JOURNAL OF SCIENCE, Hue University, Vol. 69, No. 6, 2011<br />
<br />
SYNTHESIS OF BaMgAl10O17: Eu2+ BLUE PHOSPHOR<br />
BY COMBUSTION METHOD<br />
Nguyen Manh Son, Ho Van Tuyen, Pham Nguyen Thuy Trang<br />
College of Sciences, Hue University<br />
<br />
Abstract. Europium ion doped BaMgAl10O17 blue phosphors have been prepared by ureanitrate solution combustion synthesis at 590 0C for 5 minutes. The experimental results of<br />
XRD, SEM and photoluminescent spectra showed that the phosphors had hexagonal single<br />
phase structure, the average particle size of the powders was about 50 nm and the emission<br />
spectra was a broad band with maximum intensity at the wavelength λmax = 455 nm due to<br />
transitions from 4f65d1 to the 4f7 electronic configuration of Eu2+ ion.<br />
<br />
1<br />
<br />
Introduction<br />
<br />
BaMgAl10O17: Eu2+ blue phosphor has been used extensively in manufacturing tricolor<br />
fluorescent lights (FL), field emission displays (FED), plasma display panels (PDPs)<br />
and liquid crystal displays (LCD) [1, 2]. Emission spectra of BaMgAl10O17: Eu2+<br />
phosphor was a broad band with peak at 455nm due to transition from the 4f65d excited<br />
state to the 4f7 ground state of ion Eu2+. There are many synthesis technologies of this<br />
phosphor [3, 4, 5, 6]. Every technology has some advantages. Among them,<br />
combustion synthesis has many remarkable advantages as: low heating temperature,<br />
short reaction time. However, luminescent properties of materials depend greatly on the<br />
technology conditions [2, 7]. For BaMgAl10O17: Eu2+ phosphors prepared by urea nitrate solution combustion synthesis, urea plays the role of fuel just as the reducing<br />
agent. Besides, the initiating combustion temperature influences the product. In this<br />
report, the experimental results determine the influence of urea concentration and the<br />
initiating combustion temperature on luminescent properties and structure of<br />
BaMgAl10O17: Eu2+ phosphors prepared by urea - nitrate solution combustion synthesis.<br />
<br />
2<br />
<br />
Experiments<br />
<br />
To prepare BaMgAl10O17: Eu2+ phosphors by urea - nitrate solution combustion<br />
synthesis, starting materials are the mixture of Ba(NO3)2, Mg(NO3)2.6H2O,<br />
Al(NO3)3.9H2O and Eu2O3 oxide. Urea was used to supply fuel and reduce agent.<br />
Eu2O3 oxide has been nitrified by nitric acid. Theoretical equation for formation of<br />
BaMgAl10O17: Eu2+, assuming complete combustion, may be written as:<br />
95<br />
<br />
(1 − x)Ba(NO3)2 + xEu(NO3)3 + Mg(NO3)2 + 10Al(NO3)3<br />
Ba(1−x)EuxMgAl10O17 + by products.<br />
<br />
+28.34CH4N2O (urea) →<br />
<br />
The aqueous solution containing stoichiometric amounts of nitrate metal and<br />
urea was mixed by magnetic stirrer and heated at 60oC for 2 hours to gel. Next, the gel<br />
was dried at 80oC to dehydrate and combusted at different temperatures within 5<br />
minutes, the product obtained was BaMgAl10O17: Eu2+ (1% mol) with white powder.<br />
The influence of heating temperature and urea concentration on luminescent properties<br />
had been investigated that the samples BAM were prepared with changing of urea mole<br />
(nurea) from 30 to 80 times product mole (nBAM), combustion temperature could be<br />
change from 570 oC to 630 oC.<br />
<br />
3<br />
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Results and discussions<br />
<br />
The crystallographic phase of phosphor with changed urea concentration at the constant<br />
combustion temperature 590oC was confirmed by X-ray diffraction (XRD), the results<br />
were shown in Fig. 1. XRD pattern indicated that the product didn’t appear to be<br />
BaMgAl10O17 phase with nurea = 30 nBAM. With nurea = 40, 50 and 70 nBAM, products<br />
occurred a low amount of undesirable phase beside BaMgAl10O17 phase. Material had<br />
hexagonal single phase structure with nurea = 60 nBAM.<br />
: BaMgAl10 O 17<br />
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2 (Deg)<br />
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Fig. 1. X-ray diffraction diagram of the samples with different concentrations of urea.<br />
<br />
Luminescent spectra of BAM phosphors with different concentration of urea<br />
were showed in Fig. 2. Emission of phosphors with concentrations nurea = 40, 50, 60, 70<br />
was a broad band with peak at 455nm that characterized transition of electronic<br />
configuration from the 4f65d excited state to the 4f7 ground state of ion Eu2+.<br />
The emission of sample with nurea = 30 nBAM has a weak luminescent intensity,<br />
emission maximum shifts to longer wavelength and exists the emission at 617 nm of<br />
Eu3+ ions. It was shown that the low concentration of urea did not suffice for the<br />
complete reduction. Besides, with nurea = 80, the luminescent intensity is very low and<br />
the position of maximum radiation intensity shifted to longer wavelength region.<br />
96<br />
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2.0<br />
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2.0<br />
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(4)<br />
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IPLmax(a. u.)<br />
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Intensity PL (a. u.)<br />
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(1) n = 30<br />
(2) n = 40<br />
(3) n = 50<br />
(4) n = 60<br />
(5) n = 70<br />
(6) n = 80<br />
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Wavelength (nm)<br />
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50<br />
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80<br />
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Urea concentration, n (mol)<br />
