Search

The synthesis and luminescence analysis of Tb3+-activated phosphors were reported. Y2SiO5 phosphors were synthesized by a modified solid-state reaction method with a variable doping concentration of Tb3+ ion (0.5–2.5 mol.%). As synthesized, the phosphors were characterized by X-ray diffraction (XRD) analysis. The XRD pattern confirmed the monoclinic structure of the prepared phosphor. Scanning electron microscopy and High-Resolution Transmission Electron Microscopy (HRTEM) studies revealed nearly uniform particle size distribution in the prepared phosphors. The photoluminescence excitation spectra of the Y2SiO5:Tb3+ (0.5–2.5 mol.%) phosphor displayed one broad, intense peak at 258–277 nm. When excited at the 258 nm wavelength, the phosphors showed emission peaks at 553 nm (5D4 → 7F5), 544 nm (5D4 → 7F5) and 489 nm (5D4 → 7F6). The 1931 CIE (x,y) chromaticity coordinates showed the distribution of the spectral region calculated from the photoluminescence emission spectra. The values of x = 0.25 and y = 0.46 were very close to light green emission. Therefore, the prepared phosphor is very useful for light-emitting diode (green component) applications. [ABSTRACT FROM AUTHOR]

Y2Sr3B4O12 phosphors doped with europium ions were synthesized by a modified conventional solid-state reaction method. Characterizations of the prepared samples, viz., X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and Commission Internationale de I'Eclairage were studied. The XRD analysis confirmed the formation of mixed phase due to polyborate and has a hexagonal crystalline yttrium orthoborate phosphor. SEM images showed the irregular morphology of the sample. The grain size distribution was broad and the average size was found to range from 2 μm to 100 nm. PL measurements showed excitation and emission characteristics of the prepared phosphor with different concentrations of the doping ion. From the emission spectra, it was clearly observed that the emission intensity of the magnetic dipole was higher than that of electric dipole transition owing to the Eu3+ ions occupying a higher symmetry site in the Y2Sr3B4O12 host. The intensity of PL increased with increasing concentration of the doping ion up to 2.0 mol.%; after that, the PL intensity decreased owing to the concentration-quenching phenomenon. The results indicated that Y2Sr3B4O12:Eu3+ phosphors can be selected as a potential candidate for solar cell/photovoltaic application. [ABSTRACT FROM AUTHOR]

This Letter presents the electrodeposition of zinc oxide (ZnO) nanostructures by varying the negative potential and investigation of structural, optical, and morphological characteristics. UV–vis spectroscopy investigation showed the redshift of the absorption peak with the increased negative potential. Using Tauc relation, the optical bandgap values estimated to be 3.09, 2.97, 2.93, 2.91, 2.90, and 2.84 eV corresponding to the samples prepared at potential −0.5, −0.7, −0.9, −1.1, −1.3 and −1.5 V. Fluorescence spectra exhibited the UV emission band at wavelength 392 nm along with a peak at 650 nm corresponds to the second‐order nature of ZnO. Fourier‐transform infrared spectroscopy analysis confirmed the various vibration modes at 403, 493, and 702 cm−1 originated by the ZnO nanostructures. X‐ray diffraction pattern revealed the hexagonal wurtzite phase of ZnO. Scanning electron microscopy investigation evidenced the distinct morphology of ZnO with the increased negative potential; however, the dense and perpendicularly oriented ZnO nanorods are prepared at highest negative potential as compared to rice grain‐like ZnO structure prepared at least negative potential. Furthermore, the prepared nanostructures are used as dye‐sensitised solar cells (DSSCs) photoanodes, while the DSSC‐Z6 showed the increased cell efficiency up to 1.2%, due to the aligned growth of the ZnO nanorods. [ABSTRACT FROM AUTHOR]

This review includes research papers on different method of preparation of rare earth activated Sr2SiO4 phosphors and its luminescence studies. Here in Sr2SiO4 has attracted great interest due to its special structure features, excellent physical and chemical stability. Besides, it absorbs ultraviolet radiation and emits white light when activated by different rare earth ions. Different synthesis techniques were compared and it is found that sol–gel synthesis technique is best for preparation of rare earth activated Sr2SiO4 phosphors. Literature related to characterization techniques such as X-ray diffraction techniques, scanning electron microscopy, transmission electron microscopy and other studies are also compared. Photoluminescence studies for white light emitting diode of various rare earth phosphors are compared with Sr2SiO4 phosphor reported in this review. Also some luminescence techniques such as thermoluminescence glow curve analysis and some spectroscopic parameters are also compared. The review end with some important conclusion related to rare earth activated Sr2SiO4 phosphors with proper justifications. [ABSTRACT FROM AUTHOR]

