- Email: [email protected]
Preparation and Spectroscopic Studies of Cr3+-doped Aluminium Calcium Sodium Borate Glasses
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 17 (2019) 1831–1836
www.materialstoday.com/proceedings
MRS-Thailand 2017
Preparation and Spectroscopic Studies of Cr3+-doped Aluminium Calcium Sodium Borate Glasses N. Luewarasirikula,*, Y. Ruangthaweepb,c, J. Kaewkhaob,c a
Applied Physics Program, Faculty of Sciences and Technology, Suan Sunandha Rajabhat University, Bangkok, 10300, Thailand Physics Program, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000, Thailand c Center of Excellence in Glass Technology and Materials Science (CEGM), Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000, Thailand b
Abstract Aluminium calcium sodium borate glasses doped with different concentrations of chromium(III) oxide have been prepared by melt-quenching technique with chemical compositions of 20Al2O3:20CaO:20Na2O:(40-x)B2O3:xCr2O3 where (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mol%). All Cr3+-doped glass samples show clear and transparent with green color center. The densities of the Cr3+-doped samples are around 2.48 to 2.49 g/cm3 while the refractive indexes are around 1.54 to 1.55. The optical absorption spectra show the absorption band at around 604 nm corresponding to the 4A2g→4T2g transition of Cr3+ ions. The excitation spectra consists of two broad bands at around 423 and 567 nm related to the transitions from the ground state 4A2g to the excited states 4T1g and 4T2g, respectively. The emission spectra, excited with 567 nm excitation wavelength, show the band at 690 nm related to the 2Eg→4A2g transition. The emitted light determined by the CIE 1931 chromaticity diagram is shown in red region. The calculated value of Dq/B = 2.28 indicates that the Cr3+ ions in the glass samples are center in intermediate crystal field site which lies between strong and weak crystal field. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of The First Materials Research Society of Thailand International Conference. Keywords: Borate glass; Photoluminescence; Optical absorption; Cr3+
* Corresponding author. Tel.: +66 89179 6223.; fax: +662-160-1010 E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of The First Materials Research Society of Thailand International Conference.
1832
N. Luewarasirikul et al. / Materials Today: Proceedings 17 (2019) 1831–1836
1. Introduction Borate host glass is considered as one of the promising host glass due to many good properties, such as low melting point, moisture resistance, high thermal stability and good optical properties. Borate glass can also accept the transition metal and rare earth ions as efficient dopants [1-4]. Sodium is added to reduce the melting temperature of the glass, while calcium is added to improve the moisture and chemical resistance [5-7]. Aluminium is also used in his work to improve the mechanical stability and there have been some studies on the luminescence enhancement of luminescence glass by aluminium [8]. Cr3+ is commonly doped to generate the green color center of the glass. But in the last decade, Cr3+-doped glass was rapidly studied due to its potential for using as VIS-NIR luminescence material and tunable solid state laser. Luminescence material with Cr3+ ions exhibit intense red color emission that may be considered as cost effective red emission material when compared with the high cost Eu2O3 [9-10]. In this work, aluminium calcium sodium borate glasses doped with different concentrations of chromium(III) oxide with chemical composition 20Al2O3:20CaO:20Na2O:(40-x)B2O3:xCr2O3 where (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mol%) were prepared by melt-quenching technique. The density, refractive index, absorption spectra, CIE L*a*b* color coordinates, excitation and emission spectra, luminescence decay time and CIE 1931 chromaticity diagram of the glass samples had been investigated. 2. Experimental details The glass samples in this work were obtained by melt-quenching technique with chemical compositions of 20Al2O3:20CaO:20Na2O:(40-x)B2O3:xCr2O3 where (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mol%). Appropriate amounts of boric acid (H3BO3), sodium carbonate (Na2CO3), calcium oxide (CaO), aluminum oxide (Al2O3) and chromium(III) oxide (Cr2O3) were mixed and ground in an agate mortar before moved to alumina crucible. The chemical mixtures were melted in an electric furnace at 1150 C for 3 hours. The melts were then moved to annealed in an annealing furnace at 500 C for 3 hours for relieved mechanical stress, before slowly cooled down to room temperature. The glass samples were cut and finely polished for improve the optical properties. The density was carried out in this work by Archimedes’ principle. The refractive index was observed by ATAGO-3T Abbe refractometer with mono-bromonaphthalene as an adhesive coating. The absorption spectra were measured by Cary-50 UV-Vis spectrophotometer in the range of 300 to 1100 nm. The CIE L*a*b* color coordinates were also evaluated by Cary-50 UV-Vis spectrophotometer. The luminescence spectra (excitation spectra, emission spectra and luminescence decay time) were measured by Agilent Cary Eclipse fluorescence spectrophotometer. The color of the emitted light was studied in the framework of the CIE 1931 chromaticity diagram. 3. Result and discussion The well-cut and polished glass samples are shown in Fig. 1, all the glass samples are clear and transparent. The undoped glass shows no color center, while the glasses with 0.01 to 0.05 mol% of Cr2O3 show green color center. The color of the Cr3+-doped glasses tend to darker green with increasing of Cr2O3 concentration. The result shows that even the glasses doped with small amounts of Cr2O3 (0.01 to 0.05 mol%), the green color center of the glasses can be occurred.
