The present paper reports the effect of europium concentration on photoluminescence (PL) and thermoluminescence (TL) studies of Eu3+ doped Y4Al2O9 phosphor using inorganic materials like yttrium oxide (Y2O3), aluminium oxide (Al2O3), boric acid (H3BO3) as a flux, and europium oxide (Eu2O3). 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 X-ray diffraction (XRD), field emission gun scanning electron microscopy (FEGSEM), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL), thermoluminescence (TL), and CIE techniques. The PL emission was observed in the range of 467, 535, 591, 611, 625, and 629 nm for the Y4Al2O9 phosphor doped with Eu3+ (0.1 mol% to 2.5 mol%). Excitation spectrum was found at 237 and 268 nm. Sharp peaks were found around 591, 611, and 625 nm with high intensity. From the XRD data, using Scherer’s formula, the calculated average crystallite size of Eu3+ doped Y4Al2O9 the phosphor is around 55 nm. Thermoluminescence study was carried out for the phosphor with UV irradiation. The present phosphor can act as single host for red light emission in display devices.
During the past decades, nanostructured materials have attracted considerable attention for their novel and enhanced properties; for example, the Mn doped ZnS phosphor can yield both high luminescent efficiencies and short lifetime [
The Y2O3-Al2O3 system is a promising material for refractory coatings and for ceramic and semiconductor processing technology [
In this paper, a new modified solid state reaction method was used to synthesize Y4Al2O9:Eu3+ phosphor. This process perfectly combines the merits of solid state reaction processing and a high-temperature combustion process. This synthesis has the advantages of inexpensive precursors, convenient process control, and large mass production. The Y4Al2O9:Eu3+ phosphor was synthesized at a high temperature of 1300°C. The structure, morphology, photoluminescence, and thermoluminescence study of Y4Al2O9:Eu3+ phosphor is investigated in detail.
To prepare Y4Al2O9 with various concentrations of europium (0.1 moL% to 2.5 moL%), consisting, heating in stoichiometric amounts of reactant mixture are taken in alumina crucible and fired in air at 1000°C for 1 hour in a muffle furnace. Every heating is followed by intermediate grinding using agate mortar and pestle. The Eu3+ activated Y4Al2O9 phosphor was prepared via high temperature modified solid state diffusion. The starting materials were as follows: Y2O3, Al2O3 Eu2O3, and H3BO3 (as a flux) in molar ratio (0.1% to 2.5% of Eu) were used to prepare the phosphor. The mixture of reagents was ground together to obtain a homogeneous powder. After being ground thoroughly in stoichiometric ratios by using an agate mortar by dry grinding for nearly 45 minutes, to ensure the best homogeneity and reactivity, powder was transferred to alumina crucible and then heated in a muffle furnace at 1300°C for 4 hours [
The sample was characterized using XRD, FTIR, EDX (energy dispersive X-ray analysis) FEGSEM, and HRTEM. The XRD measurements were carried out using Bruker D8 Advance X-ray diffractometer. The X-rays were produced using a sealed tube and the wavelength of X-ray was 0.154 nm (Cu K-alpha). The X-rays were detected using a fast counting detector based on Silicon strip technology (Bruker LynxEye detector).Observation of particle morphology was investigated by FEGSEM (field emission gun scanning electron microscope) (JEOL JSM-6360). The photoluminescence (PL) emission and excitation spectra were recorded at room temperature by use of a Shimadzu RF-5301 PC spectrofluorophotometer. The excitation source was a xenon lamp. Thermally stimulated luminescence glow curves were recorded at room temperature by using TLD reader I1009 supplied by Nucleonix Sys. Pvt. Ltd. Hyderabad [
The XRD pattern of the sample is shown in Figure
PXRD pattern of Eu3+ doped Y4Al2O9 phosphor (1.5% Eu).
Here D is particle size,
For XRD pattern corresponding miller indices values are calculated which match with JCPDS card no. as shown in Figure
Figures
((a)–(e)) FEGSEM image of prepared phosphor with different resolutions (1.5% Eu).
Figures
((a)–(c)) HRTEM image of prepared phosphor with different resolutions (1.5% Eu).
It is an elemental analysis of prepared phosphor. Figure
EDX of Eu3+ doped Y4Al2O9 phosphor (1.5% Eu).
FTIR spectrum of Y4Al2O9:Eu powder is shown in the Figure
FTIR spectra of Y4Al2O9:Eu doped phosphor.
Figures
PL excitation spectra of Y4Al2O9:Eu (0.1%) doped phosphor excited with 612 nm.
Figure
PL spectra of Y4Al2O9:Eu doped phosphor with variation of Eu concentrations excited with 237 nm.
PL excitation spectra of Y4Al2O9:Eu (1.5%) doped phosphor excited with 612 nm.
The strong emission peak of Y4Al2O9:Eu3+ phosphor is due to forced electric dipole transition of 5D0 to 7F2 centered at 611 nm. It is characteristic red emission. The Y4Al2O9 phase crystallizes in monoclinic system with space group P21/c. Then Eu3+ ions with C2h point symmetry are in the strict inversion center. Therefore, the phosphor should mainly exhibit the orange
The emission spectrum of phosphors was recorded by excitations with 237 nm and 265 nm. The emission spectrum is shown in Figures
PL emission intensities for different excitations.
