Combustion synthesized tetragonal Y2O3:Gd3+ nanophosphors: Structural and photoluminescence studies

Combustion synthesized tetragonal Y2O3:Gd3+ nanophosphors: Structural and photoluminescence studies

Accepted Manuscript Title: Combustion Synthesized Tetragonal Y2 O3 :Gd3+ Nanophosphors: Structural and Photoluminescence Studies Authors: Raunak kumar...

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Accepted Manuscript Title: Combustion Synthesized Tetragonal Y2 O3 :Gd3+ Nanophosphors: Structural and Photoluminescence Studies Authors: Raunak kumar Tamrakar, Kanchan Upadhyay PII: DOI: Reference:

S0030-4026(17)30711-8 http://dx.doi.org/doi:10.1016/j.ijleo.2017.06.042 IJLEO 59305

To appear in: Received date: Accepted date:

15-3-2017 13-6-2017

Please cite this article as: Raunak kumar Tamrakar, Kanchan Upadhyay, Combustion Synthesized Tetragonal Y2O3:Gd3+ Nanophosphors: Structural and Photoluminescence Studies, Optik - International Journal for Light and Electron Opticshttp://dx.doi.org/10.1016/j.ijleo.2017.06.042 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Combustion Synthesized Tetragonal Y2O3:Gd3+ Nanophosphors: Structural and Photoluminescence Studies Raunak kumar Tamrakara* and Kanchan Upadhyayb aDepartment

of Applied Physics, Bhilai Institute of Technology (Seth Blakrishan memorial), Durg, (C.G.), 491001, India

bDepartment

of Chemistry, Shri Shankaracharya Vidyalaya, Hudco, Bhiali (C.G.), India

*Corresponding Author Email ID:[email protected] Abstract The photoluminescent Gd3+ doped Y2O3 nanoparticle has been synthesized by a solution combustion synthesis process. X-ray diffraction (XRD) and Field Emission Gun Scanning electron microscopy (FEG-SEM) were used to determine the structure and morphology of the nanophosphor. Photoluminescent spectroscopy (PL) was used to analyse luminescence properties of the prepared phosphor. The emission spectra have peaks centred at 314 nm in UV region and 614 and 580 nm. The process of emission mechanism is also discussed. Keywords: Y2O3:Gd3+. Photoluminescence, XRD, Introduction:Assimilation of rare earth ion with wide band gap host material enhances optical and magnetic behaviour of the material [1,2]. Gd3+ ion has attracted researchers due to its scintillation properties and optical behaviour [3-5]. Gd3+ ion has more hole conductivity due to its 4f state [6]. Development of lasers in near ultraviolet region made Gd3+ ion an important dopant material. All the transitions in Gd3+ ion takes place in near UV region due to resonant excitation of the Gd3+ level [7]. It also give rise to resonant multi photon process 1

which are generally investigated for rare earth ions such as Er3+, Tb3+, Tm3+ Nd3+ etc. [8-11]. The phosphor shows down conversion phenomenon, in which one excitation photon converted into two photon of lower energy. In Two photon emission process an electronic transition is accompanied by simultaneous emission of a photon pair. The transition energy as a whole remains conserved during emission but individual photons may associate with different energies [12]. Rare earth compounds are widely used as luminescence materials. They are excellent host lattice for luminescent materials [13-15]. Y2O3 is one of the best host materials for down as well as up conversion process due to its unique physical properties such as chemical durability, thermal stability, optical properties and low phonon energy [16-18]. Previously various methods have been used to synthesize different Y2O3 phosphors, the synthesis method includes micro emulsion [19], spray pyrolysis method [20], precipitation method [21], combustion method [22,23], sol-gel method [24] etc. Here we have synthesized the uniform cubic Gd3+ doped Y2O3 phosphor by solution combustion method using urea as fuel followed by heat treatment. The structure of the prepared phosphor was confirmed by XRD and FEG-SEM analysis techniques. Optical properties were studied under 275 nm excitation and emission was observed in UV as well as visible regions. The mechanism of emission process has also been discussed. Synthesis:Yettrium nitrate Y(NO3)3.6H2O, Gd(NO3)3.6H2O was used as precursor material. The combustion process was assisted by using urea as a fuel. All the precursors in stoichiometric amount were mixed together and dissolved in small amount of water and transferred into an alumina crucible. The crucible was then introduced into a preheated muffle furnace

