Trivalent europium doped yttriate nanophosphors were synthesized by rapid facile gel combustion technique. The photoluminescence (PL) properties of these Eu3+ activated MY2O4 (M = Mg, Ca, and Sr) nanophosphors showed red luminescence and exhibited excellent emission properties in their respective regions of color coordinates. Based on the excitation wavelengths multiple emission peaks were obtained. The main peak in the emission spectra was ascribed to 5D0→7F2 transition of Eu3+ ion. The structural and morphological studies were performed by the measurements of X-ray diffraction profiles, scanning electron microscope (SEM) images, and transmission electron microscope (TEM) micrographs. Furthermore, the effects of additional heating on the different host lattices of these phosphors were also studied.
Rare earth doped oxide materials have excellent chemical as well as thermal stability along with outstanding luminescent efficiency and their colour purity; consequently these are used for the various applications of display devices [
The RE3+ doped phosphors originate as suitable materials as these show highly intense emission of light. The selected lattice should be having two or more sites for the integration of RE3+ and these sites are also less distant for assisting fast energy transfer between ions. Hence, the obtained phosphors will be highly intense with long decay times even with low doping concentration of rare earth ion. Hence, above both conditions are suitable with these MRE2O4 (M = Ca, Sr, and Ba; RE = Y, Gd, Lu, Sc, and In) lattices. Consequently, Eu3+ doped MRE2O4 luminescent materials are more significant than Eu3+ doped RE2O3 phosphors. In recent times, MRE2O4 oxide lattices have been searched as potential lattices for the synthesis of rare earth activated phosphors [
Generally, phosphor materials are synthesized by various techniques, that is, solid state reaction [
Here, in our work, we used rapid facile gel combustion method for the synthesis of MY2O4:Eu3+ (M = Mg, Ca, and Sr) nanomaterials. The prepared materials are further characterized by X-ray diffraction profiles (XRD), scanning electron microscope (SEM) images, transmission electron microscope (TEM) micrographs, and photoluminescence (PL) spectra. The prepared phosphors particles are obtained in the nanorange having high luminescence efficiency.
The europium doped MY2O4 nanomaterials were prepared by the rapid facile gel combustion procedure. High purity (99.9% purity) M(NO3)2
Prepared europium doped nanophosphor materials (3 mol% Eu3+). Without UV excitation source (a) MgY2O4:Eu3+, (b) CaY2O4:Eu3+, and (c) SrY2O4:Eu3+. With UV excitation (360 nm) (d) MgY2O4:Eu3+, (e) CaY2O4:Eu3+, and (f) SrY2O4:Eu3+.
Schematic flow diagram for the rapid facile gel combustion synthesis of MY2O4:Eu3+ (M = Mg, Ca, and Sr) nanophosphors.
The phase purity was determined by taking the XRD patterns using a Rigaku Ultima IV X-ray diffractometer with Cu Ka radiation (
XRD patterns of MY2O4:Eu3+ phosphors are presented in Figures
X-ray diffraction patterns of Eu3+ doped MgY2O4 nanophosphor.
X-ray diffraction patterns of Eu3+ doped CaY2O4 nanophosphor.
X-ray diffraction patterns of Eu3+ doped SrY2O4 nanophosphor.
The results of XRD patterns are summarized in Table
The morphology of these materials was analyzed using the scanning electron micrographs and transmission electron micrographs which are presented in Figures
SEM micrographs of prepared materials. (a) MgY2O4:Eu3+, (b) CaY2O4:Eu3+, and (c) SrY2O4:Eu3+.
TEM micrographs of (a) MgY2O4:Eu3+, (b) CaY2O4:Eu3+, and (c) SrY2O4:Eu3+ phosphors.
Sites occupied by Eu3+ ions in MY2O4 host lattice are a very interesting feature. Different arguments were given by different authors for the occupation of sites by Eu3+ ions. As energetically it is not easy for Eu3+ to substitute M2+ due to different valence states; but the size of Y3+ (1.04
Figures
Temperature dependent photoluminescence emission spectra of MgY2O4:Eu3+ phosphor.
Temperature dependent photoluminescence emission spectra of CaY2O4:Eu3+ phosphor.
Temperature dependent photoluminescence emission spectra of SrY2O4:Eu3+ phosphor.
Photoluminescence spectra of MY2O4:Eu3+ series of materials as prepared at 600°C.
The effect of sintering temperature on photoluminescent intensity is also investigated. Figures
Commission Internationale de l’Eclairage (CIE) in 1931 invented a set of three colour matching functions [
Showing the color coordinates of synthesized MY2O4:Eu3+ nanophosphors.
Phosphor compound | Colour coordinates | ||
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600°C | 800°C | 1100°C | |
MgY2O4:Eu3+ |
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CaY2O4:Eu3+ |
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SrY2O4:Eu3+ |
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Showing the calculated size of particles and structure of prepared MY2O4:Eu3+ nanophosphors.
Phosphor compound | 2 |
Crystal size (nm) | Matched JCPDS file number | Crystalline structure | ||
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All temperatures | 600°C | 800°C | 1100°C | |||
MgY2O4:Eu3+ | 30.6 | 25.64 | 41.03 | 52.36 | — | — |
CaY2O4:Eu3+ | 29.04 | 12.62 | 16.74 | 28.37 | 19–0265 | — |
SrY2O4:Eu3+ | 29.04 | 7.67 | 19.35 | 32.38 | 32–1272 | Orthorhombic |
Chromaticity diagram of prepared MY2O4:Eu3+ nanophosphors calcined at 1100°C. (a) MgY2O4:Eu3+, (b) CaY2O4:Eu3+, and (c) SrY2O4:Eu3+.
The series of red-orange light emitting phosphors, that is, MY2O4 (M used for Mg, Ca, and Sr), was successfully synthesized using a rapid facile gel combustion process using hexamethylenetetramine as an organic fuel. The XRD patterns confirmed the cubic structure of MgY2O4:Eu3+ as well as CaY2O4:Eu3+ phosphor and orthorhombic structure of SrY2O4:Eu3+. Crystal sizes obtained from TEM images of phosphors were found in nanorange and were found in good agreement with the sizes calculated from XRD patterns. Photoluminescence spectra of all these phosphors MY2O4:Eu3+ were provided emission at 612 nm. Emission intensity of SrY2O4:Eu3+ nanophosphor was found maximum than the other prepared materials of this series. On increasing calcination temperature, the luminescence intensity of these materials was also enhanced. XRD patterns showed the presence of single phase components at 600°C; on further calcination at higher temperature, crystallinity of phosphors was also increased. These prepared phosphors are having efficient light emitting properties that could be suitably used for various solid state lightening applications.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors gratefully recognize the financial support from the University Grants Commission (UGC), New Delhi [MRP-40-73/2011(SR)].