MgO:Eu3+ red nanophosphor: Low temperature synthesis and photoluminescence properties (original) (raw)
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Nanomaterials and Nanotechnology
Mg1.5Al2O4.5: x% Eu3+ (0 ≤ x ≤ 2) nanopowders were successfully synthesized via sol–gel method. The X-ray diffraction (XRD) spectrum revealed that the Mg1.5Al2O4.5: x% Eu3+ matches the single phase of face-centred cubic MgAl2O4. The estimated average crystallite sizes calculated using the XRD spectra were found to be in the order of 4 nm. The estimated crystal size was confirmed by the high-resolution transmission electron microscopy. The energy dispersive X-ray spectroscopy confirmed the presence of all expected elementary composition (Mg, Al, O and Eu). The field emission gun scanning electron microscope showed that varying the Eu3+ concentration influence the morphology of the prepared nanophosphor. The photoluminescence results showed that the host emits the violet colour at around 382 nm, which was attributed to the defects within the band gap ( Eg) of host material. The Eu3+-doped samples showed the emission at around 560, 580, 593, 618, 655 and 704 nm which are, respectively,...
Optik, 2019
A series of novel red MGdAlO 4 :Eu 3+ (M = Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+) was synthesizedand investigated. The samples were synthesized via rapid-gel combustion route at a temperature of 600°C and examined over large doping concentration of 0.01 to 0.05 mol. The optimal concentration of activator ion has been found to be 0.03 mols for MGdAlO 4 lattice. Using the excitation wavelength of 393 nm, these phosphors exhibited strong emission in the red region owing to 5 D 0 → 7 F 2 (electric dipole allowed) transition located at 610-615 nm. The effect of reaction temperature on luminescence was also analyzed for these materials. The structural characteristics of phosphors were studied via joint approach of X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Diffraction patterns of prepared phosphor contain sharp peaks in 10°-80°region. The proposed materials have single phase tetragonal structure having I4/mmm space group. The degree of crystallization has been found to increase with temperature. The TEM micrographs exhibited the spherical shape of particles in 15-35 nm size. The FTIR spectra of CaGdAlO 4 showed peaks at 699 and 461 cm −1 analogous to Al-O and Gd-O stretching vibrational modes. Due to excellent luminescent response the Eu 3+ doped MGdAlO 4 can be excellent materials for the growth of effective red phosphor in WLEDs and fluorescent panels.
Research Square (Research Square), 2023
In the present work, trivalent europium (Eu 3+) ion activated Mg 3 (PO 4) red phosphors have been synthesized through solid-state reaction method. X-ray diffraction (XRD) con rmed the successful formation of Mg 3 (PO 4) 2 :Eu 3+ phosphors with monoclinic phase (space group P2 1 /c (14). The photoluminescence (PL) spectroscopy was used to record the excitation and emission spectrum of Eu 3+ activated Mg 3 (PO 4) 2 phosphor. The resulting samples displayed the typical emissions of Eu 3+ ions corresponding to the 5 D 0 → 7 F J transitions when excited at 395 nm. A 0.5 mol% Eu3 + ion doping concentration was found to be ideal. The best concentration of Eu 3+ ions for doping was discovered to be 0.5 mol%. The CIE coordinates of Eu 3+ activated Mg 3 (PO 4) 2 phosphor is calculated, which shows strong red emission. In addition, phosphate group replaced with molybdate, tungstate and sulfate group and found enhancement in emission intensity of prepared phosphors. The outcomes showed that the Eu 3+activated Mg 3 (PO 4) 2 phosphors are excellent red-emitting phosphors for use in white LEDs that are driven by near-ultraviolet light.
