The synthesis of BaMgAl10O17:Eu2+ nanopowder by a combustion method and its luminescent properties View the table of contents for this issue, or go to the journal homepage for more 2011
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The synthesis of BaMgAl10O17:Eu2+ nanopowder by a combustion method and its luminescent properties
View the table of contents for this issue, or go to the journal homepage for more
2011 Adv Nat Sci: Nanosci Nanotechnol 2 045005
(http://iopscience.iop.org/2043-6262/2/4/045005)
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Adv Nat Sci.: Nanosci Nanotechnol 2 (2011) 045005 (4pp) doi:10.1088/2043-6262/2/4/045005
nanopowder by a combustion method and its luminescent properties
Manh Son Nguyen, Van Tuyen Ho and Nguyen Thuy Trang Pham
Department of Physics, College of Sciences, Hue University, 77 Nguyen Hue, Hue, Vietnam
E-mail:manhson03@yahoo.com
Received 27 April 2011
Accepted for publication 12 September 2011
Published 31 October 2011
Online atstacks.iop.org/ANSN/2/045005
Abstract
Europium ion doped BaMgAl10O17blue phosphor nanopowder has been fabricated by
urea–nitrate solution combustion synthesis at 590◦C for 5 min These phosphors were
codoped with different europium ion concentrations (1–8 mol%) The experimental results of
x-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence
showed that the phosphors have a hexagonal single phase structure, the average particle size of
the powders was about 50 nm and the emission spectra have a broad band with maximum
intensity at wavelengthλmax= 455 nm due to transitions from the 4f65d1to the 4f7electronic
configuration of Eu2+ion The maximum emission of phosphor corresponds to the europium
concentration 7 mol%
Keywords: phosphor, nanoparticle, combustion, photoluminescence
Classification numbers: 4.02, 4.04
1 Introduction
BaMgAl10O17:Eu2+blue phosphor has been used extensively
in manufacturing tricolor fluorescent lights (FL), field
emission displays (FED), plasma display panels (PDPs)
and liquid crystal displays (LCD) [1, 2] Emission spectra
of BaMgAl10O17:Eu2+ phosphor have a broad band with
peak at 455 nm due to transition from the 4f65d excited
state to the 4f7 ground state of ion Eu2+ There are
many synthesis technologies of this phosphor [3 6] Every
technology has some advantages Among them, combustion
synthesis has the following remarkable advantages: low
heating temperature and short reaction time However,
luminescent properties of materials depend strongly on
the technology conditions [2, 7] For BaMgAl10O17:Eu2+
phosphors prepared by urea–nitrate solution combustion
synthesis, urea plays the role of fuel as well as reducing agent
Besides, the initiating combustion temperature influences the
product In the present experimental work, we study the
influence of urea concentration and the initiating combustion
temperature on luminescent properties of BaMgAl10O17:
Eu2+phosphors prepared by urea–nitrate solution combustion
synthesis, and also the influence of concentration on emission intensity
2 Experimental
Starting materials for the preparation of BaMgAl10O17:Eu2+ phosphors by urea–nitrate solution combustion synthesis are
a mixture of Ba(NO3)2, Mg(NO3)2· 6H2O, Al(NO3)3· 9H2O and Eu2O3 oxide Urea was used to supply fuel and reducing agent Eu2O3oxide has been nitrified by nitric acid The reaction for the formation of BaMgAl10O17:Eu2+, assuming complete combustion, may be written as
(1 − x)Ba(NO3)2+ xEu(NO3)3+ Mg(NO3)2+ 10Al(NO3)3+
28.34CH4N2O → Ba(1−x)EuxMgAl10O17+ by products [8] Aqueous solution containing stoichiometric amounts of nitrate metal and urea was mixed by a magnetic stirrer and heated at 60◦C for 2 h to gel Next, the gel was dried at 80◦C
to dehydrate and combusted at different temperatures within
5 min The product was BaMgAl10O17:Eu2+ (1 mol%) with white powder The influence of heating temperature and urea concentration on luminescent properties was investigated The samples were prepared with combustion temperature changed
Trang 3Adv Nat Sci.: Nanosci Nanotechnol 2 (2011) 045005 M S Nguyen et al
0
100
200
300
400
: B a M g A l10O17
•
↓
•
•
•
•
•
•
•
•
•
•
•
•
•
60 70
50
40
30
2 θ (D eg )
↓
Figure 1 XRD diagram of the samples with different
concentrations of urea
0.0
0.5
1.0
1.5
2.0
(6)
(4)
(2)
(1) n = 30 (2) n = 40 (3) n = 50 (4) n = 60 (5) n = 70 (6) n = 80
(1)
(5) (3)
Wavelength (nm)
Figure 2 Emission spectra of phosphors prepared with different
concentrations of urea
from 570 to 630◦C, concentration of Eu2+ions changed from
0 to 8 mol% and changing the urea mole (nurea) from 30 to 80
times the product mole (nBAM) For convenience, we set
n = nurea
nBAM
,
in this case 30 6 n 6 80.
