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Combustion synthesis of Sr2B2O5:Tb3+ green emitting phosphor for solid state lighting
Optik 127 (2016) 1603–1606
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.de/ijleo
Combustion synthesis of Sr2 B2 O5 :Tb3+ green emitting phosphor for solid state lighting V.R. Panse a , N.S. Kokode b , A.N. Yerpude c,∗ , S.J. Dhoble d a
Department of Applied Physics, NCET Gondwana University, Gadchiroli 442605, India N.H. College, Bramhapuri, Dist-Chandrapur 441206, India Department of Physics, N.H. College, Bramhapuri, Dist-Chandrapur 441206, India d Department of Physics, RTM Nagpur University, Nagpur 440033, India b c
a r t i c l e
i n f o
Article history: Received 2 April 2015 Accepted 9 November 2015 Keywords: Phosphor Borates XRD SEM FTIR
a b s t r a c t Terbium doped Sr2 B2 O5 green phosphor was synthesized by combustion synthesis method at about 550 ◦ C. Further, analyzed by XRD technique and XRD pattern of prepared phosphor is well match with standard JCPDs file. The morphology and structure of the phosphor were characterized by scanning electron microscopy. The chromatic coordinates estimated from emission spectra shown by CIE chromatic diagram and values observed are Cx = 0.263, Cy = 0.723. The vibrational characteristics were studied with the help of FTIR. The excitation and emission spectra specify that the prepared phosphor can be effectively excited by 353 nm and reveal bright green emission centered at 545 nm consequent to the D → F transition of Tb3+ ion. From the obtained results it is concluded that present phosphor may be efficient photoluminescent materials for solid-state lighting and energy saving applications. © 2015 Elsevier GmbH. All rights reserved.
1. Introduction Now a day’s use of tri-color (RGB) phosphor has paying more and more attention has been paid to the preparation of high-efficiency, high chemical stability and low thermal quenching blue, green and red phosphors suitable for energy saving applications [1,2]. White light emitting diodes (w-LEDs) have many advantages, e.g. long lifetime, high luminescence efficiency, high brightness, low energy consumption and environmental-friendliness, they are the most important source and a very bright future in various lighting applications because of their high energy efficiency and cost effectiveness compared to incandescent bulbs. Rare-earth luminescent materials have been widely applied in many fields, such as color television sets, picture tubes, computer monitors, solid state lighting, due to their abundant 4f energy levels of rare-earth ions and their transition properties, Researches on phosphors, particularly, rare earth phosphors for white LED are extremely active [3]. In practically phosphors were paying more and more attention mainly on various oxygen containing inorganic compounds, such as borates, aluminates, silicates, oxides and aluminoborates. Materials based on borate are very helpful classes of hosts material for luminescence because of their high UV transparency and exceptional optical damage threshold [4]. Borates based inorganic
phosphors have paying much attention owing to their low synthesis temperature, high stability, and superior transparency in the UV region [5]. Luminescence properties of the trivalent rare earth activated compounds have received great concentration in the area of solid state lighting as well as white light emitting diode [6,7]. Owing to advantages of white light-emitting diode (LED) such as environmental protection, long lifetime, and low energy consumption is considered as the next generation solid-state light sources for substituting the usually used fluorescent lamps and, incandescent lamps [8–10]. As a host borate compounds played a very important role for the development of luminescent materials [11,14]. As phosphor materials for a several applications [12,13] various borate materials used as a host and doped with rare earth ions and other ions have been reported earlier by various groups [15,16]. We have prepared a borate based green color emitting phosphor activated with trivalent terbium ion for their possible application for energy consumption and solid-state lighting and characterized by X-ray diffraction (XRD), Scanning electron microscopy, photoluminescence spectra, Fourier transform infrared (FT-IR) spectra, chromaticity nature of Sr2 B2 O5 :Tb3+ phosphors. 2. Experimental 2.1. Materials
∗ Corresponding author. Tel.: +91 9637782611. E-mail address: [email protected] (A.N. Yerpude). http://dx.doi.org/10.1016/j.ijleo.2015.11.030 0030-4026/© 2015 Elsevier GmbH. All rights reserved.
In this work, we prepared Sr2 B2 O5 phosphor doped with trivalent terbium ion by using a combustion synthesis method with
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extra heat treatment. Here we used SrNO3 (A.R.) (99.999%), H3 BO3 (A.R.) (99.999%) and NH2 CONH2 (A.R.) (99.999%), from Merck as raw materials to prepare the phosphor material with and without dopant and Tb4 O7 which was added as an activator or called as dopant respectively.
