activated aluminate (LaA) microparticles were prepared using a high temperature solid-state procedure, and were subjected to top-down grinding technology to produce lanthanide-aluminate nanoparticles (LaAN). Laminated PVC bottles were shredded into a transparent plastic matrix, which was combined with LaAN and drop casted to produce smart materials for various applications. Smart windows and photochromic film for smart packaging can be made from recycled PVC waste by immobilizing it with various ratios of LaAN. Long-lasting phosphorescent translucent PVC smart windows and films need LaAN to be evenly dispersed in PVC without clumping. Different analytical methods were used to assess the material's morphological structure and chemical composition. Photoluminescence and decay spectra were all used to investigate the luminescence characteristics. In addition, the mechanical performance was studied. According to Commission Internationale de l'Éclairage laboratory colour measurements, this transparent PVC smart material becomes bright green under UV rays and turns a greenish-yellow in the dark. The PVC luminescence was observed to exhibit apparent emission bands at 429 and 513 nm when excited at 367 nm. Improvements were monitored in UV shielding and hydrophobicity when increasing the phosphor concentration. LaAN-immobilized PVC exhibited reversible photochromism. The present approach can be applied to various applications such as anticounterfeiting films for smart packaging, smart windows, and warning light marks.

Exploiting High-Energy Emissions of YAlO3:Dy3+ for Sensitivity Improvement of Ratiometric Luminescence Thermometry.

The sensitivity of luminescence thermometry is enhanced at high temperatures when using a three-level luminescence intensity ratio approach with Dy3+- activated yttrium aluminum perovskite. This material was synthesized via the Pechini method, and the structure was verified using X-ray diffraction analysis. The average crystallite size was calculated to be around 46 nm. The morphology was examined using scanning electron microscopy, which showed agglomerates composed of densely packed, elongated spherical particles, the majority of which were 80-100 nm in size. The temperature-dependent photoluminescence emission spectra (ex = 353 nm, 300-850 K) included Dy3+ emissions in blue (458 nm), blue (483 nm), and violet (430 nm, T 600 K). Luminescence intensity ratio, the most utilized temperature readout method in luminescent thermometry, was used as the testing method: a) using the intensity ratio of Dy3+ ions and 4I15/2→6H15/2/4F9/2→6H15/2 transitions; and b) employing the third, higher energy 4G11/2 thermalized level, i.e., using the intensity ratio of 4G11/2→6H15/2/4F9/2→6H15/2 transitions, thereby showing the relative sensitivities of 0.41% K-1 and 0.86% K-1 at 600 K, respectively. This more than doubles the increase in sensitivity and therefore demonstrates the method's usability at high temperatures, although the major limitation of the method is the chemical stability of the host material and the temperature at which the temperature quenching commences. Lastly, it must be noted that at 850 K, the emission intensities from the energetically higher levels were still increasing in YAP: Dy3+.

Self-reduction synthesis and luminescence properties of Eu, Dy co-doped SrMg2 (PO4 )2 phosphor.

A series of SrMg2 (PO4 )2 :Eu2+ -Eu3+ ,Dy3+ phosphors was synthesized successfully using a high-temperature solid-state method in an air atmosphere. The structures were studied in detail using X-ray diffraction (XRD) and the luminescence properties of the samples. SrMg2 (PO4 )2 :Eu2+ -Eu3+ samples can emit adjustable blue-violet light by controlling the proportion of dopant concentration of europium and dysprosium under 340 nm excitation. Dy3+ exhibits typical blue and yellow emission under 350 nm excitation. The energy transferred from Eu3+ to Dy3+ in Dy and Eu co-doped system was determined by comparing the fluorescence spectra of single-doped system. In addition, the colour coordinates of the International Commission on lighting (CIE) indicated that SrMg2 (PO4 )2 :Eu2+ -Eu3+ ,Dy3+ could be considered as a potential blue-purple phosphor for white light-emitting diode applications.

Energy transfer analysis and realization of cool to warm white light in Dy3+ /Sm3+ /Er3+ triply doped multicomponent borosilicate glass for white light generation.