S. number | Sample name |
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Intensity |
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1 | Y4Al2O9:Eu (0.1%) | 254 | 468, 594, 612, 624 | 46, 42, 17, 14 |
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2 | Y4Al2O9:Eu (0.2%) | 254 | 468, 583, 591, 612, 624, 629 | 72, 55, 69, 121, 71, 62 |
265 | 468, 583, 591, 612, 624 | 67, 26, 35, 53, 27 | ||
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3 | Y4Al2O9:Eu (0.5%) | 265 | 468, 583, 591, 612, 624, 629 | 68, 95, 123, 247, 162, 147 |
254 | 468, 583, 591, 612, 624, 629 | 74, 91, 112, 189, 125, 115 | ||
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4 | Y4Al2O9:Eu (1%) | 254 | 468, 583, 591, 612, 624, 629 | 76, 90, 122, 269, 136, 124 |
265 | 468, 583, 591, 612, 624, 629 | 76, 183, 260, 599, 352, 316 | ||
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5 | Y4Al2O9:Eu (1.5%) | 265 | 468, 583, 591, 612, 624, 629 | 69, 158, 222, 504, 318, 277 |
254 | 468, 583, 591, 612, 624, 629 | 93, 157, 204, 527, 256, 223 | ||
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6 | Y4Al2O9:Eu (2%) | 254 | 468, 583, 591, 612, 624, 629 | 95, 129, 181, 436, 221, 193 |
265 | 468, 583, 591, 612, 624 | 67, 26, 35, 53, 27 | ||
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7 | Y4Al2O9:Eu (2.5%) | 254 | 468, 583, 591, 612, 624, 629 | 65, 141, 223, 454, 229, 213 |
PL spectra of Y4Al2O9:Eu doped phosphor with variation of Eu concentrations excited with 265 nm.
PL spectra of Y4Al2O9:Eu doped phosphor Eu (1.5 moL%) excited with 265 nm.
Figures
TL glow curve of Eu3+ doped Y4Al2O9 phosphor variation with Eu concentration for 5 min UV.
TL glow curve of Eu3+ doped Y4Al2O9 phosphor variation with Eu concentration for 10 min UV.
TL glow curve of Eu3+ doped Y4Al2O9 phosphor variation with Eu concentration for 15 min UV.
According to experimental results here described, the presence of transition metal ions changes the TL glow curve structure either enhancing or quenching the TL efficiency. These changes are a consequence of the crystalline field perturbation due to the different characteristics of the dopant ions which supposedly replaces the yttrium sites. The traps and the glow curve structure are also dependent upon the morphology of the surface area which in turn depends on the nanocrystallite size. The nanocrystallite size depends also on the dopant ion. Furthermore, the obtained experimental results show that the presence of dopant ions also modifies the TL recombination efficiency which was found to be different for each irradiation type and the specific exposed material. It is important to notice that using the right dopant concentration, it is possible to maximize the TL efficiency and improve sensitivity and dose linearity for a specific irradiation type.
Thermoluminescence (TL) phosphors generally exhibit glow curves with one or more peaks when the charge carriers are released. The glow curve is characteristic of the different trap levels that lie in the band gap of the material. The traps are characterized by certain physical parameters that include trap depth (
In this work, Chen’s method [
Order of kinetics depends on the glow peak shape. The value of
For the first order kinetics, the Balarin parameter (
The activation energy (
Shape factors (
Eu concentration |
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Activation energy ( |
Frequency factor(s) |
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0.1% Eu | 64 | 94 | 124 | 30 | 30 | 60 | 0.5 | 0.58 |
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0.2% Eu | 96 | 127 | 157 | 31 | 30 | 61 | 0.49 | 0.66 |
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1% Eu | 60 | 87 | 125 | 27 | 38 | 65 | 0.58 | 0.63 |
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1.5% Eu | 87 | 119 | 161 | 32 | 42 | 74 | 0.56 | 0.63 |
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2% Eu | 96 | 129 | 168 | 33 | 39 | 72 | 0.54 | 0.64 |
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2.5% Eu | 87 | 117 | 151 | 30 | 34 | 64 | 0.53 | 0.66 |
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The CIE coordinates were calculated by spectrophotometric method using the spectral energy distribution of the Y4Al2O9:Eu3+ sample (Figure
CIE coordinates depicted on 1931 chart where
Y4Al2O9:Eu3+ phosphor powder was successfully synthesized using a modified solid state method. XRD studies confirm that the phosphors are in single phase and nanocrystallites. Y4Al2O9:Eu3+ (1.5%) phosphor shows an orange-red emission under 254 nm excitation. The photoluminescence study shows that the emission intensity of electric dipole transition (612 and 624 nm) (5D0
The Y4Al2O9 phase was quenched in favor of the red emission of Eu3+ ions indicating that europium must be close to yttrium aluminate monoclinic host for better host to Eu energy transfer. However, under 254 nm excitation, Eu (1.5%) doped Y4Al2O9 phosphor shows high intensity. The PL studies concluded that Y4Al2O9:Eu3+ doped phosphor under 254 nm excitation can act as a single host for producing orange-red light with good intensity for all practical display devices in particular fluorescent lamps and CFLs. In thermoluminescence study, maximum peaks show second order kinetics which means that more than one luminescent center is present in the phosphor sample. Sample shows very good TL glow curve. TL glow curve was analyzed and the trap depths for the two luminescence centers 119 and 276°C glow peaks were calculated. Hence this phosphor may find use in radiation dosimetry.
The authors declare that there is no conflict of interests regarding the publication of this paper.