2.2. Preparation of Sr2 B2 O5 :Tb3+ phosphor To synthesize Sr2 B2 O5 :Tb3+ phosphor, chemical compound such as SrNO3 (A.R.) (99.999%), H3 BO3 (A.R.) (99.999%) and NH2 CONH2 (A.R.) (99.999%), from Merck in the stoichiometric ratio were mixed in an agate mortar by adding up an amount of urea as a fuel and then grinded for minimum time duration of 20–30 min each concentration separately. Finally, the mixture was placed into a porcelain crucible and then using vertical furnace, fired at 550 ◦ C in an air atmosphere for very short time duration. After firing, the samples take out from the furnace and then cooled slowly it at room temperature. The product of heated phosphor material obtained was crushed again in an agate mortar, for time duration of 45–60 min each, after that the crushed sample is again fired at 600 ◦ C for 12 h duration in an air atmosphere. After completing heating process the sample slowly cooled and then kept it outside from the furnace. The product of prepared phosphor material obtained was crushed in agate mortar to convert it into fine particle for obtaining fine powder sample.
2.3. Characterization The phase structure of samples obtained in the powder form was confirmed by taking the X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectrometry (IR) studies. The photoluminescence (PL) emission spectra of the samples were recorded using a fluorescence spectrometer (Shimadzu, RF 5301 PC). The photoluminescence spectra, i.e. emission and excitation were recorded using a spectral slit width of 1.5 nm. All the above data were measured and recorded at room temperature. The chromaticity nature is studied with the help of CIE software.
3. Results and discussion 3.1. XRD measurement According to Lin, Cheng et al.’s work [17] and Jiayue Sun et al.’s work [18] the crystal structure of Sr2 B2 O5 phase is belongs to monoclinic crystal structure with a space group of P21/c and the lattice ˚ b = 5.341(1) A, ˚ constants of monoclinic Sr2 B2 O5 are: a = 7.719 (4) A, c = 11.873(2) A˚ and Z = 4. It is well established fact that every crystalline material gives a unique x-ray diffraction pattern. A careful study of diffraction patterns of unknown materials offers a powerful means of qualitative identification of various phases present therein. It is therefore proved to be a quick and non destructive method for an identification of compounds. In addition to this the information obtained on lattice parameters using the x-ray powder diffraction data, gives better insight to structural changes produced in compound by physical or chemical process. These merits put this technique above all, which are, in general, used for structural characterization of material. The XRD pattern of Sr2 B2 O5 along with JCPDS file is shown in Fig. 1, is well match linking the as prepared phosphor material and the JCPDS data (73-1930) was observed. 3.2. SEM micrograph of Sr2 B2 O5 phosphor Fig. 2 shows the SEM micrographs of the combustion synthesized Sr2 B2 O5 phosphor. The images of prepared Sr2 B2 O5 phosphors show the crystallites with agglomerated condition. From Fig. 2 it is clear that crystallite size of the prepared phosphor within the range of micrometer. Owing to growth of huge amount of gases a well expected dense flake foam and rod like morphology is observed. It is clear that the approximate size of the particles might be in micrometer range which is in favor of its application in solid state lighting. Due to their ability of high luminescence with the advantage of micrometer dimension, suggest that this phosphor will find further applications in display and lighting field [19]. 3.3. Photoluminescence properties of Sr2 B2 O5 :Tb3+ phosphor In order to find out whichever prospective uses of the trivalent terbium ions doped with Sr2 B2 O5 phosphors, we have to
Fig. 1. XRD pattern of Sr2 B2 O5 phosphor.
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Fig. 4. Emission spectrum of Sr2 B2 O5 :Tb3+ phosphor.
Fig. 2. SEM images of Sr2 B2 O5 phosphor.
recognize their photoluminescence spectra, i.e. emission and excitation which was recorded from room temperature to relative temperature. Lots of phosphors which reveal feature of green emission of 5 D4 → 7 F5 transition trivalent terbium ions can be extensively used as luminescent centers [20,21]. The Tb3+ ions used as an activator of green emitting luminescent materials consist of major emission lines peaking at around 422 nm, 439 nm, 463 nm, 491 nm, 545 nm, 588 nm and 625 nm, which are due to the distinctive 5 D3 → 7 F5 , 5 D3 → 7 F4 , 5 D3 → 7 F3 , 5 D4 → 7 F6 , 5 D4 → 7 F5 , 5 D → 7 F and 5 D → 7 F transitions of trivalent terbium ions 4 4 4 3 correspondingly. The photoluminescence emission and excitation measurements are taken at air atmosphere. As shown in Fig. 3, excitation spectrum of Sr2 B2 O5 :Tb3+ phosphor observed at 545 nm emission wavelength consisting of a broad band as well as some sharp lines. The broad band is due to f-d interaction while sharp lines are due to f–f transitions. The emission spectrum as shown in Fig. 4 has sharp lines on account of f–f transition of Tb3+ ions. The emission spectrum usually has major contribution from 5 D4 → FJ (J = 6, 5, 4, 3) but a weak peak around due to 5 D3 → 7 FJ (J = 6, 5,
Fig. 3. Excitation spectrum of Sr2 B2 O5 :Tb3+ phosphor.