3 Results and discussions
3.1 The effects of combustion technology on the structure
and luminescence ofBaMgAl10O17:Eu2+blue phosphor
The crystallographic phase of phosphor with different urea
concentrations at a constant combustion temperature of
590◦C was confirmed by x-ray diffraction (XRD) and the
results are shown in figure1 The XRD pattern indicated that
product did not appear at BaMgAl10O17 phase with n = 30.
With n = 40, 50 and 70, products occurred at a low amount
of undesirable phase beside the BaMgAl10O17 phase The
material had a hexagonal single phase structure with n = 60.
Luminescent spectra of BaMgAl10O17:Eu2+ phosphors
prepared with different concentrations of urea are shown in
figure2 Emissions of phosphors with concentrations n = 40,
50, 60 and 70 have a broad band with peak at 455 nm that
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
I PLm
Urea concentration, n (mol)
ions as a function of urea concentration
•
↓
θ
•
•
•
•
•
•
•
•
•
•
•
•
•
↓
Figure 4 XRD diagram of the samples at different combustion
temperatures
characterized the transition of electronic configuration from the 4f65 d excited state to the 4f7ground state of Eu2+ions
The emission of the sample with n = 30 has weak
luminescent intensity, the emission maximum shifts to a longer wavelength and emission also exists at 617 nm of
Eu3+ ions It showed that the low concentration of urea did
not suffice for the complete reduction Besides, with n = 80,
the luminescent intensity is very low and the position of maximum radiation intensity shifts to a longer wavelength region
Figure 3 shows the change of maximum luminescent intensity of the phosphors as a function of urea concentration
The phosphor with n = 60 was not only a single-phase
structure but also has a better intensity of luminescence than the other samples
From the investigated results of the XRD patterns, the
invariable concentration of urea were chosen as n = 60
to synthesize the phosphor at different combustion temperatures Their XRD diagrams are presented in figure4
It shows that samples had a hexagonal single-phase structure when the combustion temperature was at 590◦C At other temperatures, the structure of the materials appeared not only
in BaMgAl10O17phase but also in another sub-phase Luminescent spectra of the phosphors prepared with variable combustion temperature and constant
2
Trang 4Adv Nat Sci.: Nanosci Nanotechnol 2 (2011) 045005 M S Nguyen et al
0.0
0.5
1.0
(2) 590 0 C (3) 610 0 C (4) 630 0 C (2)
(3)
(4) (1)
Wavelength (nm)
Figure 5 Emission spectra of phosphor with different heating
temperatures
0.5
1.0
1.5
Temperature (oC)
Figure 6 The dependence of maximum intensity as a function of
combustion temperature
urea concentration are presented in figure 5 Broadband
luminescent spectra of the samples characterized the
transition of Eu2+ ions with maximum luminescent intensity
at 455 nm wavelength However, the luminescent spectra also
show a low broadband emission with maximum wavelength
at 520 nm when the sample was heated at a temperature of
570◦C This suggests that the structure of this phosphor also
exists in some unwanted phase, when heating temperature
is not appropriate Auxiliary emission band could be
Eu2+ion concentration
concentration
the radiation of ion Eu2+ in this lattice The change of luminescent intensity of the phosphors BaMgAl10O17:Eu2+
on the heating temperature is described in figure 6 The results show that the heated sample at 590◦C had the highest luminescent intensity
A SEM image of the samples is shown in figure7 The average particle size of the powder is about 50 nm However, the particle distribution is not uniform
3.2 The effect of concentration of E u2+ions on luminescent characteristics
Phosphors BaMgAl10O17:Eu2+ with activator concentration ranging from 0 to 8 mol% were prepared by the combustion
of corresponding metal nitrates and urea solution with urea
concentration 60 nBAM at 590◦C The prepared phosphors had a single phase structure Luminescent spectra of the phosphors were recorded by exciting at 365 nm and are presented in figure8 It shows that relative emission intensity increased with increasing activator concentration Eu2+but the emission maximum did not change Above 7 mol% Eu2+ion,
a sudden drop of relative intensity was observed, probably due to concentration quenching In figure 9, the optimum activator concentration was found to be 7 mol% for maximum emission intensity
Trang 5Adv Nat Sci.: Nanosci Nanotechnol 2 (2011) 045005 M S Nguyen et al
4 Conclusion
The urea concentration and combustion temperature in the
combustion technology influenced the crystalline structure
and optical properties of the products BaMgAl10O17:
Eu2+ phosphor nanopowder was prepared by a urea–nitrate
solution combustion method Nanosized blue phosphor
BaMgAl10O17:Eu2+ had a single hexagonal structure phase
that was synthesized with n = 60 and combustion temperature
590◦C Note that the value n = 28.33 was derived from
the theoretical calculation in [8] With the increase of
Eu2+ concentration, the emission intensity increased but the
maximum of the spectra did not change The optimum
concentration of Eu2+ ions was 7 mol% in order to achieve
the highest emission
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