Photoluminescence and thermoluminescence studies of Mg2SiO4:Eu3+ nano phosphor
Journal of Alloys and Compounds, 2011
Nanoparticles of Eu 3+ doped Mg 2 SiO 4 are prepared using low temperature solution combustion technique with metal nitrate as precursor and urea as fuel. The synthesized samples are calcined at 800 • C for 3 h. The Powder X-ray diffraction (PXRD) patterns of the sample reveled orthorhombic structure with ␣-phase. The crystallite size using Scherer's formula is found to be in the range 50-60 nm. The effect of Eu 3+ on the luminescence characteristics of Mg 2 SiO 4 is studied and the results are presented here. These phosphors exhibit bright red color upon excitation by 256 nm light and showed the characteristic emission of the Eu 3+ ions. The electronic transition corresponding to 5 D 0 → 7 F 2 of Eu 3+ ions (612 nm) is stronger than the magnetic dipole transition corresponding to 5 D 0 → 7 F 1 of Eu 3+ ions (590 nm). Thermoluminescence (TL) characteristics of ␥-rayed Mg 2 SiO 4 :Eu 3+ phosphors are studied. Two prominent and well-resolved TL glows with peaks at 202 • C and 345 • C besides a shoulder with peak at ∼240 • C are observed. The trapping parameters-activation energy (E), order of kinetics (b) and frequency factor (s) are calculated using glow curve shape method and the results obtained are discussed.
Optik, 2018
A simple solution combustion method was adopted to form a series of MgO nanophosphors doped with different mol% of Dy 3+ ions using urea as a fuel. The powder products were well characterized structurally, morphologically and optically by Powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and diffuse reflectance spectra. The elemental confirmation was done through elemental analysis by energy dispersive X-ray spectroscopy (EDX). The XRD patterns show that the final product is cubic in shape with the crystallite size ranging from 25-44 nm along with strain and dislocation densities also supported by HRTEM analysis. Photoluminescence (PL) studies under identical experimental conditions for the UV excitations, the formation of three prominent emission spectra at 488, 590 and 630 nm has been observed. These spectra show the transitions of 4f→6h energy levels, namely 4 F9/2→ 6 H15/2 (488 nm), 4 F9/2→ 6 H13/2 (590 nm) and 4 F9/2→ 6 H11/2 (630nm). The afterglow decay curve shows the single exponential decay for different MgO:Dy 3+ nanophosphors compositions have been studied in detail.
Kinetically stabilized aliovalent europium-doped magnesium oxide as a UV sensitized phosphor
Doping of size mismatched aliovalent ions is challenging due to the associated elastic and electronic stress making the thermodynamics unfavorable. Despite such features, its utilization may be viable if such systems can be made metastable by suppressing the kinetics of phase segregation. In light of such a possibility, we utilize sol–gel synthesis for preparing a size mismatched trivalent europium doped MgO Mg 1Àx Eu x O:ðx=2ÞV 00 Mg system, which can be potentially used in optical applications. It is found that such a doped system can be metastabilized and the extent of metastability can be correlated with critical temperature (T c) required for phase segregation which decreases with the dopant concentration. For x = 0.005, 0.01, and 0.02, T c is above 1200 1C, 500–800 1C and less than 500 1C, respectively. As the synthesis temperature is 500 1C, these trends in critical temperatures make it impossible to metastabilize europium in MgO with x 4 0.01. Doping is evident from X-ray diffraction data, excitation spectra, high resolution emission spectra, and luminescence lifetimes. A characteristic strong red emission of Eu 3+ has been observed via energy transfer from the MgO matrix to Eu 3+. Density functional theory based simulations suggest stabilization of Eu 3+ in MgO at lower doping concentration through the formation of cation vacancies which is also evident from optical studies. Furthermore, thin films deposited using the e-beam evaporation technique from the Mg 1Àx Eu x O:ðx=2ÞV 00 Mg (x = 0.005) system show UV sensitized emission with CIE coordinates (0.26, 0.21).