• Transition metal doped CeO 2 Nps synthesized by co-precipitation method. • Rietveld refinements of high-quality powder XRD show good convergences. • Band gap tunability was seen with transition metal doping in CeO 2 Nps. • Transition metal doping influenced the photoluminescence and optical properties. In this study, pure and transition metal doped (TM = Fe, Co, and Ni), cerium oxide nanoparticles have been synthesized by the co-precipitation techniques. Rietveld refined X-ray diffraction (XRD) patterns affirm the monophase nature with cubic symmetry having an Fm3m space group and crystalline size varies in the range of 9–14 nm calculated by Debye Sherer's formulation. The morphological study has been done by scanning electron microscope (SEM) technique anticipated that agglomerated grains symmetry with the typical grain size distribution varies from 45 to 52 nm. The effect of transition metal doping on bending/stretching vibrational modes has been effectively investigated by FTIR analysis. The strong absorbance edge was seen in the UV region and shifted in the red region with the doping of transition metal ions. The tauc's plot of UV–vis absorption uncovers the bandgap decreased from 2.87 eV to 2.42 eV on transition metal doping. The photoluminescence spectroscopy (PL) technique was used to investigate the presence of oxygen vacancies and intrinsic defects in the host CeO 2 lattice when doped with transition metal ions. These imperfections induce the lattice disorder and shift in the energy bandgap from the UV to the visible region of the spectrum by affecting its electronic transitions. The CIE chromaticity coordinates of pure and transition metal doped compounds observed in the blue region might be applicable in display devices. In this manner, these materials can be fascinating for tuneable electrical and optical devices. [ABSTRACT FROM AUTHOR]

SrAl2O4Eu2+ green-light emitting powder phosphor was prepared within a few minutes at furnace temperature as low as 550 °C by using combustion method. The prepared powder was characterized by X-ray diffraction, scanning electron microscopy and Fourier-transform infrared spectrometry. Several ESR lines are exhibited by the phosphor, and some are seen in the low field region apart from lines in the g ~ 2.0 region. Crystal fields that were relatively strong arose from distortions close to the Eu2+ ion lead to lines in the low field region. The photoluminescence of Eu2+-activated SrAl2O4 shows a green-emission dominant peak around 514 nm, which can be attributed to the 4f65d1 → 4f7 transition of Eu2+ ions from the synthesized phosphor particles at an excitation wavelength of 345 nm. [ABSTRACT FROM AUTHOR]

CeO:M (Eu, Er and Dy) phosphors were synthesized by modified solid-state reaction technique at variable concentrations of Eu, Er and Dy. This technique is suitable for large-scale production and it is less time-consuming. The prepared samples were characterized by X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), and Photoluminescence (PL) decay curve analysis. XRD patterns of the prepared samples confirm the cubic fluorite crystal structure of all phosphors. Crystallite size was calculated by using well known Scherer's formula. SEM images express good surface morphology with nanoflower like shape. Comparative studies of photoluminescence decay curves of CeO:M (Eu, Er and Dy) with different concentrations of dopant have been done. Decay constants for all prepared phosphors were calculated by curve fitting technique. Samples were excited under UV radiation for few nanoseconds at room temperature. The PL decay curves were measured for D→F transition of CeO:Eu,S→I transition of CeO:Er and F→H transition of CeO:Dy phosphors. Decay curve for CeO:Eu (1.5 mol%) phosphor shows optimum concentration with higher intensity of photoluminescence signals and comparatively higher decay constants. [ABSTRACT FROM AUTHOR]