A series of Dy3+ /Sm3+ /Er3+ triply doped multicomponent borosilicate glasses (DSE) was synthesized using varying Er3+ ions concentrations through a conventional melt quenching technique. The influence of triple doping on the optical characteristics of the prepared glass was evaluated to estimate the possibility of achieving white light emission through optical absorption, photoluminescence excitation (PLE), and emission (PL) measurements. Based on the PLE and PL spectral profiles, the presence of energy transfer processes between Dy3+ , Sm3+ , and Er3+ was confirmed. Furthermore, for Dy3+ /Sm3+ /Er3+ triply doped glass, an enhancement in Er3+ green luminescence and a noticeable decrease in Dy3+ and Sm3+ emissions were detected with the increase in Er3+ concentration. The nature of energy transfer in DSE glass was investigated through Dexter's energy transfer mechanisms and the obtained result suggested that a dipole-dipole interaction was responsible for the dominant Sm3+ to Dy3+ and Dy3+ to Er3+ energy transfer processes. The precise characteristic colours that emanated from the as-prepared samples were evaluated using Commission Internationale de l'Éclairage co-ordinates and correlated colour temperature values and suggested its suitability for white light emission. The quantum efficiency of the prepared glass was determined experimentally. The aforementioned results recommend that the Dy3+ /Sm3+ /Er3+ triply doped multicomponent borosilicate glass irradiated with ultraviolet light sources might be useful for the generation of cool/warm white light-emitting applications.

Silver Nanoparticles Enhance Thermoluminescence and Photoluminescence Response in Li2B4O7 Glass Doped with Dy3+ and Yb3.

Lithium borate glass matrices doped with Dy3+ and Yb3+, containing silver nanoparticles in different concentrations are synthesized and characterized in this work. The Scanning Transmission Electron Microscopy confirms formation of silver nanoparticles in the samples. Absorption spectra of the samples show the presence of a broadband spectrum associated due to the surface plasmon effect of the silver nanoparticles. A strong surface plasmon band bellow 400 nm appears after the annealing process, due to the formation of silver nanoparticles with radius of 5-15 nm. The transition peaks of Dy3+ are also observed at 386, 446, 798, 917, 1088, 1265 and 1669 nm. Additionally, a large peak at 976 nm belonging to the absorption band corresponding to the Yb3+ is observed. Emission spectra under 406 nm pumping show two prominent bands at 506 and 590 nm belonging to the Dy3+ transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2, respectively. The fluorescence in the 480 nm and 525 nm spectral ranges enhanced with the silver nanoparticles contained in the samples. Is the first time, the luminescence studies of the lithium borate matrix doped with Dy3+ and Yb3+ containing silver nanoparticles is done. The basic parameters defining the lasing-amplifying potential of the glass matrices as a function of silver nanoparticles concentration are calculated. The Thermoluminescence response to UV irradiation also exhibits significant enhancement with the increment of silver nanoparticles in the samples.

Investigation of Spectral Interactions between a SrAl2O4:Eu2+, Dy3+ Phosphor and Nano-Scale TiO2.

Herein, we studied light induced interactions between two well-known luminescent materials, SrAl2O4:Eu2+, Dy3+ and nano-scale TiO2 in poly(methyl methacrylate) (PMMA). These two materials were chosen due to their stable nature, efficient spectral properties and more specifically, overlapping excitation/emission bands. When these materials were used together in 1:1 ratio by weight (w/w), the composite exhibited 76% enhancement in the emission intensity with respect to the individual phosphor. Although the luminescence mechanism of both materials is clarified in the literature, spectral interactions of them have not been studied up to now. In our opinion, the TiO2 nano-particles (TiO2 NPs) act as light-harvesting agents for the phosphor particles creating a substantial enhancement on the light absorption efficiency of the phosphor. Additionally, the TiO2 nanoparticles suggest a promising way to boost the phosphorescent activity of the SrAl2O4:Eu2+, Dy3+ by a cost-effective way and further investigation of the mechanism may be subject of future studies.

Molten salt synthesis and luminescence of Dy3+ -doped Y3 Al5 O12 phosphors.

