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Adv. Nat. Sci.: Nanosci. Nanotechnol. 2 (2011) 045005 (4pp) doi:10.1088/2043-6262/2/4/045005

The synthesis of BaMgAl10O17:Eu2+

nanopowder by a combustion method andits luminescent propertiesManh 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 2011Accepted for publication 12 September 2011Published 31 October 2011Online at stacks.iop.org/ANSN/2/045005

AbstractEuropium ion doped BaMgAl10O17 blue phosphor nanopowder has been fabricated byurea–nitrate solution combustion synthesis at 590 ◦C for 5 min. These phosphors werecodoped with different europium ion concentrations (1–8 mol%). The experimental results ofx-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescenceshowed that the phosphors have a hexagonal single phase structure, the average particle size ofthe powders was about 50 nm and the emission spectra have a broad band with maximumintensity at wavelength λmax = 455 nm due to transitions from the 4f65d1 to the 4f7 electronicconfiguration of Eu2+ ion. The maximum emission of phosphor corresponds to the europiumconcentration 7 mol%.

Keywords: phosphor, nanoparticle, combustion, photoluminescence

Classification numbers: 4.02, 4.04

1. Introduction

BaMgAl10O17 :Eu2+ blue phosphor has been used extensivelyin manufacturing tricolor fluorescent lights (FL), fieldemission displays (FED), plasma display panels (PDPs)and liquid crystal displays (LCD) [1, 2]. Emission spectraof BaMgAl10O17 :Eu2+ phosphor have a broad band withpeak at 455 nm due to transition from the 4f65d excitedstate to the 4f7 ground state of ion Eu2+. There aremany synthesis technologies of this phosphor [3–6]. Everytechnology has some advantages. Among them, combustionsynthesis has the following remarkable advantages: lowheating temperature and short reaction time. However,luminescent properties of materials depend strongly onthe technology conditions [2, 7]. For BaMgAl10O17 :Eu2+

phosphors prepared by urea–nitrate solution combustionsynthesis, urea plays the role of fuel as well as reducing agent.Besides, the initiating combustion temperature influences theproduct. In the present experimental work, we study theinfluence of urea concentration and the initiating combustiontemperature on luminescent properties of BaMgAl10O17 :Eu2+ phosphors prepared by urea–nitrate solution combustion

synthesis, and also the influence of concentration on emissionintensity.

2. Experimental

Starting materials for the preparation of BaMgAl10O17 :Eu2+

phosphors by urea–nitrate solution combustion synthesis area mixture of Ba(NO3)2, Mg(NO3)2 · 6H2O, Al(NO3)3 · 9H2Oand Eu2O3 oxide. Urea was used to supply fuel andreducing agent. Eu2O3 oxide 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)Eux MgAl10O17+ by products [8].

Aqueous solution containing stoichiometric amounts ofnitrate metal and urea was mixed by a magnetic stirrer andheated at 60 ◦C for 2 h to gel. Next, the gel was dried at 80 ◦Cto dehydrate and combusted at different temperatures within5 min. The product was BaMgAl10O17 :Eu2+ (1 mol%) withwhite powder. The influence of heating temperature and ureaconcentration on luminescent properties was investigated. Thesamples were prepared with combustion temperature changed

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Adv. Nat. Sci.: Nanosci. Nanotechnol. 2 (2011) 045005 M S Nguyen et al

20 30 40 50 60 700

100

200

300

400

: BaMgAl10

O17

•

↓

•••••••••

•••••

••

60

70

50

40

30

Lin

(Cps

)

2θ (Deg)

↓

Figure 1. XRD diagram of the samples with differentconcentrations of urea.

400 450 500 550 600 650

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)

Inte

nsi

ty P

L (

a. u

.)

Wavelength (nm)

Figure 2. Emission spectra of phosphors prepared with differentconcentrations of urea.

from 570 to 630 ◦C, concentration of Eu2+ ions changed from0 to 8 mol% and changing the urea mole (nurea) from 30 to 80times the product mole (nBAM). For convenience, we set

n =nurea

nBAM,

in this case 306 n 6 80.

3. Results and discussions

3.1. The effects of combustion technology on the structureand luminescence of BaMgAl10O17 :Eu2+ blue phosphor

The crystallographic phase of phosphor with different ureaconcentrations at a constant combustion temperature of590 ◦C was confirmed by x-ray diffraction (XRD) and theresults are shown in figure 1. The XRD pattern indicated thatproduct did not appear at BaMgAl10O17 phase with n = 30.With n = 40, 50 and 70, products occurred at a low amountof undesirable phase beside the BaMgAl10O17 phase. Thematerial had a hexagonal single phase structure with n = 60.

Luminescent spectra of BaMgAl10O17 :Eu2+ phosphorsprepared with different concentrations of urea are shown infigure 2. Emissions of phosphors with concentrations n = 40,50, 60 and 70 have a broad band with peak at 455 nm that

30 40 50 60 70 80

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

I PLm

ax(

a. u.)

