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 paper reports on the thermoluminescence (TL) properties of Eu doped in two different host matrix phosphors (YO and YBO). The phosphors were prepared by a high temperature solid state reaction method. The method is suitable for a large scale production. The samples were characterized by X-ray diffraction and Rietveld refinement. The different concentration of Eu samples were also examined by TL glow curve analysis for UV, β and γ irradiation. The YO samples showed well resolved broad peaks that covered the temperature range from 50 to 350 °C and the peak temperature was found at 157 °C for the γ irradiation. For the UV irradiated samples a well resolved peak at 121 °C was found for the YO:Eu doped phosphors. The β irradiated samples showed a resolved peak at 182 °C. A different behaviour was observed for the YBO:Eu doped phosphors which showed both higher temperature peaks and lower temperature peaks for UV, β and γ irradiation. Here UV irradiated sample showed the formation of shallow trap (surface trapping) and the γ irradiated sample showed the formation of deep trapping. The estimation of the trap formation was evaluated by the calculation of the trapping parameters. The trapping parameters such as activation energy, order of kinetics and frequency factor were calculated by the peak shape method using the computerized glow curve deconvolution technique. Here most of the peak showed second order of kinetics. The effect of γ, β and UV dose exposure on the TL studies was also examined and it showed a linear response with dose which indicated that the samples might be useful for TL dosimetry. The possible mechanics and information about traps formation are presented in detail. [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]

Luminescence behaviour was displayed by dysprosium (Dy) doped BaTiO phosphor which was synthesized via solid state reaction method. The method is suitable for large scale production and useful for production of micron size phosphor. The sample was characterized by X-ray diffraction technique and crystallite size was calculated using Scherer's formula. Effects of optimized concentration of Dy on its thermoluminescence glow curve analysis were carried out for γ irradiation. For fixed concentration of dysprosium ions the TL glow curve was recorded using 6.7 °C s heating rate. Also for variable γ dose 1-2.5 kGy and optimized concentration of dysprosium ion i.e. 4 mol% were carried out. It is found that TL glow curve shows linear response with γ dose. Kinetic parameters were calculated using computerized glow curve deconvolution technique. Photoluminescence study of Dy doped BaTiO phosphor was carried out and it is found that the PL emission spectra in visible region had blue, green and red emission wavelength. CIE coordinate shows color rendering index and correlated color temperature for white light emission of Dy doped BaTiO phosphor. It may be used for visible light emission in display device applications and TL dosimetric applications. [ABSTRACT FROM AUTHOR]

The NaYF 4 phosphors codoped with Er 3+ -Yb 3+ have been synthesized by hydrothermal method using oleic acid as a chelating agent. The crystal structure and surface morphology has been identified with the help of powder X-ray diffraction (PXRD) and field emission scanning microscopy (FE-SEM) technique, respectively. The presence of different functional groups in the developed phosphors have been analyzed by using the Fourier transform infrared spectroscopy (FTIR) technique. The optical non-linear behavior of the prepared phosphors has been performed by using the excitation at 980 nm from a CW diode laser. The effect of Li + ions tri-doping on the structural and luminescence behavior of the Er 3+ -Yb 3+ codoped NaYF 4 phosphors has been discussed suitably. The effect of variation of pump power density on the UC emission intensity of different bands has been investigated. The optical temperature sensing behavior based on the green UC emissions of the Er 3+ -Yb 3+ -Li + tri-doped NaYF 4 phosphors under the excitation at very low pump power density (∼0.32 W/cm 2 ) has been studied. The results obtained from the present study indicate that the Er 3+ -Yb 3+ -Li + tri-doped NaYF 4 phosphors may be of particular interest in developing the NIR to visible upconverters, green display devices and temperature sensors. [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]

In this paper we review the luminescence properties of Pr-doped CaTiO phosphors, the different methods of sample preparation, and characterization of the materials by use of different techniques, for example X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermo-gravimetric analysis, and atomic force microscopy. Solid-state, sol-gel (SG), and combustion methods are most often used for preparation. The high calcining temperature of the solid-state method can be reduced by addition of rare earth oxides (lanthanide series) LnO and LuO. By use of tetra- n-butyl titanates and calcium nitrates as raw material in the modified solid-state method the luminous properties of samples can be optimized at lower sintering temperatures (600 °C) in less time. SG procedures lead to substantial reinforcement of red photoluminescence intensity so can be regarded as the best technique for phosphor preparation. [ABSTRACT FROM AUTHOR]

The present paper reports the thermoluminescence (TL) glow curve of Eu-activated SrAlO phosphor with different UV exposure times. Evaluation of kinetic parameters was done by the peak shape method. The recorded glow curve shifts towards lower temperatures with respect to increasing UV exposure time. The peaks were found at 146.76, 141.34 and 140.37 °C, respectively, for 5, 10 and 15 min of UV exposure using the heating rate of 3°C s. The glow peak shows the second-order kinetics. Different kinetic parameters, i.e. trap depth, order of kinetics, activation energy, and frequency factor are also calculated. The XRD pattern of the sample is compared with reported XRD using the software match. [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]

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]