Dy3+ -doped Y3 Al5 O12 phosphors were prepared at a relatively low temperature using molten salt synthesis. The phase of the prepared Dy3+ -doped Y3 Al5 O12 phosphors was confirmed using X-ray powder diffraction. Results indicated that Dy3+ doping did not change the Y3 Al5 O12 phase. Following excitation at 352 nm, emission spectra of the Dy3+ -doped Y3 Al5 O12 phosphors consisted of blue, yellow, and red emission bands. The influence of Dy3+ concentration and excitation wavelength on emission was investigated. The ratio of yellow light to blue light varied with change in Dy3+ doping concentration, due to changes in the structure around Dy3+ . Emission intensities also changed when the excitation wavelength was changed. This variation is luminescence generated a system for tunable white light for Dy3+ -doped Y3 Al5 O12 phosphors.

Yellow Emission Obtained by Combination of Broadband Emission and Multi-Peak Emission in Garnet Structure Na2YMg2V3O12: Dy3+ Phosphor.

The fabrication and luminescent performance of novel phosphors Na2YMg2V3O12:Dy3+ were investigated by a conventional solid-state reaction method. Under near-UV light, the Na2YMg2V3O12 host self-activated and released a broad emission band (400-700 nm, with a peak at 524 nm) ascribable to charge transfer in the (VO4)3- groups. Meanwhile, the Na2YMg2V3O12:Dy3+ phosphors emitted bright yellow light within both the broad emission band of the (VO4)3- groups and the sharp peaks of the Dy3+ ions at 490, 582, and 663 nm at a quenching concentration of 0.03 mol. The emission of the as-prepared Na2YMg2V3O12:Dy3+ phosphors remained stable at high temperatures. The obtained phosphors, commercial Y2O3:Eu3+ red phosphors, and BaMgAl10O17:Eu2+ blue phosphors were packed into a white light-emitting diode (WLED) device with a near-UV chip. The designed WLED emitted bright white light with good chromaticity coordinates (0.331, 0.361), satisfactory color rendering index (80.2), and proper correlation to a color temperature (7364 K). These results indicate the potential utility of Na2YMg2V3O12:Dy3+ phosphor as a yellow-emitting phosphor in solid-state illumination.

Study of luminescence properties of dysprosium-doped CaAl12 O19 phosphor for white light-emitting diodes.

Dy3+ -doped CaAl12 O19 phosphors were synthesized utilizing a combustion method. Crystal structure and morphological examinations were performed respectively using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques to identify the phase and morphology of the synthesized samples. Fourier transform infrared spectroscopy (FTIR) estimations were carried out using the KBr method. Photoluminescence properties (excitation and emission) were recorded at room temperature. CaAl12 O19 :Dy3+ phosphor showed two emission peaks respectively under a 350-nm excitation wavelength, centered at 477 nm and 573 nm. Dipole-dipole interaction via nonradiative energy shifting has been considered as the major cause of concentration quenching when Dy3+ concentration was more than 3 mol%. The CIE chromaticity coordinates positioned at (0.3185, 0.3580) for the CaAl12 O19 :0.03Dy3+ phosphor had a correlated color temperature (CCT) of 6057 K, which is situated in the cool white area. Existing results point out that the CaAl12 O19 :0.03Dy3+ phosphor could be a favorable candidate for use in white light-emitting diodes (WLEDs).

Enhanced photoluminescence properties of electrospun Dy3+ -doped ZnO nanofibres for white lighting devices.

Dy3+ -doped ZnO nanofibres with diameters from 200 to 500 nm were made using an electrospinning technique. The as-fabricated amorphous nanofibres resulted in good crystalline continuous nanofibres through calcination. Dy3+ -doped ZnO nanofibres were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), ultraviolet-visible (UV-vis) light spectroscopy, Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL). XRD showed the well defined peaks of ZnO. UV-vis spectra showed a good absorption band at 360 nm. FTIR spectra showed a Zn-O stretching vibration confirming the presence of ZnO. Photoluminescence spectra of Dy3+ -doped ZnO nanofibres showed an emission peak in the visible region that was free from any ZnO defect emission. Emissions at 480 nm and 575 nm in the Dy3+ -doped ZnO nanofibres were the characteristic peaks of dopant Dy3+ and implied efficient energy transfer from host to dopant. Luminescence intensity was found to be increased with increasing doping concentration and reduction in nanofibre diameter. Colour coordinates were calculated from photometric characterizations, which resembled the properties for warm white lighting devices.