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Fig. 2. Emission spectra of BAM phosphors<br />
with different concentrations of urea.<br />
<br />
Fig. 3. The dependence of maximum emission<br />
intensity of Eu2+ ion as the function of urea<br />
concentration.<br />
<br />
Fig. 3 describes the change of maximum luminescent intensity of the phosphors<br />
as a function of urea concentration nurea. The phosphor with nurea = 60 was not only<br />
single-phase structure but also the intensity of luminescence better than other samples.<br />
: B a M g A l10O 17<br />
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570 C<br />
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2 (D e g )<br />
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Fig. 4. X-ray diffraction diagram of the BAM samples at different combustion temperature.<br />
<br />
From the results of the investigation of the X-ray diffraction patterns for the<br />
BAM samples, the invariable concentration of urea had been chosen nurea = 60 to<br />
synthesis at different combustion temperature. Their XRD diagrams were presented in<br />
Fig. 4. It was shown that the sample had the hexagonal single-phase structure when the<br />
combustion temperature was at 590°C. At the other temperatures, the structure of the<br />
materials appeared not only BaMgAl10O17 phase but also another sub-phase.<br />
<br />
97<br />
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0<br />
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(1) 570 C<br />
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(2) 590 C<br />
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(3) 610 C<br />
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(4) 630 C<br />
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(2)<br />
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1.5<br />
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Intensity PL (a. u.)<br />
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Intensity PL (a.u)<br />
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Wavelength (nm)<br />
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Temperature ( C)<br />
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Fig. 5. Emission spectra of BAM phosphor<br />
with different heating temperature.<br />
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Fig. 6. The dependence of the maximum<br />
intensity as a function of combustion<br />
temperature.<br />
<br />
Luminescent spectra of the phosphors when the variable combustion<br />
temperature and constant urea concentration were presented in Fig. 5. Broadband<br />
luminescent spectra of the samples characterized to transition of Eu2+ ion, the maximum<br />
luminescent intensity at 455 nm wavelength. However, the luminescent spectra appear<br />
also a low broadband emission with maximum wavelength at 520 nm when sample was<br />
heated at the temperature 570 oC. This suggests that the structure of this phosphor also<br />
exists the unwanted phase, when heating temperature is not appropriate. Auxiliary<br />
emission band could be radiati on of ion Eu2+ in this lattice. The change of luminescent<br />
intensity of the phosphors BAM: Eu2+ on the heating temperature was described in Fig.<br />
6. The results showed that the heated sample at 590oC had the highest luminescent<br />
intensity.<br />
<br />
Fig. 7. SEM image of BAM: Eu2+<br />
<br />
SEM image of BAM shows in Fig. 7. The average particle size of the powder is<br />
about 50nm. However, the distribution is not uniform particles.<br />
98<br />
<br />
4<br />
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Conclusion<br />
<br />
Urea concentration and combustion temperature in the combustion technology greatly<br />
influenced the crystalline structure and optical properties of the products. BaMgAl10O17:<br />
Eu2+ phosphors were prepared by the urea - nitrate solution combustion method.<br />
Nanosized blue phosphor BAM: Eu2+ had hexagonal single phase structure that was<br />
synthesised with nurea = 60 nBAM (theory 28.33) and combustion temperature 590oC.<br />
References<br />
1. R. S. Yadav, Sh. K. Pandey, A. Ch. Pandey. Blue –shift and enhanced<br />
photoluminescence in BaMgAl10O17: Eu2+ nanophosphor under VUV excitation for<br />
PDPs aplication. Materials Sciences and Applications. Vol. 1, (2010), 25-31.<br />
2. Zhe Chenm, Youwei Yan. Nano – sized PDP phosphors prepared by combustion<br />
method. J. Mater. Sci. 40, (2006), 5793-5796<br />
3. Young Kyu Jeong, Hyug-Jong Kim, Hee Gyu Kim, Byung-Ho Choi. Luminescent<br />
properties of BaMgAl10O17:Eu2+ blue phosphor grown with SiO2 using atomic layer<br />
deposition. Current Applied Physics. 9, (2009), 249-251.<br />
4. A. Dulda, D. S. Jo, W. J. Park, T. Masaki and D. H. Yoon. Photoluminescence and<br />
morphology of flux grown BAM phosphor using a novel synthesis method. Journal of<br />
Ceramic Processing Research, Vol. 10, No. 6, (2009), 811-816.<br />
5. C. W. Won, H. H. Nersisyan, H. I. Won, S. J. Kwon, H. Y. Kim, S. Y. Seo, Synthesis of<br />
nano-size BaMgAl10O17:Eu2+ blue phosphor by a rapid exothermic reaction, J. Lum.<br />
Vol. 130 (4), (2009), 678-681.<br />
6. Chung-Hsin Lu, Chung-Tao Chen, Baibaswata Bhattacharjee, Sol-gel preparation and<br />
luminescence properties of BaMgAl10O17: Eu2+ phosphor, Journal of Rare Earths, Vol.<br />
24, (2006), 706-711.<br />
7. Zhe Chen, Youwei Yan, Junming Liu, Yi Yin, HongminWen, Jiangqian Zao, Dehui Liu,<br />
Hongmin Tian, Chenshu Zhang, Shuidi Li, Microwave induced solution combustion<br />
synthesis of nano-sized phosphors, Journal of Alloys and Compounds, L13-L16,<br />
(2009), 473.<br />
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