The MgAl2O4 spinel doped with Eu2+ ions powder phosphor was prepared at temperature as low as 500 oC using the combustion route. A structural property of the powder was characterized by X-ray diffraction (XRD). This XRD pattern shows the well crystallized cubic phase, Fd-3m space group of MgAl2O4. The estimated average crystalline size is about 36 and 30 nm for MgAl2O4 and Eu doped MgAl2O4 particles respectively. The photoluminescent property of prepared powder was investigated using excitation and emission spectroscopy at room temperatures. Energy levels scheme is proposed for emission from MgAl2O4: Eu2+.
Structural and optical behaviour of pure and iron doped MgO nanophosphors
Nucleation and Atmospheric Aerosols, 2020
Mg1-xO: Fe 3+ (x = 0, 0.1, 0.2, 0.3, 0.4) nanophosphors were prepared via solution combustion synthesis (SCS) technique were characterized using powder X-ray diffraction (XRD), Fourier Transformation Infrared (FTIR) Spectroscopy, Photoluminescence (PL) and Thermoluminescence (TL). XRD analysis confirmed the existence of cubic structure. The average crystalline sizes calculated by using Debye Scherer's formula found to be around ~32-39 nm in these samples. FTIR spectra also confirmed the phase purity of the samples. PL spectral analysis revealed the presence of the surface defects namely oxygen vacancies, F-centers/F +-centers. TL intensity decreases by doping of Fe content in MgO nanophosphors. Even at high gamma doses there is no significant increment in TL intensity of Fe doped MgO whereas in case of MgO pure nanophosphor TL intensity increases with increasing Gamma doses.
Crystal Structure and Luminescent Properties of R 2– x Eu x (MoO 4 ) 3 (R = Gd, Sm) Red Phosphors
Chemistry of Materials, 2014
The R 2 (MoO 4 ) 3 (R = rare earth elements) molybdates doped with Eu 3+ cations are interesting red-emitting materials for display and solid-state lighting applications. The structure and luminescent properties of the R 2−x Eu x (MoO 4 ) 3 (R = Gd, Sm) solid solutions have been investigated as a function of chemical composition and preparation conditions. Monoclinic (α) and orthorhombic (β′) R 2−x Eu x (MoO 4 ) 3 (R = Gd, Sm; 0 ≤ x ≤ 2) modifications were prepared by solid-state reaction, and their structures were investigated using synchrotron powder X-ray diffraction and transmission electron microscopy. The pure orthorhombic β′-phases could be synthesized only by quenching from high temperature to room temperature for Gd 2−x Eu x (MoO 4 ) 3 in the Eu 3+ -rich part (x > 1) and for all Sm 2−x Eu x (MoO 4 ) 3 solid solutions. The transformation from the α-phase to the β′-phase results in a notable increase (∼24%) of the unit cell volume for all R 2−x Eu x (MoO 4 ) 3 (R = Sm, Gd) solid solutions. The luminescent properties of all R 2−x Eu x (MoO 4 ) 3 (R = Gd, Sm; 0 ≤ x ≤ 2) solid solutions were measured, and their optical properties were related to their structural properties. All R 2−x Eu x (MoO 4 ) 3 (R = Gd, Sm; 0 ≤ x ≤ 2) phosphors emit intense red light dominated by the 5 D 0 → 7 F 2 transition at ∼616 nm. However, a change in the multiplet splitting is observed when switching from the monoclinic to the orthorhombic structure, as a consequence of the change in coordination polyhedron of the luminescent ion from RO 8 to RO 7 for the αand β′-modification, respectively. The Gd 2−x Eu x (MoO 4 ) 3 solid solutions are the most efficient emitters in the range of 0 < x < 1.5, but their emission intensity is comparable to or even significantly lower than that of Sm 2−x Eu x (MoO 4 ) 3 for higher Eu 3+ concentrations (1.5 ≤ x ≤ 1.75). Electron energy loss spectroscopy (EELS) measurements revealed the influence of the structure and element content on the number and positions of bands in the ultraviolet−visible−infrared regions of the EELS spectrum.