White Light Emitting MZr4(PO4)6:Dy3+ (M = Ca, Sr, Ba) Phosphors for WLEDs.

A series of MZr4(PO4)6:Dy3+ (M = Ca, Sr, Ba) phosphors were prepared by the solid state diffusion method. Confirmation of the phase formation and morphological studies were performed by X-ray powder diffraction (XRD) measurements and scanning electron microscopy, respectively. Photoluminescence (PL) properties of these phosphors were thoroughly analyzed and the characteristic emissions of Dy3+ ions were found to arise from them at an excitation wavelength of 351 nm. The PL emission spectra of the three phosphors were analyzed and compared. The CIE chromaticity coordinates assured that the phosphors produced cool white-light emission and hence, they are potential candidates for UV excited white-LEDs (WLEDs). Graphical Abstract ᅟ.

Synthesis and Luminescence Characterization of LaBO3:Dy3+ Phosphor for Stress Sensing Application.

LaBO3:xDy3+ (x = 0.05 mol%, 0.1 mol%, 0.2 mol%, 0.5 mol%, 1 mol% and 2 mol%) phosphors were synthesized by solid-state reaction method. X-ray diffraction technique was used to confirm the formation of compound. Photoluminescence emission spectra shows two emission peaks at 470 nm and 575 nm when excitation wavelength is set at 352 nm. Photoluminescence intensity increases upto 1 mol % of Dy3+ and then starts decreasing. Dipole-dipole interaction is found to be responsible for concentration quenching of photoluminescence intensity. Commission Internationale de I'Eclairage (CIE) chromaticity diagram demonstrates that the phosphor emits in bluish white region of the visible spectrum. Critical energy transfer distance between dopant ions was determined. The mechanoluminescence characteristics were studied by the impact method. The peaks of both the mechanoluminescence (ML) intensity and the total ML intensity of the UV exposed phosphors increases with increasing impact velocity for 1 mol % concentration of Dy3+. The ML sensitivity of the LaBO3:Dy3+ (Dy3+ = 1 mol %) phosphor is comparable with the reported ML of various inorganic phosphors. The thermoluminescence characteristics of the samples were also investigated. Thermoluminescence glow peaks were recorded with 480 Gy, 80 Gy and 20 Gy dose of γ-irradiation from Co60 Source. TL trapping parameters were determined by Chen's peak shape method and glow curve deconvolution method. LaBO3:Dy3+ phosphors were found to be good mechanoluminescent materials and can be used in stress sensing application.

Gd2O3:RE³âº and GdAlO3:RE³âº (RE = Eu, Dy) Phosphor: Synthesis, Characterization and Bioimaging Application.

Citrate based sol­gel method is used to synthesize Gd2O3:RE³âº and GdAlO3:RE³âº (RE = Eu, Dy) phosphors. In the present work, the phosphors are characterized using the techniques like X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). Fluorescence confocal microscopy reveals the potential usage of phosphors in biological medium for biolabeling application. XRD patterns confirm the phase purity of Gd2O3 and GdAlO3. The crystallite size and lattice parameters are estimated from XRD result. FTIR spectra are used to investigate the functional group present in the phosphor. The optical emission properties imply that the emission peak positions on Eu³âº or Dy³âº ion are size and host independent. Finally, RAW 264.7 macrophages cell line is used to test the bioimaging performance of the phosphors.

White- and blue-light-emitting dysprosium(III) and terbium(III)-doped gadolinium titanate phosphors.