Fig. 1. The photograph of the glass samples.
N. Luewarasirikul / Materials Today: Proceedings 17 (2019) 1831–1836
1833
The density and refractive index of the glass samples are shown in Table 1. The density of the undoped glass is lower than the Cr3+-doped glasses due to the higher molecular weight of Cr2O3 than B2O3, while the density of the Cr3+-doped glasses are slightly vary around 2.4816 to 2.4882 g/cm3. The density is not to be the trend when increasing the Cr2O3 concentration, because there are small amounts of Cr2O3 doped in the glass samples (0.01 to 0.05 mol%). The refractive index is the property that related to the density of the medium, so the refractive index of the undoped glass is lower than the Cr3+-doped glasses too. The refractive index of the Cr3+-doped glasses is slightly vary around 1.5457 to 1.5478 and also not to be the trend when increasing the Cr2O3 concentration. Table 1. Density and refractive index of the glass samples. Cr2O3 concentration (mol%) 0.00
Density (g/cm3) 2.4158
0.01
2.4882
1.5478
0.02
2.4816
1.5467
0.03
2.4872
1.5460
0.04
2.4869
1.5457
0.05
2.4827
1.5476
Refractive index 1.5335
The absorption spectra recorded from 300 to 1100 nm are shown in Fig. 2. The spectra exhibit one broad absorption band at 604 nm corresponding to the 4A2g→4T2g transition of Cr3+ ions. The result shows that the peaks of absorption band increase with increasing of Cr2O3 concentration, because the glass samples can absorb more energy when the glasses contained more Cr3+ ions [9-12]. The absorption band located at 604 nm, means the glass samples absorb only the red light from the visible light region. Because green is a complementary color of red, then the more absorption band at 604 nm (reddish orange), the darker green color center of the glass sample occurs (the same trend as shown in the photograph in Fig. 1).
Fig. 2. The absorption spectra of the glass samples.
Fig. 3. The CIE L*a*b* color coordinates of the glass samples.
1834
N. Luewarasirikul et al. / Materials Today: Proceedings 17 (2019) 1831–1836
The CIE L*a*b* color coordinates of the Cr3+-doped glass samples are shown in Fig. 3. The color coordinates show that the color centers of the glass samples are actually located in the greenish-yellow region. When doping more Cr3+, the more -a* (green) and +b* (yellow) are occur, that exhibit the more green (actually greenish-yellow) color center of the glass samples. So the results from the CIE L*a*b* color coordinates are corresponding to the results from the absorption spectra. The excitation spectra (Fig. 4), observed with 690 nm emission wavelength, exhibit the two excitation broad bands at 423 and 567 nm related to the transitions from the ground state 4A2g to the excited states 4T1g and 4T2g, respectively. The peaks of the excitation bands are trend to increase with the increasing of Cr2O3 doped in the glasses. The emission spectra (Fig. 5), excited by the appropriate wavelength at 567 nm, exhibit the band at 690 nm. This emission band is a superposition of a relative narrow 2Eg→4A2g transition due to the Cr3+ ions center in strong crystal field site and a broad 4T2g→4A2g transition due to the Cr3+ ions center in weak crystal field site. The emission spectra in this work show the appearance of both narrow and broad transitions, means the Cr3+ ions in this work are center in intermediate crystal field site which lies between strong and weak crystal field [1,9-12]. The peaks of the emission bands are increase with the increasing of Cr2O3 doped in the glasses. The color of the emitted light, determined by the CIE 1931 chromaticity diagram, of all the glass samples are found to be approximated the same at (0.71, 0.28) located in red region. Fig. 6 presents the location of x,y color coordinate of the glass samples on the CIE 1931 chromaticity diagram. The luminescence decay times were measured by exciting the glass samples with 567 nm excitation wavelength and then observing at 690 nm emission wavelength. The luminescence decay times are found to be 0.264, 0.268, 0.269, 0.274 and 0.275 ms for the glass samples that doped with 0.01, 0.02, 0.03, 0.04 and 0.05 mol% of Cr2O3, respectively. The decay times are slightly increase when increasing the concentration of Cr2O3 doped in the glass samples due to the more Cr3+ luminescence ions contained in the glasses.
Fig. 4. The excitation spectra of the glass samples observed with 690 nm emission wavelength.