4, 3) can also be seen. By the selection rule J = ±1 for electric dipole and J = 0, ±2 for magnetic dipole transitions respectively, the nature of 5 D4 → 7 FJ transitions is governed. The most extreme luminescence emission, i.e. green emission of prepared phosphor observed at 545 nm (5 D4 –7 F5 ), under the excitation of 353 nm. As shown in Fig. 4, the emission intensity of 5 D3 level is very weak and but further increasing with increasing Tb3+ concentration, followed by the enhancement of the emission from the 5 D4 level. As the concentration of Tb3+ is changed, the cross-relaxation effect becomes stronger, which enhances the intensity of green emission at 545 nm. The reason that has been assigned to weak luminescence from 5 D3 level is due to the lack of phonon energy of the host. The smaller the phonon energy of the host at diluted concentrations of terbium ions, the lower will be the 5 D3 emission intensity and vice versa [22,23]. From the emission and excitation of the prepared phosphor we concluded that this become the green emitting phosphor for solid state lighting. The emission observed for the excitation is conclude that the prepared phosphor material become the phosphor material used for solid state lighting having low energy consumption. 4. Fourier transform infrared (FT-IR) of Sr2 B2 O5 phosphors In order to study the molecular and structural environment of the entitled phosphor FTIR spectrum in the range 4600–400 cm−1 was recorded at room temperature by a bruker spectrometer with 40 scans and the resolution of 4.0 cm−1 . A distinctive FTIR spectrum, i.e. Fourier transform infrared radiation, the obtained infrared spectroscopy of combustion synthesized Sr2 B2 O5 phosphor is shown in Fig. 5. In infrared spectroscopy, IR radiation is accepted through a sample prepared. Some of infrared radiation is passed through (transmitted) the sample and some of it is absorbed by the sample. The considerable spectrum of prepared sample represents the
Fig. 5. FTIR spectra of Sr2 B2 O5 phosphors.
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molecular transmission and absorption creating a fingerprint of the sample. As like a fingerprint no two unique molecular structures produce the same infrared spectrum. These terms makes infrared spectroscopy helpful for several types of analysis used for different studies [24]. The B O bond which indicates stretching vibration in [BO3 ] units due to varied groups at 1450 cm−1 . Bending vibrations of H O H band which are due to crystal water included in compound is slightly seen at 1376 cm−1 . The presence of the band at 1150 cm−1 assigned to asymmetric stretching vibrations of trihedral (BO3 ) borate groups. The peak observed at 732 cm−1 , 680 cm−1 wavelength indicates in plane bending vibrations of trihedral (BO3 ) groups. It can classify unidentified materials, also used to determine the excellence or consistency of a prepared sample. It can find out the amount of components in a mixture. From the spectrum it is observed that the prepared phosphor material, i.e. Sr2 B2 O5 without dopant are characterized by nine bands which is shown in figure, with energies ranging from 625 to 1450 cm−1 such as 1450 cm−1 ; 1376 cm−1 ; 1150 cm−1 ; 1010 cm−1 ; 960 cm−1 ; 810 cm−1 ; 732 cm−1 ; 680 cm−1 ; 625 cm−1 corresponds to the formation of the Sr2 B2 O5 phosphor and areas signed to the characteristic metal–oxygen vibrational modes in its configuration. Rare earth ions in general are known to yield good luminescence when used as dopants in different host matrices. 5. Conclusions Tb3+ doped Sr2 B2 O5 green emitting phosphors successfully prepared by combustion method and well matched with standard JCPDS file. From the PL results obtained it is fulfilled that, Sr2 B2 O5 host is suitable for trivalent terbium emission which is peaking at 545 nm, 422 nm, 439 nm, 463 nm, 545 nm, 588 nm, 625 nm, for the excitation of 353 nm due to 5d–4f transition. The strongest green emission observed at 545 nm due to 5 D4 → 7 F5 transition. Morphology of the phosphors shows the rod like structures having micrometer size. Nature of bonding is studied by Fourier transform infrared spectroscopy. The stokes shift and the frequency for the prepared phosphor is found to be 192 nm and 5.76 × 10−15 m respectively The obtained results shows that the prepared phosphors having possible application as a green emitting phosphor which is suitable for energy consumption and solid state lighting. References [1] A. Lakshmanan, R.S. Bhaskar, P.C. Thomas, R.S. Kumar, V.S. Kumar, M.T. Jose, A red phosphor for nUV LED based on (Y,Gd)BO3 :Eu3+ , Mater. Lett. 64 (2010) 1809–1812.
