TL Glow Curve Study, Kinetics, PL and XRD Analysis of Mn2+ Doped CaAl2O4 Phosphors

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Journal of Minerals and Materials Characterization and Engineering, 2012, 11, 1081-1084

Published Online November 2012 (http://www.SciRP.org/journal/jmmce)

TL Glow Curve Study, Kinetics, PL and XRD Analysis of

Mn2+ Doped CaAl2O4 Phosphors

Jagjeet Kaur, Nemana Subramanyam Suryanarayana, Beena Jaykumar*, Vikas Dubey,

Ravi Shrivastava, Huma Nazli Baig

Department of Physics, Vishwanath Yadav Tamaskar Post Graduate Autonomous College, Durg, India

Email: *[email protected]

Received July 16, 2012; revised August 20, 2012; accepted August 29, 2012

ABSTRACT

The present paper reports Thermoluminescence (TL) Glow curve of Mn2+ doped CaAl2O4 phosphor with different UV

exposure time. The Glow peak shows general order kinetics and evaluation of kinetic parameters was done by peak

shape method. Calculations of Trap Depth were done with Chen’s different methods and order of kinetics, activation

energy and frequency factor are calculated. The recorded glow curve shifts towards higher temperature with increasing

intensity as a function of UV exposure time until 30 minutes where it is seen that the peak shifts towards low tempera-

ture side and intensity also decreases. The peaks were found at 345˚C, 356.83˚C, 358˚C and 356.73˚C respectively using

the heating rate 6.7˚C/s. The PL (photoluminescence) excitation spectra show peaks at 248 nm and 362 nm whereas

emission spectra shows peaks between 364 nm and 551 nm. Sample was characterized by XRD technique.

Keywords: Phosphors; Photoluminescence; Thermoluminescence; Kinetic Parameters; Trap Depth

1. Introduction

Rare earth and non-rare earth doped inorganic phosphors

are widely used in a variety of applications, such as lamp

industry, radiation dosimetry, X-ray imaging, and color

display [1]. Major applications of the phosphors are in

fluorescent lamps and emission display devices such as

Electroluminescence Panels (EL), Plasma Display Panels

(PDP), Field Emission Displays (FED) and so on [2,3].

This has revived interest in the research on new methods

of phosphor synthesis in recent years. Mn2+ luminescence

can be useful in obtaining a low cost green or red emit-

ting phosphor. Rare earth doped aluminate phosphors are

of special interest, since they show long phosphorescence

and a short-time decay depending on the differing condi-

tions of preparation used [4,5]. In recent years, calcium

aluminates (CaAl2O4) have been the subject of many in-

vestigations primarily due to the fact that this com-

pound has several interesting technological applications.

For example, CaAl2O4 is the main phase in Calcium

Aluminate Cements. Crystalline Calcium Aluminate is

being used in high strength and high toughness cera-

mic—polymer composite materials. For some years, new

application for Calcium Aluminates has emerged in bio-

ceramics, optical-ceramics, catalyst support and struc-

tural ceramics. As a part of our research on phosphor ma-

terials an attempt is made to prepare Mn2+ doped CaAl2O4

phosphor which shows a high TL intensity.

2. Experimental Method

By solid state reaction process, CaCO3, Al2O3, MnCO3

and CaF2 were mixed in stoichiometric ratio by dry grin-

ding in mortar and pestle for nearly 45 minutes. The

mixture is taken in quartz boats and is fired in air at

1300˚C for 1 hour. The sample is then irradiated by UV

radiation 365 nm source. The heating rate used for TL

measurement is 6.7˚C/s. The glow curves were recorded

by using TLD reader I1009 supplied by Nucleonix Sys.

Pvt Ltd. Hyderabad [6,7]. The curves were analyzed by

using computerized glow curve deconvolution program.

The sample was characterized by XRD. The XRD mea-

surements 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 Lynx-

Eye detector). The particle size was calculated using the

Debye-Scherrer formula. The excitation and emission spec-

tra were taken with the help of spectrofluorophotometer.

3. Result and Discussion

3.1. XRD Pattern of CaAl2O4: Mn2+ Doped

Phosphor

*Corresponding author. The XRD pattern of the sample is shown in Fi gure 1,

J. KAUR ET AL.

1082

which confirms that the sample is CaAl2O4: Mn2+ doped

phosphor. It shows the monoclinic structure match with

JCPDS card no. 88-2477. Eleven different peaks are ob-

tained at 2



values of 23.42˚, 27.85˚, 29.8˚, 33.43˚, 35.1˚,

36.73˚, 41.24˚, 46.74˚, 55.27˚, 57.58˚ and 67.22˚. This

shows that the sample have monoclinic structure. The

XRD peaks correspond to Bragg diffraction at (111),

(200), (210), (211), (221/300), (311), (400), (322/410)

and (332) planes of Monoclinic. The sharp peaks indicate

microcrystalline behavior of the CaAl2O4: Mn2+ sample.

Table 1 gives various Bragg reflections that are indexed

using JCPDS Files card 88-2477 and the calculated unit

cell dimensions of CaAl2O4: Mn2+. Inter-planar distance

“d” calculated by Debye-Scherrer formula:

0.9

cos

dβθ



Here



is wavelength of X-ray source, β is FWHM

(Full width half maximum) of XRD pattern and θ is angle

of diffraction. The value of inter-planar distance was found

to be 8.09 nm.