N. Luewarasirikul / Materials Today: Proceedings 17 (2019) 1831–1836
Fig. 5. The emission spectra of the glass samples excited by 567 nm excitation wavelength.
This work
Fig. 6. The CIE 1931 chromaticity diagram.
1835
1836
N. Luewarasirikul et al. / Materials Today: Proceedings 17 (2019) 1831–1836
The crystal field strength, Dq and Racah parameters, B can be evaluated from the following equation [4]: where the energy (wavenumber) of the 4A2g→4T2g transition from the absorption spectra is equal to 10Dq and Dq 15( x 8) 2 B ( x 10 x) x
E Dq
(1) (2)
where E stand for the difference of the energy between 4A2g→4T1g transition and 4A2g→4T2g transition. The ratio of Dq / B indicates the strength of crystal field site where Cr3+ ions center in. The value higher than 2.3 is corresponding to strong crystal field, while the value lower than 2.3 is corresponding to weak crystal field [9-10]. In this work, the calculated Dq / B values of all the glass samples are approximated the same as 2.28, this result indicates that the Cr3+ ions in the glass samples are center in intermediate crystal field site, corresponding to the result from the emission spectra. 4. Conclusion
The glass samples in this work were obtained by melt-quenching technique with the chemical compositions of 20Al2O3:20CaO:20Na2O:(40-x)B2O3:xCr2O3 where (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mol%). All the glass samples are clear and transparent, the glasses with 0.01 to 0.05 mol% of Cr2O3 show green color center. The spectra exhibit one broad absorption band at 604 nm corresponding to the 4A2g→4T2g transition of Cr3+ ions. The excitation spectra, observed with 690 nm emission wavelength, exhibit the two excitation broad bands at 423 and 567 nm related to the 4A2g→4T1g transition and the 4A2g→4T2g transition, respectively. The emission spectra, excited by the appropriate wavelength at 567 nm, exhibit the band at 690 nm. The color of the emitted light, determined by the CIE 1931 chromaticity diagram, is located in red region. The luminescence decay times are found to be 0.264, 0.268, 0.269, 0.274 and 0.275 ms for the glass samples that doped with 0.01, 0.02, 0.03, 0.04 and 0.05 mol% of Cr2O3, respectively. The calculated value of Dq/B = 2.28 indicates that the Cr3+ ions in the glass samples are center in intermediate crystal field site which lies between strong and weak crystal field, this result corresponding to the result from the emission spectra. Acknowledgements
The authors would like to thanks Suan Sunandha Rajabhat University (SSRU) and Center of Excellence in Glass Technology and Materials Science (CEGM), Nakhon Pathom Rajabhat University (NPRU) for supporting this research. References [1] [2] [3] [4]
T. Lesniewski, B.V. Padlyak, J. Barzowska, S. Mahlik, V.T. Adamiv, Z. Nurgul, M. Grinberg, Opt. Mater. 59 (2016) 120–125. M.V. Rao, B.Shanmugavelu, V.V. Ravi Kanth Kumar, J. Lumin. 181 (2017) 291–298. S. Azizan, S. Hashim, N. Razak, M. Mhareb, Y. Alajerami, N. Tamchek, J. Mol. Struct. 1076 (2014) 20-25. W. Kuznik, I. Fuks-Janczarek, A. Wojciechowski, I.V. Kityk, V. Kiisk, A. Majchrowski, L.R. Jaroszewicz, M.G. Brik, G.U.L. Nagy, Spectrochim. Acta Mol. Biomol. Spectrosc. 145 (2015) 325–328. [5] A.B. Edathazhe, H.D. Shashikala, Mater. Chem. Phys. 184 (2016) 146-154. [6] M.V. Rao, B.Shanmugavelu, V.V. Ravi Kanth Kumar, J. Lumin. 181 (2017) 291–298. [7] S. Li, H. Liu, F.Wu, Z. Chang, Y. Yue, J. Non-cryst. Solids 434 (2016) 108-114. [8] S. Rai, A.L. Fanai, J. Non-cryst. Solids 449 (2016) 113–118. [9] T.Narendrudu, S.Suresh, G.Chinna Ram, N.Veeraiah, D.Krishna Rao, J. Lumin. 183 (2017) 17–25. [10] F.S. De Vicente, F.A. Santos, B.S. Simoes, S.T. Dias, M. Siu Li, Opt. Mater. 38 (2014) 119–125. [11] T. Kato, G. Okada, T. Yanagida, Opt. Mater. 54 (2016) 134–138. [12] B.V. Padlyak, W. Ryba-Romanowski, R. Lisiecki, V.T. Adamiv, Ya.V. Burak, I.M. Teslyuk, Opt. Mater. 34 (2012) 2112–2119.