[2] Y. Liu, Z. Yang, A novel green luminescent material AlPO4 :Tb3+ , Mater. Lett. 65 (2011) 1853–1855. [3] G.M. Cai, F. Zheng, D.Q. Yi, Z.P. Jin, X.L. Chen, New promising phosphors Ba3 InB9 O18 activated by Eu3+ /Tb3+ , J. Lumin. 130 (2010) 910–916. [4] K. Kim, Y. Moon, S. Choi, H. Jung, S. Nahm, Luminescent properties of a novel green-emitting gallium borate phosphor under vacuum ultraviolet excitation, Mater. Lett. 62 (2008) 3925–3927. [5] C.K. Lin, M. Yu, M.L. Pang, J. Lin, Photoluminescent properties of sol–gel derived (La, Gd)MgB5 O10 :Ce3+ /Tb3+ nanocrystalline thin films, Opt. Mater. 28 (2006) 913–918. [6] A.N. Yerpude, S.J. Dhoble, Luminescent properties of Eu2+ and Dy3+ ions in Ba4 Al2 O7 phosphor for solid state lighting, J. Lumin. 132 (2012) 1781–1785. [7] K.N. Shinde, S.J. Dhoble, Luminescence in Dy3+ and Eu3+ activated K3 Al2 (PO4 )3 , J. Fluoresc. 21 (2011) 2053–2056. [8] W.J. Yang, L. Luo, T.M. Chen, N.S. Wang, Luminescence and energy transfer of Euand Mn-coactivated CaAl2 Si2 O8 as a potential phosphor for white-light UVLED, Chem. Mater. 17 (15) (2005) 3883–3888. [9] I.M. Nagpure, V.B. Pawade, S.J. Dhoble, Combustion synthesis of Na2 Sr(PO4 )F:Dy3+ white light emitting phosphor, Luminescence 25 (2010) 9–13. [10] Z. Li, J. Zeng, G. Zhang, Y. Li, A new promising phosphor, Na3 La2 (BO3 )3 :Ln (Ln = Eu, Tb), J. Solid State Chem. 178 (2005) 3624–3630. [11] N.S. Bajaj, S.K. Omanwar, Combustion synthesis and characterization of phosphor KSr4 (BO3 )3 :Dy3+ , Opt. Mater. 35 (2013) 1222–1225. [12] E.F. Schubert, J.K. Kim, Solid-state light sources getting smart, Science 308 (2005) 1274–1278. [13] S. Tonzani, Lighting technology: time to change the bulb, Nature 459 (2009) 312–314. [14] V. Ramasamy, S.R. Anishia, M.T. Jose, V. Ponnusamy, Synthesis and TL emission properties of RE3+ (Tm, Tb, Ce, Gd and Dy) doped lithium based alkaline (Ca, Mg) earth metal borates, Arch. Phys. Res. 2 (2) (2011) 1. [15] R. Chen, J.L. David, Developments in luminescence and display materials over the last 100 years as reflected in electrochemical society publications, J. Electrochem. Soc. 149 (9) (2002) S69. [16] K. Kim, Y.M. Moon, S. Choi, H.K. Jung, S. Nahm, Luminescent properties of a novel green-emitting gallium borate phosphor under vacuum ultraviolet excitation, Mater. Lett. 62 (24) (2008) 3925–3927. [17] Q.S. Lin, W.D. Cheng, J.T. Chen, J.S. Huang, Crystal and electronic structures and linear optics of strontium pyroborate, J. Solid State Chem. 144 (1999) 30–34. [18] J. Sun, J. Lai, J. Zhu, Z. Xia, H. Du, Luminescence properties and energy transfer investigations of Sr2 B2 O5 :Ce3+ , Tb3+ phosphors, Ceram. Int. 38 (2012) 5341–5345. [19] B. Yan, C. Wang, Synthesis and luminescence properties of REAl3 (BO3 )4 :Eu3+ /Tb3+ (RE = Y, Gd) phosphors from sol–gel composition of hybrid precursors, Solid State Sci. 10 (2008) 82. [20] E.T. Goldburt, B. Kulkarni, R.N. Bhargava, J. Taylor, M. Libera, Size dependent efficiency in Tb doped Y2 O3 nanocrystalline phosphor, J. Lumin. 72/74 (1997) 190. [21] H. Amekura, A. Eckau, R. Carius, C. Buchal, Room-temperature photoluminescence from Tb ions implanted in SiO2 on Si, J. Appl. Phys. 84 (1998) 3867. [22] A. Nag, T.R.N. Kutty, Photoluminescence due to efficient energy transfer from Ce3+ to Tb3+ and Mn2+ in Sr3 Al10 SiO20 , Mater. Chem. Phys. 91 (2005) 524–531. [23] Y.S. Chang, H.J. Lin, Y.C. Li, Y.L. Chai, Y.Y. Tsai, Synthesis and luminescent properties of Tb3+ -activated yttrium indium germanate phosphor, J. Sol. State Chem. 180 (2007) 3076–3081. [24] Thermo Nicolet, Introduction to Fourier Transform Infrared Spectrometry, 2001.