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maintained at 500±10°C. inside the furnace the mixture present in crucible under goes spontaneous combustion by removal of gases like NO2, CO2 and H2O [25]. Results and discussion Structural analysis:The XRD pattern of the prepared Y2O3:Gd3+ phosphor is presented in figure 1. The XRD pattern well matched with the JCPDS card no 83-0927 and confirms the presence of cubic phase of Y2O3 without any impurity peak. The average crystal size was found around 8 nm, calculated by using Scherer’s formula [26]. The morphology and chemical composition of the phosphor was examined by using SEM and EDX analysis. SEM image of the phosphor is presented in figure 2. It represents agglomeration in the phosphor. The EDX spectra have Y, O and Gd. The peak of Gd represents the doping of Gd3+ ion (Fig 3) Figure1: XRD pattern of Y2O3:Gd3+ is here Figure 2. SEM image of Y2O3:Gd3+ phosphor is here Figure 3: EDX spectra of Y2O3:Gd3+ is here Photoluminescence studies:For photoluminescence study of the phosphor excitation and emission spectra were recorded. The excitation spectrum has intense peak at 275 nm and weak peaks at 255nm and 249 nm (Fig 4). Excitation peak at 275 nm is intense one so emission spectra were recorded under 275 nm excitation. The emission spectra has peaks centred at UV region at 314 nm along with weak emissions at 317 nm, 395 nm and few emission peaks in visible regions were also observed centred at 580 nm and 614 nm (Fig 5). The observed excitation and emission depends on the transition between the energy levels of Gd3+ ion.

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S7/2 level absorbed one

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275 nm photon and excites to 6Ij level. This excited state under goes radiatively and non radiatively transition. 6Ij level non-radiatively populates 6Pj level, transition from 6Pj to 8S7/2 is responsible for emission peak at 315 nm [27]. Visible emission at 614 nm and 580 nm is due to two photon emission from 6Ij level to 8S7/2 level. 8S7/2 absorbs 275 nm wave length corresponding to the 4.5ev energy and emits two photons of 2.13 eV and 2.02 eV energy which corresponds to the 580 nm and 614 nm wave lengths respectively [12].

Figure 4. Excitation spectra of Y2O3:Gd3+ phosphor is here Figure 5. Emission spectra of Y2O3:Gd3+ is here Figure 6. Energy level transition for emission peaks in Y2O3:Gd3+ is here Emission spectra of Y2O3:Gd3+ phosphor was recorded for different samples i.e. fresh, annealed at 600 and 900°C to observe the effect of annealing on emission spectra. Figure 7 shows the spectra under different annealing temperatures. It can be clearly seen from the figure that the annealing temperature does not affect the peak positions. Intensity of emission increases with increasing annealing temperature. To study the effect of Gd3+ concentration emission spectra was recorded for different concentration of Gd3+ ion from 0.5 mol% to 2 mol%. The peak position remains unaffected from Gd3+ concentration it only affects the intensity of emission peaks. Intensity of emission peaks increases up to 1.5 mol % Gd3+ ion after this concentration a decrease in intensity is observed. The initial increase in intensity is due to decrease in inter ionic distances between Gd3+ ion which promotes energy transfer from between two nearby Gd3+ ion. After a certain concentration of Gd3+ ion further decrease in inter-ionic distance results in concentration quenching. Figure 7. Effect of annealing on emission spectra of Y2O3;Gd3+ phosphor is here 4