Urea concentration, n (mol)

Figure 3. The dependence of maximum emission intensity of Eu2+

ions as a function of urea concentration.

•

↓

θ

•••••••••

•••

••

••

↓

Figure 4. XRD diagram of the samples at different combustiontemperatures.

characterized the transition of electronic configuration fromthe 4f65 d excited state to the 4f7 ground state of Eu2+ ions.

The emission of the sample with n = 30 has weakluminescent intensity, the emission maximum shifts to alonger wavelength and emission also exists at 617 nm ofEu3+ ions. It showed that the low concentration of urea didnot suffice for the complete reduction. Besides, with n = 80,the luminescent intensity is very low and the position ofmaximum radiation intensity shifts to a longer wavelengthregion.

Figure 3 shows the change of maximum luminescentintensity of the phosphors as a function of urea concentration.The phosphor with n = 60 was not only a single-phasestructure but also has a better intensity of luminescence thanthe other samples.

From the investigated results of the XRD patterns, theinvariable concentration of urea were chosen as n =60to synthesize the phosphor at different combustiontemperatures. Their XRD diagrams are presented in figure 4.It shows that samples had a hexagonal single-phase structurewhen the combustion temperature was at 590 ◦C. At othertemperatures, the structure of the materials appeared not onlyin BaMgAl10O17 phase but also in another sub-phase.

Luminescent spectra of the phosphors preparedwith variable combustion temperature and constant

2

Adv. Nat. Sci.: Nanosci. Nanotechnol. 2 (2011) 045005 M S Nguyen et al

350 400 450 500 550 600 650 700

0.0

0.5

1.0

1.5 (1) 570 0C (2) 590 0C (3) 610 0C (4) 630 0C

(2)

(3)

(4)

(1)

Inte

nsity

PL

(a.u

)

Wavelength (nm)

Figure 5. Emission spectra of phosphor with different heatingtemperatures.

580 600 620

0.5

1.0

1.5

Inte

nsity

PL

(a.

u.)

Temperature (oC)

Figure 6. The dependence of maximum intensity as a function ofcombustion temperature.

Figure 7. SEM image of BaMgAl10O17.

urea concentration are presented in figure 5. Broadbandluminescent spectra of the samples characterized thetransition of Eu2+ ions with maximum luminescent intensityat 455 nm wavelength. However, the luminescent spectra alsoshow a low broadband emission with maximum wavelengthat 520 nm when the sample was heated at a temperature of570 ◦C. This suggests that the structure of this phosphor alsoexists in some unwanted phase, when heating temperatureis not appropriate. Auxiliary emission band could be

Figure 8. Emission spectra of BaMgAl10O17 :Eu2+ with variableEu2+ ion concentration.

Figure 9. The plot of emission intensity as a function of Eu2+ ionconcentration.

the radiation of ion Eu2+ in this lattice. The change ofluminescent intensity of the phosphors BaMgAl10O17 :Eu2+

on the heating temperature is described in figure 6. Theresults show that the heated sample at 590 ◦C had the highestluminescent intensity.

A SEM image of the samples is shown in figure 7. Theaverage particle size of the powder is about 50 nm. However,the particle distribution is not uniform.

3.2. The effect of concentration of Eu2+ ions on luminescentcharacteristics

Phosphors BaMgAl10O17 :Eu2+ with activator concentrationranging from 0 to 8 mol% were prepared by the combustionof corresponding metal nitrates and urea solution with ureaconcentration 60 nBAM at 590 ◦C. The prepared phosphorshad a single phase structure. Luminescent spectra of thephosphors were recorded by exciting at 365 nm and arepresented in figure 8. It shows that relative emission intensityincreased with increasing activator concentration Eu2+ but theemission maximum did not change. Above 7 mol% Eu2+ ion,a sudden drop of relative intensity was observed, probablydue to concentration quenching. In figure 9, the optimumactivator concentration was found to be 7 mol% for maximumemission intensity.

3

Adv. Nat. Sci.: Nanosci. Nanotechnol. 2 (2011) 045005 M S Nguyen et al

4. Conclusion

The urea concentration and combustion temperature in thecombustion technology influenced the crystalline structureand optical properties of the products. BaMgAl10O17 :Eu2+ phosphor nanopowder was prepared by a urea–nitratesolution combustion method. Nanosized blue phosphorBaMgAl10O17 :Eu2+ had a single hexagonal structure phasethat was synthesized with n = 60 and combustion temperature590 ◦C. Note that the value n = 28.33 was derived fromthe theoretical calculation in [8]. With the increase ofEu2+ concentration, the emission intensity increased but themaximum of the spectra did not change. The optimumconcentration of Eu2+ ions was 7 mol% in order to achievethe highest emission.

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