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.de/ijleo
Combustion synthesis of Sr2 B2 O5 :Tb3+ green emitting phosphor for solid state lighting V.R. Panse a , N.S. Kokode b , A.N. Yerpude c,∗ , S.J. Dhoble d a
Department of Applied Physics, NCET Gondwana University, Gadchiroli 442605, India N.H. College, Bramhapuri, Dist-Chandrapur 441206, India Department of Physics, N.H. College, Bramhapuri, Dist-Chandrapur 441206, India d Department of Physics, RTM Nagpur University, Nagpur 440033, India b c
a r t i c l e
i n f o
Article history: Received 2 April 2015 Accepted 9 November 2015 Keywords: Phosphor Borates XRD SEM FTIR
a b s t r a c t Terbium doped Sr2 B2 O5 green phosphor was synthesized by combustion synthesis method at about 550 ◦ C. Further, analyzed by XRD technique and XRD pattern of prepared phosphor is well match with standard JCPDs file. The morphology and structure of the phosphor were characterized by scanning electron microscopy. The chromatic coordinates estimated from emission spectra shown by CIE chromatic diagram and values observed are Cx = 0.263, Cy = 0.723. The vibrational characteristics were studied with the help of FTIR. The excitation and emission spectra specify that the prepared phosphor can be effectively excited by 353 nm and reveal bright green emission centered at 545 nm consequent to the D → F transition of Tb3+ ion. From the obtained results it is concluded that present phosphor may be efficient photoluminescent materials for solid-state lighting and energy saving applications. © 2015 Elsevier GmbH. All rights reserved.
1. Introduction Now a day’s use of tri-color (RGB) phosphor has paying more and more attention has been paid to the preparation of high-efficiency, high chemical stability and low thermal quenching blue, green and red phosphors suitable for energy saving applications [1,2]. White light emitting diodes (w-LEDs) have many advantages, e.g. long lifetime, high luminescence efficiency, high brightness, low energy consumption and environmental-friendliness, they are the most important source and a very bright future in various lighting applications because of their high energy efficiency and cost effectiveness compared to incandescent bulbs. Rare-earth luminescent materials have been widely applied in many fields, such as color television sets, picture tubes, computer monitors, solid state lighting, due to their abundant 4f energy levels of rare-earth ions and their transition properties, Researches on phosphors, particularly, rare earth phosphors for white LED are extremely active [3]. In practically phosphors were paying more and more attention mainly on various oxygen containing inorganic compounds, such as borates, aluminates, silicates, oxides and aluminoborates. Materials based on borate are very helpful classes of hosts material for luminescence because of their high UV transparency and exceptional optical damage threshold [4]. Borates based inorganic
phosphors have paying much attention owing to their low synthesis temperature, high stability, and superior transparency in the UV region [5]. Luminescence properties of the trivalent rare earth activated compounds have received great concentration in the area of solid state lighting as well as white light emitting diode [6,7]. Owing to advantages of white light-emitting diode (LED) such as environmental protection, long lifetime, and low energy consumption is considered as the next generation solid-state light sources for substituting the usually used fluorescent lamps and, incandescent lamps [8–10]. As a host borate compounds played a very important role for the development of luminescent materials [11,14]. As phosphor materials for a several applications [12,13] various borate materials used as a host and doped with rare earth ions and other ions have been reported earlier by various groups [15,16]. We have prepared a borate based green color emitting phosphor activated with trivalent terbium ion for their possible application for energy consumption and solid-state lighting and characterized by X-ray diffraction (XRD), Scanning electron microscopy, photoluminescence spectra, Fourier transform infrared (FT-IR) spectra, chromaticity nature of Sr2 B2 O5 :Tb3+ phosphors. 2. Experimental 2.1. Materials
∗ Corresponding author. Tel.: +91 9637782611. E-mail address: [email protected] (A.N. Yerpude). http://dx.doi.org/10.1016/j.ijleo.2015.11.030 0030-4026/© 2015 Elsevier GmbH. All rights reserved.
In this work, we prepared Sr2 B2 O5 phosphor doped with trivalent terbium ion by using a combustion synthesis method with
1604
V.R. Panse et al. / Optik 127 (2016) 1603–1606
extra heat treatment. Here we used SrNO3 (A.R.) (99.999%), H3 BO3 (A.R.) (99.999%) and NH2 CONH2 (A.R.) (99.999%), from Merck as raw materials to prepare the phosphor material with and without dopant and Tb4 O7 which was added as an activator or called as dopant respectively.