3.2. PL Studies of CaAl2O4: Mn2+ Doped

Phosphor

Figure 2 shows the excitation spectrum having the peak

at 248 nm and 362 nm when given 400 excitation wave-

lengths. Figure 3 shows the emission spectra which has

the peak at 364 nm, 397 nm, 450 nm, 466 nm, 491 nm

and 551 nm when given excitation 254 nm.

3.3. TL Glow Curve and Kinetic Parameter of

CaAl2O4: Mn2+ Doped Phosphor

The kinetic parameters of Mn2+ doped CaAl2O4 phosphor

with different UV exposure time were calculated. The TL

glow curve of Mn2+ doped CaAl2O4 shows general order

kinetics. The UV irradiation of 365 nm is given to the

phosphor. Every time 5 mg of irradiated sample was taken

for TL measurements. Figure 4 shows the comparative

study of TL glow curve of Mn2+ doped CaAl2O4 pho-

sphor as a function of UV exposure time. It is seen that

TL glow curve shifts towards higher temperature with in-

creased intensity, when the irradiation exposure time is

increased. The peak were found at 345˚C, 356.83˚C,

358˚C and 356.73˚C respectively. Table 2 shows the

various parameters like shape factor (µ), activation energy,

and frequency factor of different UV exposure time. Ta-

ble 3 shows the trap depth calculations obtained from

General order kinetics.

20 30 40 50 60 70

1000

2000

3000

4000

5000

6000

Intensity (arb units)

2 Theta

111

200

210

211

221

311 400 322/410

332

Figure 1. XRD pattern of CaAl2O4: Mn 2+doped Phosphor.

Table 1. Indexing of X-Ray Diffraction Pattern (Monoclinic Structure).

Material CaAl2O4

(Calcium Aluminate) Wave Length1.54 FWHM 0.159

Peak 2θ(observed) 2θ(Standard) 2θ(difference) h2 + k2 + l2hkl d spacing

(Observed) (A˚)d spacing

(Calculated) (A˚) Difference

(d spacing) (A ˚)

1 23.42 23.97 –0.55 3 111 8.525 8.516 0.009

2 27.85 27.93 –0.08 4 200 8.450 8.449 0.001

3 29.8 30.06 –0.26 5 210 8.413 8.408 0.005

4 33.43 30.1 3.33 6 211 8.338 8.407 –0.069

5 35.1 35.46 –0.36 7 - 8.301 8.293 0.008

6 36.73 37.21 –0.48 7 - 8.263 8.251 0.012

7 41.24 41.04 0.2 9 221/300 8.148 8.154 –0.005

8 46.74 46.37 0.37 11 311 7.992 8.003 –0.011

9 55.27 54.55 0.72 16 400 7.713 7.738 –0.025

10 57.58 57.43 0.15 17 322/410 7.630 7.635 –0.005

11 67.22 68.27 –1.05 22 332 7.251 7.206 0.044

J. KAUR ET AL. 1083

200 220 240 260 280 300 320 340 360 380400

Intesity (arb units)

Wavelength (nm)

CaAl

2O4: Mn

248nm

362nm

Figure 2. PL excitation spectra of Mn2+ doped CaAl2O4 phosphor with 400 nm excitation.

350 400 450 500 550 600 650

Intensit y (a rb unit s )

wa v e le n g th (n m)

CaAl2O4: Mn

364nm

397nm

466nm

450

551

494

Figure 3. PL emission spectra of Mn2+ doped CaAl2O4 phosphor with 254 nm excitation.

200 300 400 500

500

1000

1500

2000

2500

3000

3500

Inten sity (arb units)

Tem perature 0C

15 m in UV

20 m in UV

25 m in UV

30 m in UV

358

356

345

356

Figure 4. Comparative study of TL glow curve of CaAl2O4 Mn2+ doped with different UV exposure time.

J. KAUR ET AL.

1084

Table 2. Evaluation of kinetic parameters such as activation energy (E), frequency factor S and shape factor (µ) CaAl2O4:

Mn2+ doped phosphor.

UV in min T1(˚C) Tm(˚C) T2(˚C)







µ =





Activation energy

E in (eV)

Frequency factor S in

sec–1

15 309.5 345.6 379.02 36.12 33.4 69.52 0.48 1.36 1.60 × 1012

20 323 356.8 387.76 33.8 30.93 64.73 0.47 1.51 1.65 × 1013

25 322.3 358.1 392.57 35.82 34.46 70.28 0.49 1.43 3.60 × 1012

30 323 356.7 387.09 33.77 30.36 64.13 0.47 1.51 1.65 × 1013

Table 3. Calculation of Trap Depth using Chen’s different

Methods.

Methods 15 min

UV 20 min

UV 25 min

UV 30 min



Ecb kT

















1.35 1.36 1.45 1.49



Ec bkT

 













1.39 1.40 1.48 1.51



Ec bkT

 









 1.40 1.43 1.49 1.52

4. Conclusion

It has been concluded that the Mn2+ doped CaAl2O4

phosphor is monoclinic in structure, with light emitting

in blue-green region of electromagnetic spectrum. The

value of inter-planar distance was found to be 8.09 nm.

The activation energy was calculated to be in the range

of 1.36 to 1.51 eV for different UV exposure time. The

frequency factor was found to be 1.60 × 1012 to 1.65 ×

1013 sec–1.

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