НЕОРГАНИЧЕСКИЕ МАТЕРИАЛЫ, 2008, том 44, № 5, с. 598-600
УДК 535.215.4
The Photoluminescence of Pb2+ Doped CaAl2B2O7 Prepared by Combustion Synthesis
© 2008 Y. PekgozlU*, S. Seyyidoglu**
*Marmara University, Faculty of Art & Science, Department of Chemistry, Istanbul, Turkey **Middle East Technical University, Faculty of Art & Science, Department of Chemistry, Ankara, Turkey
e-mail: pekgozluilhan@yahoo.com Received 01.04.2007
Pb2+ doped CaAl2B2O7 was prepared by a solution combustion synthesis method. The phase of the synthesized material was determined using powder X-ray Diffraction. The photoluminescence properties of Pb2+ doped CaAl2B2O7 material were investigated using a spectrofluorometer. The emission and excitation bands of the Pb2+ doped CaAl2B2O7 material were observed at 352 and 262 nm, respectively. The Stokes shift of the synthesized material was calculated to be 9759 cm1.
INTRODUCTION
Combustion synthesis has been widely applied to prepare phosphors recently. This synthesis technique makes use of the heat energy generated by the redox exothermic reaction at low igniting temperature (~500°C) between oxidizers (metal nitrates) and reducers (organic fuels as urea, carbohydrazide, glycine, citric acid and malonic acid etc.). Moreover, this process is safe, simple, cheap and energy saving, compared with conventional techniques [1].
The photoluminescence properties of the Pb2+ ion in inorganic borates have been the subject of investigation for many years [2-7]. It is well known that the photoluminescence properties of the Pb2+ ion depend strongly on the nature of the host lattice and temperature.
Aluminum borates have been the subject of much research interest during the past decade because of their potential applications as luminescence hosts [8-15]. CaAl2B2O7 is characterized by an association of BO3 triangles, CaO6 octahedra and AlO4 tetrahedra. The crystal structure of CaAl2B2O7 has been reported in detail elsewhere [16]. Although the photoluminescence properties of Ce3+, Gd3+, Tb3+, Eu2+ doped CaAl2B2O7 have been studied in detail [12, 13], the photoluminescence properties of Pb2+ doped CaAl2B2O7 were not reported until recently.
In this work, Pb2+ doped CaAl2B2O7 was prepared by a solution combustion method. After synthesis and characterization, the photoluminescence of CaAl2B2O7: Pb2+ (0.01 mol) was studied using a spectrofluorometer.
EXPERIMENTAL
Cax _ xPbxAl2B2O7 (x = 0.01) was prepared by a solution combustion synthesis method followed by heating of the precursor combustion ash at 1000°C in air. Stoichiometric amounts of Al(NO3)3 ■ 9H2O, Ca(NO3)2,
H3BO3 and Pb(NO3)2 were dissolved in a minimum amount of distilled water and placed in a porcelain container. Pb2+(x) in Cax _ xAl2B2O7 is 0.01. Urea was added to the well-mixed mixture. The precursor solution was introduced into a muffle furnace (Lenton LTF 1500) and maintained at 500°C for 10 min. The product powder was removed from furnace.
This voluminous and foamy combustion ash was easily milled to obtain a precursor powder of CaAl2B2O7: Pb2+. The well-mixed powder was pressed into a pellet, which was then placed in an alumina crucible and heated in a muffle furnace (Lenton LTF 1500) for 4 h at 1000°C in air.
XRD structural analysis of the product was performed on an X-ray Rigaku Diffractometer Miniflex with Cu^a (30 kV, 15 mA, X = 1.54051 A) radiation at room temperature. Scanning was generally performed between 5 and 60 degree 20. Measurement was made with 0.05° steps and a 1°/min scan rate. The divergence slit was variable, and the scattering and receiving slits were 4.2° and 0.3 mm, respectively.
Photoluminescence excitation and emission spectra were measured at room temperature with a Varian Cary Eclipse spectrofluorometer equipped with a 15 W Xenon pulse lamp.
RESULTS AND DISCUSSION
The XRD pattern of Pb2+ doped CaAl2B2O7 material is shown in Fig. 1. The XRD pattern is in agreement with the standard monoclinic P-CaAl2B2O7 (JCPDS Card No: 19-0206).
The luminescence of Pb2+ in host materials can be described by the 1S0 —- 3P01 transition which originates from (6s)2 - (6s)1(6p)2 transition. Typically at room temperature, emission is observed from the P —- 1S0 transition, at low temperatures the highly forbidden 3P0 —► 1S0 emission is also observed [5].
THE PHOTOLUMINESCENCE OF Pb2+ DOPED CaAl2B207
599
Intensity, a.u. 4000
3500 3000 2500 2000 1500 1000 500 0
5 10 15 20 25 30 35 40 45 50 55 60
26, deg
Fig. 1. XRD pattern obtained for CaAl2B2O7: Pb2+(0.01 mol) prepared by a solution combustion synthesis method.