2.2. Preparation of Sr2 B2 O5 :Tb3+ phosphor To synthesize Sr2 B2 O5 :Tb3+ phosphor, chemical compound such as SrNO3 (A.R.) (99.999%), H3 BO3 (A.R.) (99.999%) and NH2 CONH2 (A.R.) (99.999%), from Merck in the stoichiometric ratio were mixed in an agate mortar by adding up an amount of urea as a fuel and then grinded for minimum time duration of 20–30 min each concentration separately. Finally, the mixture was placed into a porcelain crucible and then using vertical furnace, fired at 550 ◦ C in an air atmosphere for very short time duration. After firing, the samples take out from the furnace and then cooled slowly it at room temperature. The product of heated phosphor material obtained was crushed again in an agate mortar, for time duration of 45–60 min each, after that the crushed sample is again fired at 600 ◦ C for 12 h duration in an air atmosphere. After completing heating process the sample slowly cooled and then kept it outside from the furnace. The product of prepared phosphor material obtained was crushed in agate mortar to convert it into fine particle for obtaining fine powder sample.
2.3. Characterization The phase structure of samples obtained in the powder form was confirmed by taking the X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectrometry (IR) studies. The photoluminescence (PL) emission spectra of the samples were recorded using a fluorescence spectrometer (Shimadzu, RF 5301 PC). The photoluminescence spectra, i.e. emission and excitation were recorded using a spectral slit width of 1.5 nm. All the above data were measured and recorded at room temperature. The chromaticity nature is studied with the help of CIE software.
3. Results and discussion 3.1. XRD measurement According to Lin, Cheng et al.’s work [17] and Jiayue Sun et al.’s work [18] the crystal structure of Sr2 B2 O5 phase is belongs to monoclinic crystal structure with a space group of P21/c and the lattice ˚ b = 5.341(1) A, ˚ constants of monoclinic Sr2 B2 O5 are: a = 7.719 (4) A, c = 11.873(2) A˚ and Z = 4. It is well established fact that every crystalline material gives a unique x-ray diffraction pattern. A careful study of diffraction patterns of unknown materials offers a powerful means of qualitative identification of various phases present therein. It is therefore proved to be a quick and non destructive method for an identification of compounds. In addition to this the information obtained on lattice parameters using the x-ray powder diffraction data, gives better insight to structural changes produced in compound by physical or chemical process. These merits put this technique above all, which are, in general, used for structural characterization of material. The XRD pattern of Sr2 B2 O5 along with JCPDS file is shown in Fig. 1, is well match linking the as prepared phosphor material and the JCPDS data (73-1930) was observed. 3.2. SEM micrograph of Sr2 B2 O5 phosphor Fig. 2 shows the SEM micrographs of the combustion synthesized Sr2 B2 O5 phosphor. The images of prepared Sr2 B2 O5 phosphors show the crystallites with agglomerated condition. From Fig. 2 it is clear that crystallite size of the prepared phosphor within the range of micrometer. Owing to growth of huge amount of gases a well expected dense flake foam and rod like morphology is observed. It is clear that the approximate size of the particles might be in micrometer range which is in favor of its application in solid state lighting. Due to their ability of high luminescence with the advantage of micrometer dimension, suggest that this phosphor will find further applications in display and lighting field [19]. 3.3. Photoluminescence properties of Sr2 B2 O5 :Tb3+ phosphor In order to find out whichever prospective uses of the trivalent terbium ions doped with Sr2 B2 O5 phosphors, we have to
Fig. 1. XRD pattern of Sr2 B2 O5 phosphor.
V.R. Panse et al. / Optik 127 (2016) 1603–1606
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Fig. 4. Emission spectrum of Sr2 B2 O5 :Tb3+ phosphor.
Fig. 2. SEM images of Sr2 B2 O5 phosphor.
recognize their photoluminescence spectra, i.e. emission and excitation which was recorded from room temperature to relative temperature. Lots of phosphors which reveal feature of green emission of 5 D4 → 7 F5 transition trivalent terbium ions can be extensively used as luminescent centers [20,21]. The Tb3+ ions used as an activator of green emitting luminescent materials consist of major emission lines peaking at around 422 nm, 439 nm, 463 nm, 491 nm, 545 nm, 588 nm and 625 nm, which are due to the distinctive 5 D3 → 7 F5 , 5 D3 → 7 F4 , 5 D3 → 7 F3 , 5 D4 → 7 F6 , 5 D4 → 7 F5 , 5 D → 7 F and 5 D → 7 F transitions of trivalent terbium ions 4 4 4 3 correspondingly. The photoluminescence emission and excitation measurements are taken at air atmosphere. As shown in Fig. 3, excitation spectrum of Sr2 B2 O5 :Tb3+ phosphor observed at 545 nm emission wavelength consisting of a broad band as well as some sharp lines. The broad band is due to f-d interaction while sharp lines are due to f–f transitions. The emission spectrum as shown in Fig. 4 has sharp lines on account of f–f transition of Tb3+ ions. The emission spectrum usually has major contribution from 5 D4 → FJ (J = 6, 5, 4, 3) but a weak peak around due to 5 D3 → 7 FJ (J = 6, 5,
Fig. 3. Excitation spectrum of Sr2 B2 O5 :Tb3+ phosphor.