Behavior is displayed by samarium-doped LaAlO3 phosphor which was synthesized by solid state reaction method. For the synthesis of LaAlO3 with variable concentration of Sm (0.2–2.5 mol%) phosphor was calcinated at 1000 °C and sintered at 1250 °C following intermediate grinding. Synthesized sample was characterized by X-ray diffraction analysis and crystallite size was calculated by Scherer's formula. From photoluminescence (PL) spectra of prepared phosphors show broad excitation peak at 250 nm and emission at 566, 600, and 608 nm is obtained. The phosphor is prepared by high temperature synthesis method. Two peaks are obtained in the thermoluminescence (TL) glow curve for lower concentration of Samarium. Single prominent peak is obtained with further increase in the concentration of dopant. It is characteristic yellow-orange emission for samarium ion. The excitation spectra of LaAlO3:Sm3+ phosphor mainly consists of the charge transfer band (CTB) of Sm3+ located in 220–340 nm centered at 250 nm. The present phosphors can act as single host for yellow-orange-red light emission in display devices. The CIE coordinates were calculated by spectrophotometric method using the spectral energy distribution of the LaAlO3 :Sm3+ sample. TL glow curve was recorded for variable concentration of dopant with fixed UV exposer time (20 min) and fixed heating rate (5 °C·s−1). TL glow curve shows broad peak and kinetic parameters are calculated by computerized glow curve deconvolution technique. It is suggested that from TL glow curve analysis prepared phosphor may be useful for TL dosimetric application for UV exposure. [ABSTRACT FROM PUBLISHER]

Near UV-blue emission from cerium ion percentage of ZrO2 phosphor was reported in the manuscript. The samples were prepared by combustion synthesis technique which is suitable for less time taking techniques. Starting material for sample preparation are Zr(NO3)3 and Ce(NO3)3 and urea used as a fuel. Here the variable percentage of cerium ion was (0.1 to 2.5 mol%) used. The prepared sample was characterized by X-ray diffraction analysis for structural analysis and it is found the cubic structure also crystallite size were calculated by Scherer's formula. Morphology and particle size of prepared sample for optimized concentration of cerium was analyzed by field emission gun scanning electron microscopy and high resolution transmission electron microscopy technique. All prepared phosphor with variable concentration of Ce3+ (0.1 to 2.5 mol%) was studied by photoluminescence analysis and it is found that the excitation spectra of prepared phosphor shows broad excitation centred at 396 nm (near UV-blue region). The emission spectra with variable concentration of Ce3+ show strong peaks at 447 nm (blue region). Spectrophotometric determinations of peaks are evaluated by Commission Internationale de I’Eclairage (CIE) technique. Using this phosphor, the desired CIE values including emissions throughout the violet (396 nm) and intense blue (427 nm) of the spectra were achieved. Efficient blue light emitting diodes (LEDs) were fabricated using Ce 3+ doped phosphor based on near ultraviolet excited LED lights. Also the prepared phosphor was useful for sensing application such as biological and chemical sensing. [ABSTRACT FROM PUBLISHER]

The behavior displayed by photoluminescence and thermoluminescence of BaTiO{3} phosphor activated by samarium ion reported in the manuscript. Sample was prepared by solid state reaction method with calcination temperature 600 ^\circC and sintered at 950 ^\circC. The prepared sample was characterized by X-ray diffraction analysis and matched with COD card number using Celref V3 software. Samarium concentration was fixed i.e., 1 and 1.5 mol% for synthesis. Photoluminescence excitation and emission spectra were recorded and intense peak found at yellow region which shows the transition of samarium ion. Spectrophotometric determination was recorded by CIE technique and it shows the color rendering index of prepared phosphor. For Thermoluminescence glow curve analysis sample was irradiated by gamma dose 0.5–2 kGy using Co^60gamma source. It shows intense broad TL glow curve at 185 ^\circC with a high temperature shoulder peak at 221 ^\circC. It shows a greater number of traps generated in the prepared sample. The associated peak in the broad TL glow curve was separated by the CGCD technique. Kinetic parameters are calculated by the peak shape method using the CGCD technique. [ABSTRACT FROM PUBLISHER]

CeO{2}:Dy^3+ phosphors were synthesized by modified conventional solid-state reaction method. The formation of a CeO{2} structure is confirmed via XRD studies. The luminescence measurement upon excitation in ultraviolet and visible range shows the characteristics Dy^3+ excitation and emission. The occurrence of charge transfer band is explained in detail. The emission spectrum of Dy ions consists mainly of several groups of lines in the 450–625-nm region, due to the transitions from the ^4F{9/2}-{6}H{15/2} (blue emission) and the ^4F{9/2}-{6}H{13/2} (yellow emission) of Dy ions. The phenomena of concentration quenching are explained on the basis of electron phonon coupling and multipolar interaction. Different spectral parameters are calculated via the Judd Ofelt approach. The purity of the white light emission is also examined, and it makes Dy^3+ doped CeO{2} a promising candidate for applications in displays and optical device. [ABSTRACT FROM PUBLISHER]