Here we report the synthesis and structural, morphological, and photoluminescence analysis of white- and blue-light-emitting Dy3+ - and Tm3+ -doped Gd2 Ti2 O7 nanophosphors. Single-phase cubic Gd2 Ti2 O7 nanopowders consist of compact, dense aggregates of nanoparticles with an average size of ~25 nm for Dy3+ -doped and ~50 nm for Tm3+ -doped samples. The photoluminescence results indicated that ultraviolet (UV) light excitation of the Dy3+ -doped sample resulted in direct generation of white light, while a dominant yellow emission was obtained under blue-light excitation. Intense blue light was obtained for Tm3+ -doped Gd2 Ti2 O7 under UV excitation suggesting that this material could be used as a blue phosphor.

Concentration dependence of luminescence efficiency of Dy3+ ions in strontium zinc phosphate glasses mixed with Pb3 O4.

In this work we synthesized SrO-ZnO-P2 O5 glasses mixed with Pb3 O4 (heavy metal oxide) and doped with different amounts of Dy2 O3 (0.1 to 1.0 mol%). Subsequently their emission and decay characteristics were investigated as a function of Dy2 O3 concentration. The emission spectra exhibited three principal emission bands in the visible region corresponding to 4 F9/2  â†’ 6 H15/2 (482 nm), 6 H13/2 (574 nm) and 6 H11/2 (663 nm) transitions. With increase in the concentration of Dy2 O3 (upto 0.8 mol%) a considerable increase in the intensity of these bands was observed and, for further increase, quenching of photoluminescence (PL) output was observed. Using emission spectra, various radiative parameters were evaluated and all these parameters were found to increase with increase in Dy2 O3 concentration. The Y/B integral emission intensity ratio of Dy3+ ions evaluated from these spectra exhibited a decreasing trend with increase in the Dy2 O3 concentration up to 0.8 mol%. Quenching of luminescence observed in the case of the glasses doped with 1.0 mol% is attributed to clustering of Dy3+ ions. The quantitative analysis of these results together with infra-red (IR) spectral studies indicated that 0.8 mol% is the optimum concentration of Dy3+ ions needed to achieve maximum luminescence efficiency. Copyright © 2016 John Wiley & Sons, Ltd.

PL Properties of Sr2CeO4 With Eu(3+) and Dy(3+) for Solid State Lighting Prepared by Precipitation Method.

Photoluminescence studies of pure and Dy(3+), Eu(3+) doped Sr2CeO4 compounds are presented by oxalate precipitation method for solid state lighting. The prepared samples also characterized by XRD, SEM (EDS) and FTIR spectroscopy. The pure Sr2CeO4 compound displays a broad band in its emission spectrum when excited with 280 nm wavelength, which peaks centered at 488 nm, which is due to the energy transfer between the molecular orbital of the ligand and charge transfer state of the Ce(4+) ions. Emission spectra of Sr2CeO4 with different concentration of Dy(3+) ions under near UV radiation excitation, shows that intensity of luminescence spectra is found to be affected by Dy(3+) ions, and it increases with adding some percentages of Dy(3+) ions. The maximum doping concentration for quenching is found to be Dy(3+) = 0.2 mol % to Sr(2+)ions. The observed broad spectrum from 400 to 560 nm is mainly due to CT transitions in Sr2CeO4 matrix and some fractional contribution of transitions between (4)F9/2 → (6)H15/2 of Dy(3+) ions. Secondly the effect of Eu(3+) doping at the Sr(2+) site in Sr2CeO4, have been studied. The results obtained by doping Eu(3+) concentrations (0.2 mol% to 1.5 mol%), the observed excitation and emission spectra reveal excellent energy transfer between Ce(4+) and Eu(3+). The phenomena of concentration quenching are explained on the basis of electron phonon coupling and multipolar interaction. This energy transfer generates white light with a color tuning from blue to red, the tuning being dependent on the Eu(3+) concentration. The results establish that the compound Sr2CeO4 with Eu(3+) = 1 mol% is an efficient "single host lattice" for the generation of white lights under near UV-LED and blue LED irradiation. The commission internationale de I'Eclairage (CIE) coordinates were calculated by Spectrophotometric method using the spectral energy distribution of prepared phosphors.