4, 3) can also be seen. By the selection rule J = ±1 for electric dipole and J = 0, ±2 for magnetic dipole transitions respectively, the nature of 5 D4 → 7 FJ transitions is governed. The most extreme luminescence emission, i.e. green emission of prepared phosphor observed at 545 nm (5 D4 –7 F5 ), under the excitation of 353 nm. As shown in Fig. 4, the emission intensity of 5 D3 level is very weak and but further increasing with increasing Tb3+ concentration, followed by the enhancement of the emission from the 5 D4 level. As the concentration of Tb3+ is changed, the cross-relaxation effect becomes stronger, which enhances the intensity of green emission at 545 nm. The reason that has been assigned to weak luminescence from 5 D3 level is due to the lack of phonon energy of the host. The smaller the phonon energy of the host at diluted concentrations of terbium ions, the lower will be the 5 D3 emission intensity and vice versa [22,23]. From the emission and excitation of the prepared phosphor we concluded that this become the green emitting phosphor for solid state lighting. The emission observed for the excitation is conclude that the prepared phosphor material become the phosphor material used for solid state lighting having low energy consumption. 4. Fourier transform infrared (FT-IR) of Sr2 B2 O5 phosphors In order to study the molecular and structural environment of the entitled phosphor FTIR spectrum in the range 4600–400 cm−1 was recorded at room temperature by a bruker spectrometer with 40 scans and the resolution of 4.0 cm−1 . A distinctive FTIR spectrum, i.e. Fourier transform infrared radiation, the obtained infrared spectroscopy of combustion synthesized Sr2 B2 O5 phosphor is shown in Fig. 5. In infrared spectroscopy, IR radiation is accepted through a sample prepared. Some of infrared radiation is passed through (transmitted) the sample and some of it is absorbed by the sample. The considerable spectrum of prepared sample represents the
Fig. 5. FTIR spectra of Sr2 B2 O5 phosphors.
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molecular transmission and absorption creating a fingerprint of the sample. As like a fingerprint no two unique molecular structures produce the same infrared spectrum. These terms makes infrared spectroscopy helpful for several types of analysis used for different studies [24]. The B O bond which indicates stretching vibration in [BO3 ] units due to varied groups at 1450 cm−1 . Bending vibrations of H O H band which are due to crystal water included in compound is slightly seen at 1376 cm−1 . The presence of the band at 1150 cm−1 assigned to asymmetric stretching vibrations of trihedral (BO3 ) borate groups. The peak observed at 732 cm−1 , 680 cm−1 wavelength indicates in plane bending vibrations of trihedral (BO3 ) groups. It can classify unidentified materials, also used to determine the excellence or consistency of a prepared sample. It can find out the amount of components in a mixture. From the spectrum it is observed that the prepared phosphor material, i.e. Sr2 B2 O5 without dopant are characterized by nine bands which is shown in figure, with energies ranging from 625 to 1450 cm−1 such as 1450 cm−1 ; 1376 cm−1 ; 1150 cm−1 ; 1010 cm−1 ; 960 cm−1 ; 810 cm−1 ; 732 cm−1 ; 680 cm−1 ; 625 cm−1 corresponds to the formation of the Sr2 B2 O5 phosphor and areas signed to the characteristic metal–oxygen vibrational modes in its configuration. Rare earth ions in general are known to yield good luminescence when used as dopants in different host matrices. 5. Conclusions Tb3+ doped Sr2 B2 O5 green emitting phosphors successfully prepared by combustion method and well matched with standard JCPDS file. From the PL results obtained it is fulfilled that, Sr2 B2 O5 host is suitable for trivalent terbium emission which is peaking at 545 nm, 422 nm, 439 nm, 463 nm, 545 nm, 588 nm, 625 nm, for the excitation of 353 nm due to 5d–4f transition. The strongest green emission observed at 545 nm due to 5 D4 → 7 F5 transition. Morphology of the phosphors shows the rod like structures having micrometer size. Nature of bonding is studied by Fourier transform infrared spectroscopy. The stokes shift and the frequency for the prepared phosphor is found to be 192 nm and 5.76 × 10−15 m respectively The obtained results shows that the prepared phosphors having possible application as a green emitting phosphor which is suitable for energy consumption and solid state lighting. References [1] A. Lakshmanan, R.S. Bhaskar, P.C. Thomas, R.S. Kumar, V.S. Kumar, M.T. Jose, A red phosphor for nUV LED based on (Y,Gd)BO3 :Eu3+ , Mater. Lett. 64 (2010) 1809–1812.