The present paper reports the synthesis, photoluminescence (PL), and thermoluminescence (TL) studies of Eu-doped yttrium oxide (YO) phosphor using inorganic materials like YO, flux calcium fluoride, and europium oxide. The sample was prepared by the modified solid state reaction method, which is the most suitable for large-scale production. The prepared phosphor sample was characterized using powder X-ray diffraction, field emission gun scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy , PL, TL, and Commission Internationale de I'Eclairage techniques. The PL emission was observed in the range 417-632 nm ranges all visible regions for the YO phosphor doped with Eu. Excitation spectrum found at 254 nm. Sharp intense peaks found around 467, 534, 594, 612, and 632 nm with high intensity. From the XRD data, using the Scherer's formula, the calculated average crystallite size of Eu-doped YO phosphor is around 45 nm. TL study was carried out for the phosphor with UV irradiation. The present phosphor can act as single host for white light emission in display devices. [ABSTRACT FROM AUTHOR]

This paper reports the preparation of Eu 3+ doped Gadolinium oxyorthosilicate (Gd 2 SiO 5 :Eu 3+ ) phosphor with different concentration of Eu 3+ (0.1–2.5 mol%) using the modified solid state reaction method. The synthesis procedure of the Gd 2 SiO 5 :Eu 3+ phosphor using inorganic materials such as Gd 2 O 3 , silicon dioxide (SiO 2 ), europium oxide (Eu 2 O 3 ) and boric acid (H 3 BO 3 ) as flux is discussed in detail. The prepared phosphor samples were characterized by using X-Ray Diffraction (XRD), Field Emission Gun Scanning Electron Microscopy (FEGSEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Photoluminescence (PL) and Thermoluminescence (TL). The Commission Internationale de l′Eclairage(CIE) coordinates were also calculated. The PL emission was observed in the 350–630 nm range for the Gd 2 SiO 5 :Eu 3+ phosphor. PL excitation peaks were observed at 266, 275, 312 and 395 nm while the emission peaks were observed at 380, 416, 437, 545, 579, 589, 607, 615 and 628 nm. The emission peak at 615 nm was the most intense peak for all the different Eu 3+ concentration samples. From the XRD data, using the Scherrer's formula, the average crystallite size of the Gd 2 SiO 5 :Eu 3+ phosphor was calculated to be 33 nm. TL was carried out for the phosphor after both UV and gamma irradiation. The TL response of the Gd 2 SiO 5 :Eu 3+ phosphor for the two different radiations was compared and studied in detail. It was found that the present phosphor can acts as a single host for red emission (1.5 mol%) for display devices and light emitting diode (LED) and white light emission for Eu 3+ (0.1 mol%) and it might be used as a TL dosimetric material for gamma dose detection. [ABSTRACT FROM AUTHOR]

The phosphor of BaZrO 3 doped with different concentration of Eu 3+ ions (0.1, 0.5, 1 mol%) was prepared by solid–state reaction method. The prepared samples were characterized by X-ray diffraction (XRD), photoluminescence (PL) and thermoluminescence (TL) techniques. Analysis of XRD data shows the formation of perovskite structure of prepared phosphor. The room temperature excitation spectra vary with the Eu 3+ concentration and consist of an intense charge transfer band and weak f–f transitions. The PL emission spectra, excited at 254 nm, consist of 4f–4f emission transitions from the 5 D 0 excited level of the Eu 3+ ions to the 7 F J (J = 0–3) levels. The dependence of luminescence intensity on the Eu 3+ concentration in BaZrO 3 :Eu 3+ was studied. The present phosphor can act as single host for intense red emission for display devices application. Commission internationale de I'Eclairage techniques gives information about correlated color temperature and prominent emissions in PL emission spectra. Detail process and possible mechanism for PL and TL are studied and discussed in this paper. For the variable concentration of Eu 3+ ions on PL studies shows the PL intensity increase with increasing the concentration of dopant. In TL glow curve the optimized concentration in 1 mol% for UV irradiated sample. The kinetic parameters were calculated by computerized glow curve deconvolution (CGCD) technique. [ABSTRACT FROM AUTHOR]