Figure 8. Effect of Gd3+ ion on emission spectra of Y2O3:Gd3+ phosphor is here

Conclusion:Cubic Y2O3:Gd3+ was synthesized by solution combustion synthesis method. The structure of prepared phosphor was determined by XRD and SEM analysis. The crystal size was obtained around 8 nm for freshly prepared phosphor. The emission spectra were recorded under 275 nm excitation. The emission spectra have peaks at UV region at 314 nm and in visible region at 614 nm and 580 nm. The visible emission by Gd3+ ion may be due to two photon processes. References: 1. S. Dhar, O. Brandt, M. Ramsteiner, V.F. Sapega, K.H. Ploog, Phys. Rev. Lett. 94, (2005) 037205. 2. S. Dhar, L. Perez, O. Brandt, A. Trampert, A.H. Ploog, Phys. Rev. B 72 (2005) 245203. 3. P.D. Cozzoli, M.L. Curri, A. Agostiano, J. Phys. Chem. B 107 (2003) 4756. 4. R. Xie, Appl. Phys. Lett. 88 (2006) 134103. 5. Fu, M. Kobayashi, J.M. Parker, J. Luminesc. 94 (2001) 321. 6. L. Liu, P.Y. Yu, Z. Ma, S.S. Mao, Phys. Rev. Lett. 100 (2008) 127203. 7. J. Sytsma, G.F. Imbusch and G. Blasse, J. Chem. Phys. 9 1 (1989) 1456; J. Chem. Phys. 92 (1990) 3249 (E). 8. R. Raue, K. Nieuwesteeg and W. Busselt, J. Luminescence 48/49(1991)485. 9. M. Dulick, G.E. Faulkner, N.J. Cockroft and D.C. Nguyen, J. Luminescence 48/49 (1991) 517. 10. N. Pelletier-Allard and R. Pelletier, J. Luminescence 48/49 (1991) 867.

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11. A.J. Silversmith, W. Lenth and R.M. Macfarlane, Appl. Phys. Letters 51 (1987) 1977 12. Hayat, A.; Ginzburg, P.; Orenstein, M. (2008). "Observation of Two-Photon Emission from Semiconductors". Nature Photon. 2 (4): 238. 13. Y.B. Mao, T. Tran, X. Guo, J.Y. Huang, C.K. Shih, K.L. Wang, J.P. Chang, Adv. Funct. Mater. 19 (2009) 748. 14. G. Jia, M. Yang, Y.H. Song, H.P. You, H.J. Zhang, Cryst. Growth Des. 9 (2009) 301. 15. G. Jia, Y.H. Zheng, K. Liu, Y.H. Song, H.P. You, H.J. Zhang, J. Phys. Chem. C 113 (2009) 153. 16. M.K. Devaraju, S. Yin, T. Sato, Cryst. Growth Des. 9 (2009) 2944. 17. L. Xiong, T. Yang, Y. Yang, C. Xu, F. Li, Biomaterials 31 (2010) 7078. 18. Q. Lü, Y. Wu, L. Ding, G. Zu, A. Li, Y. Zhao, H. Cui, J. Alloys Compd. 496 (2010) 488. 19. Q. Pang, J. Shi, Y. Liu, Mater. Sci. Eng. B 103 (2003) 57. 20. L. Wang, Y. Zhou, Z. Quan, J. Lin, Mater. Lett. 59 (2005) 1130. 21. B. Alken, W.P. Hsu, E. Matijevic, J. Am. Ceram. Soc. 71 (1988) 845. 22. Z.M. Qi, C. Shi, Appl. Phys. Lett. 81 (2002) 2857. 23. H. Song, B. Chen, Appl. Phys. Lett. 81 (2002) 1776. 24. M. Pang, J. Lin, Z. Cheng, Mater. Sci. Eng. B 100 (2003) 124. 25. Raunak Kumar Tamrakar, D. P. Bisen and Kanchan Upadhyay, Effect of annealing on down-conversion

properties

of

monoclinic

Gd2O3:Er3+

nanophosphors,

Luminescence 2015; 30: 812–817 26. Tamrakar RK, Bisen DP, Robinson CS, Sahu IP, Brahme N. ytterbium doped gadolinium oxide (Gd2O3:Yb3+) phosphor: topology, morphology, and luminescence behaviour. Indian J Mater Sci 2014. DOI: 10.1155/2014/396147. 27. R.T Wegh, et al. Phys. Rev. B 56, 13841 (1997).

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Y2O3:Gd

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Figure1: XRD pattern of Y2O3:Gd3+

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Figure 2. SEM image of Y2O3:Gd3+ phosphor

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Figure 3: EDX spectra of Y2O3:Gd3+

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Figure 5. Emission spectra of Y2O3:Gd3+

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Figure 6. Energy level transition for emission peaks in Y2O3:Gd3+ 12

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Figure 7. Effect of annealing on emission spectra of Y2O3;Gd3+ phosphor

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Figure 8. Effect of Gd3+ ion on emission spectra of Y2O3:Gd3+ phosphor

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