[2] Y. Liu, Z. Yang, A novel green luminescent material AlPO4 :Tb3+ , Mater. Lett. 65 (2011) 1853–1855. [3] G.M. Cai, F. Zheng, D.Q. Yi, Z.P. Jin, X.L. Chen, New promising phosphors Ba3 InB9 O18 activated by Eu3+ /Tb3+ , J. Lumin. 130 (2010) 910–916. [4] K. Kim, Y. Moon, S. Choi, H. Jung, S. Nahm, Luminescent properties of a novel green-emitting gallium borate phosphor under vacuum ultraviolet excitation, Mater. Lett. 62 (2008) 3925–3927. [5] C.K. Lin, M. Yu, M.L. Pang, J. Lin, Photoluminescent properties of sol–gel derived (La, Gd)MgB5 O10 :Ce3+ /Tb3+ nanocrystalline thin films, Opt. Mater. 28 (2006) 913–918. [6] A.N. Yerpude, S.J. Dhoble, Luminescent properties of Eu2+ and Dy3+ ions in Ba4 Al2 O7 phosphor for solid state lighting, J. Lumin. 132 (2012) 1781–1785. [7] K.N. Shinde, S.J. Dhoble, Luminescence in Dy3+ and Eu3+ activated K3 Al2 (PO4 )3 , J. Fluoresc. 21 (2011) 2053–2056. [8] W.J. Yang, L. Luo, T.M. Chen, N.S. Wang, Luminescence and energy transfer of Euand Mn-coactivated CaAl2 Si2 O8 as a potential phosphor for white-light UVLED, Chem. Mater. 17 (15) (2005) 3883–3888. [9] I.M. Nagpure, V.B. Pawade, S.J. Dhoble, Combustion synthesis of Na2 Sr(PO4 )F:Dy3+ white light emitting phosphor, Luminescence 25 (2010) 9–13. [10] Z. Li, J. Zeng, G. Zhang, Y. Li, A new promising phosphor, Na3 La2 (BO3 )3 :Ln (Ln = Eu, Tb), J. Solid State Chem. 178 (2005) 3624–3630. [11] N.S. Bajaj, S.K. Omanwar, Combustion synthesis and characterization of phosphor KSr4 (BO3 )3 :Dy3+ , Opt. Mater. 35 (2013) 1222–1225. [12] E.F. Schubert, J.K. Kim, Solid-state light sources getting smart, Science 308 (2005) 1274–1278. [13] S. Tonzani, Lighting technology: time to change the bulb, Nature 459 (2009) 312–314. [14] V. Ramasamy, S.R. Anishia, M.T. Jose, V. Ponnusamy, Synthesis and TL emission properties of RE3+ (Tm, Tb, Ce, Gd and Dy) doped lithium based alkaline (Ca, Mg) earth metal borates, Arch. Phys. Res. 2 (2) (2011) 1. [15] R. Chen, J.L. David, Developments in luminescence and display materials over the last 100 years as reflected in electrochemical society publications, J. Electrochem. Soc. 149 (9) (2002) S69. [16] K. Kim, Y.M. Moon, S. Choi, H.K. Jung, S. Nahm, Luminescent properties of a novel green-emitting gallium borate phosphor under vacuum ultraviolet excitation, Mater. Lett. 62 (24) (2008) 3925–3927. [17] Q.S. Lin, W.D. Cheng, J.T. Chen, J.S. Huang, Crystal and electronic structures and linear optics of strontium pyroborate, J. Solid State Chem. 144 (1999) 30–34. [18] J. Sun, J. Lai, J. Zhu, Z. Xia, H. Du, Luminescence properties and energy transfer investigations of Sr2 B2 O5 :Ce3+ , Tb3+ phosphors, Ceram. Int. 38 (2012) 5341–5345. [19] B. Yan, C. Wang, Synthesis and luminescence properties of REAl3 (BO3 )4 :Eu3+ /Tb3+ (RE = Y, Gd) phosphors from sol–gel composition of hybrid precursors, Solid State Sci. 10 (2008) 82. [20] E.T. Goldburt, B. Kulkarni, R.N. Bhargava, J. Taylor, M. Libera, Size dependent efficiency in Tb doped Y2 O3 nanocrystalline phosphor, J. Lumin. 72/74 (1997) 190. [21] H. Amekura, A. Eckau, R. Carius, C. Buchal, Room-temperature photoluminescence from Tb ions implanted in SiO2 on Si, J. Appl. Phys. 84 (1998) 3867. [22] A. Nag, T.R.N. Kutty, Photoluminescence due to efficient energy transfer from Ce3+ to Tb3+ and Mn2+ in Sr3 Al10 SiO20 , Mater. Chem. Phys. 91 (2005) 524–531. [23] Y.S. Chang, H.J. Lin, Y.C. Li, Y.L. Chai, Y.Y. Tsai, Synthesis and luminescent properties of Tb3+ -activated yttrium indium germanate phosphor, J. Sol. State Chem. 180 (2007) 3076–3081. [24] Thermo Nicolet, Introduction to Fourier Transform Infrared Spectrometry, 2001.