As seen in Fig. 2, the excitation band of the synthesized material CaAl2B2O7: Pb2+ (0.01mol) was observed at 262 nm which is assigned to the 1S0 —► 3P1 transition. The maximum emission band was observed at 352 nm corresponding to the 3P1 excited state level to the 1S0 ground state transition upon excitation with at 262 nm. The emission band of the synthesized material lies between 300 nm to 450 nm. We observed no splitting or multiple bands in the excitation and emission spectra. Although the emission band of Pb2+ shows neither multiple bands nor splitting, we believe that the Pb2+
Intensity, a.u. 250
200
150
100
50
200
250
300
350
400 450 500 Wavelength, nm
,2+
Fig. 2. Photoluminescence spectra of CaAl2B2O7: Pb (0.01 mol) at room temperature. The excitation spectra were recorded at the maxima of the corresponding emission band (352 nm) and the emission spectrum was plotted at room temperature when excited at 262 nm.
ions incorporate into only one site in the crystal lattices. Thus, Pb2+ here is supposed to occupy the Ca2+ sites (1.00 A) and not Al3+ sites (0.39 A) due to the size of ions.
The Stokes shift of the synthesized material was calculated to be 9759 cm-1 using the excitation band at 262 nm and the emission band at 352 nm.
CONCLUSION
Pb2+ doped CaAl2B2O7 material was prepared by a solution combustion synthesis method. The phase of the synthesized material was determined using powder X-Ray Diffraction. The XRD pattern of the synthesized material is in agreement with the standard monoclinic |3-CaAl2B2O7. The photoluminescence properties of the Pb2+ doped CaAl2B2O7 material were investigated using a spectrofluorometer. The maximum emission band was observed at 352 nm from the 3P1 —► 1S0 transition upon excitation with 262 nm radiation at room temperature. The Stokes shift of the synthesized material CaAl2B2O7: Pb2+ was calculated as 9759 cm-1.
Based on the above observations, Pb2+ doped CaAl2B2O7 emits in the UV region. Therefore, we believe that it can potentially be used as a UV phosphor.
The authors are grateful to Sulin Tapcy odlu and Michael W. Pitcher for their support.
1.
2.
REFERENCES
Peng T., Yang H, Pu X. et al. Combustion Synthesis and Photoluminescence of SrAl2O4: Eu, Dy Phosphor Nano-particles // Mater. Lett. 2004. V. 58. No 3-4. P. 352-356.
Folkerts H.F., Blasse G. Luminescence of Pb2+ in SrTiO3 // Chem. Mater. 1994. V. 6. P. 969-972.
НЕОРГАНИЧЕСКИЕ МАТЕРИАЛЫ том 44 № 5
2008
600
PEKGÖZLÜ ë flp.
3. Yen W.M., Weber M.J. Inorganic Phosphors. CRC Press, 2004. P. 146-160.
4. Sankar R, Rao G VS. Luminescence Studies on Doped Borates // J. Alloys Compd. 1998. V. 281. P. 126-136.
5. Folkerts H F, Blasse G. Luminescence of Pb2+ in Several Calcium Borates // J. Mater. Chem. 1995. V. 5. No 2. P. 273-276.
6. Leskela M, Koskentalo T, Blasse G. Luminescence Properties of Eu2+, Sn2+, Pb2+ in SrB6O10 and Sr1 - ;[MnxB6O10 // J. Solid State Chem. 1985. V. 59. P. 272-279.
7. Meijerink A., Jetten H, Blasse G. Luminescence and Energy Transfer in Lead-Activated Strontium Haloborate // J. Solid State Chem. 1988. V. 76. P. 115-123.
8. Benitez J.S., Andres A., Marchal M. et al. Optical Study of SrAl17B03O4: Eu, R (R = Nd, Dy) Pigments with Long-Lasting Phosphorescence for Industrial Uses // J. Solid State Chem. 2003. V. 171. No 1-2 P. 273-279.
9. Kutty T.R.N. Luminescence of Doped Aluminoborates // Mater. Res. Bull. 1990. V. 25. P. 343-348.
10. Jagannathan R, Rao R.P., Kutty T.R.N. Eu2+ Luminescence in MAl3BO7 Aluminoborates // Mater. Res. Bull. 1992. V. 27. P. 459-466.
11. You H, Hong G. The Change of Eu3+-Surroundings in The System Al2O3-B2O3 Containing Eu3+ Ions // J. Phys. Chem. Solids. 1999. V. 60. No 3. P. 325-329.
12. You H, Hong G. Luminescence and Energy Transfer Phenomena of Several Rare Earth Ions in the CaAl2B2O7 // Mater. Res. Bull. 1997. V. 32. No 6. P. 785-790.
13. Chang K.S. A Fundamental Study of Eu2+ Luminescence in Aluminum Borate Compounds // J. Korean Chem. Soc. 2000. V. 44. No 4. P. 350-355.
14. Lucas F, Jaulmes S, Quarton M. et al. Crystal Structure of SrAl2B2O7 and Eu2+ Luminescence // J. Solid State Chem. 2000. V. 150. P. 404-409.
15. Tian L, Yu B.Y, Pyun CH. et al. New Red Phosphors BaZr(BO3)2 and SrAl2B2O7 Doped with Eu3+ for PDP Applications // Solid State Commun. 2004. V. 129. No 1. P. 43-46.
16. Chang K.S, Keszler D A. CaAl2(BO3)2O: Crystal Structure // Mater. Res. Bull. 1998. V. 33. No 2. P. 299-304.
HEOPÉAHH^ECKHE MATEPHAHbl tom 44 < 5 2008
Для дальнейшего прочтения статьи необходимо приобрести полный текст. Статьи высылаются в формате PDF на указанную при оплате почту. Время доставки составляет менее 10 минут. Стоимость одной статьи — 150 рублей.