A series of Tb3+-doped Li2CaSiO4 phosphors were prepared by high-temperature solid-state reaction method. The structural studies were done using the X-ray diffraction (XRD) technique. The XRD patterns revealed that the sample was monophased and crystallizes in a cubic structure. Scanning electron microscopy (SEM) was used to obtain information about the morphology of the prepared samples. SEM micrographs clearly indicated that the particles crystallized in inhomogeneous morphology, with the particle size ranging from 1 μm to 100 nm. Also, photoluminescence (PL) analysis of the phosphor samples for different concentrations of doping ions with variable excitations were presented. The PL excitation spectrum of Tb3+ ion-doped Li2CaSiO4 has many sharp peaks, mainly at 418 nm (5D3 → 7F5), 436 nm (5D3 → 7F4), 456 nm (5D3 → 7F3), 472 nm (5D3 → 7F2,1,0), 487 nm (5D4 → 7F6), 550 nm (5D4 → 7F5), and 590 nm (5D4 → 7F4), assigned to the transitions of Tb- ion respectively (excited at 237 nm). The 1931 CIE (x, y) chromaticity coordinates showed the distribution of the spectral region calculated from PL emission spectra, and found to be (0.19, 0.22) in a bluish-green region of Tb3+ (0.01 wt (in grams)) Li2CaSiO4 phosphor. Our study shows that as-prepared phosphor may be useful for optical devices, mainly for LEDs, as a bluish-green component. [ABSTRACT FROM AUTHOR]

Abstract: Defect-assisted luminescence of Pr3+-doped SrS has been investigated and reported in this paper. The polycrystalline sample of phosphor was prepared by conventional solid-state reaction method and checked for crystallization and phase by X-ray diffraction study. The thermally stimulated luminescence studies of the phosphor samples with various activator concentrations, irradiated by a blacklight source, are conducted and show a broad single peak around 365–382K. Computerized glow curve deconvolution tool is used to evaluate the effective trapping parameters and suggests quasi-continuous distribution of traps in the range of 0.5−0.9eV. A critical survey on the application of first-order kinetics in the present phosphor is undertaken. Photoluminescence studies reveal three excitation bands at 287, 314, 355nm and defect-related emission at 517, 494nm for two concentrations of activator atoms in the present phosphor. The 314–355nm broad excitation bands correspond to a charge transfer transition of Pr3+-S2−. [Copyright &y& Elsevier]

Phosphors with the composition La 1-x Gd x Al 11 O 18 (x = 0.01–0.10) were synthesized by combustion at a furnace temperature of 500 °C. The formation of the as-prepared combustion products was confirmed by X-ray diffraction analysis. On excitation with 273 nm, an emission band for the Gd 3+ ion was observed at 314 nm. This band progressively enhanced with increasing Gd 3+ concentration. The phosphor with low concentrations of Gd 3+ ions exhibits prominent ESR lines with g eff  ∼ 1.9, 2.0, 4.7, and 5.9. With high dopant concentrations, the spectrum shows features similar to those of a U-spectrum with dominant lines with g eff  ∼ 2.0, 2.9, 4.6, and 6.1. Low field lines arise from distortions in the immediate environment of the Gd 3+ ion. [ABSTRACT FROM AUTHOR]

A successful preparation of a Tb 3+ -doped LiBaB 9 O 15 phosphors was achieved through the use of a solution-combustion method. The preparation of the powders of the Tb 3+ -doped LiBaB 9 O 15 phosphor was confirmed by X-ray diffraction (XRD) results; furthermore, the size and morphology of these powders were further examined using a scanning electron microscope (SEM). A study of the luminescent proprieties under a UV excitation showed a dominant and strong green luminescent peak at 542 nm that is due to the d–f transition. When monitored at 542 nm, the excitation spectrum exhibited a broad band centered at 230 nm and several weak peaks in the wavelength range of 300–400 nm that are attributed to the f-d transitions and the intra-4f-4f transitions of the Tb 3+ ions, respectively. The addition of the Tb 3+ concentration greatly improved the photoluminescent properties of the present phosphors, and the Commission International de I’Eclairage (CIE) chromaticity coordinates are located in the green region. The present study suggests that the potential applications of the Tb 3+ -doped LiBaB 9 O 15 phosphors might be in the lighting and display fields. [ABSTRACT FROM AUTHOR]

ZnAl 2 O 4 doped with varying concentrations of cerium phosphors were synthesized by combustion synthesis route. Two types of powder samples were examined: as-prepared and annealed at 800 °C in air atmosphere. We investigated the structural, morphological and photoluminescence properties of cerium doped ZnAl 2 O 4 phosphors. Results of scanning electron microscopy, X-ray diffraction, photoluminescence investigations were presented. [ABSTRACT FROM AUTHOR]