ScienceDirect Materials Today: Proceedings 17 (2019) 1831–1836
www.materialstoday.com/proceedings
MRS-Thailand 2017
Preparation and Spectroscopic Studies of Cr3+-doped Aluminium Calcium Sodium Borate Glasses N. Luewarasirikula,*, Y. Ruangthaweepb,c, J. Kaewkhaob,c a
Applied Physics Program, Faculty of Sciences and Technology, Suan Sunandha Rajabhat University, Bangkok, 10300, Thailand Physics Program, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000, Thailand c Center of Excellence in Glass Technology and Materials Science (CEGM), Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000, Thailand b
Abstract Aluminium calcium sodium borate glasses doped with different concentrations of chromium(III) oxide have been prepared by melt-quenching technique with chemical compositions of 20Al2O3:20CaO:20Na2O:(40-x)B2O3:xCr2O3 where (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mol%). All Cr3+-doped glass samples show clear and transparent with green color center. The densities of the Cr3+-doped samples are around 2.48 to 2.49 g/cm3 while the refractive indexes are around 1.54 to 1.55. The optical absorption spectra show the absorption band at around 604 nm corresponding to the 4A2g→4T2g transition of Cr3+ ions. The excitation spectra consists of two broad bands at around 423 and 567 nm related to the transitions from the ground state 4A2g to the excited states 4T1g and 4T2g, respectively. The emission spectra, excited with 567 nm excitation wavelength, show the band at 690 nm related to the 2Eg→4A2g transition. The emitted light determined by the CIE 1931 chromaticity diagram is shown in red region. The calculated value of Dq/B = 2.28 indicates that the Cr3+ ions in the glass samples are center in intermediate crystal field site which lies between strong and weak crystal field. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of The First Materials Research Society of Thailand International Conference. Keywords: Borate glass; Photoluminescence; Optical absorption; Cr3+
* Corresponding author. Tel.: +66 89179 6223.; fax: +662-160-1010 E-mail address: [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of The First Materials Research Society of Thailand International Conference.
1832
N. Luewarasirikul et al. / Materials Today: Proceedings 17 (2019) 1831–1836
1. Introduction Borate host glass is considered as one of the promising host glass due to many good properties, such as low melting point, moisture resistance, high thermal stability and good optical properties. Borate glass can also accept the transition metal and rare earth ions as efficient dopants [1-4]. Sodium is added to reduce the melting temperature of the glass, while calcium is added to improve the moisture and chemical resistance [5-7]. Aluminium is also used in his work to improve the mechanical stability and there have been some studies on the luminescence enhancement of luminescence glass by aluminium [8]. Cr3+ is commonly doped to generate the green color center of the glass. But in the last decade, Cr3+-doped glass was rapidly studied due to its potential for using as VIS-NIR luminescence material and tunable solid state laser. Luminescence material with Cr3+ ions exhibit intense red color emission that may be considered as cost effective red emission material when compared with the high cost Eu2O3 [9-10]. In this work, aluminium calcium sodium borate glasses doped with different concentrations of chromium(III) oxide with chemical composition 20Al2O3:20CaO:20Na2O:(40-x)B2O3:xCr2O3 where (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mol%) were prepared by melt-quenching technique. The density, refractive index, absorption spectra, CIE L*a*b* color coordinates, excitation and emission spectra, luminescence decay time and CIE 1931 chromaticity diagram of the glass samples had been investigated. 2. Experimental details The glass samples in this work were obtained by melt-quenching technique with chemical compositions of 20Al2O3:20CaO:20Na2O:(40-x)B2O3:xCr2O3 where (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mol%). Appropriate amounts of boric acid (H3BO3), sodium carbonate (Na2CO3), calcium oxide (CaO), aluminum oxide (Al2O3) and chromium(III) oxide (Cr2O3) were mixed and ground in an agate mortar before moved to alumina crucible. The chemical mixtures were melted in an electric furnace at 1150 C for 3 hours. The melts were then moved to annealed in an annealing furnace at 500 C for 3 hours for relieved mechanical stress, before slowly cooled down to room temperature. The glass samples were cut and finely polished for improve the optical properties. The density was carried out in this work by Archimedes’ principle. The refractive index was observed by ATAGO-3T Abbe refractometer with mono-bromonaphthalene as an adhesive coating. The absorption spectra were measured by Cary-50 UV-Vis spectrophotometer in the range of 300 to 1100 nm. The CIE L*a*b* color coordinates were also evaluated by Cary-50 UV-Vis spectrophotometer. The luminescence spectra (excitation spectra, emission spectra and luminescence decay time) were measured by Agilent Cary Eclipse fluorescence spectrophotometer. The color of the emitted light was studied in the framework of the CIE 1931 chromaticity diagram. 3. Result and discussion The well-cut and polished glass samples are shown in Fig. 1, all the glass samples are clear and transparent. The undoped glass shows no color center, while the glasses with 0.01 to 0.05 mol% of Cr2O3 show green color center. The color of the Cr3+-doped glasses tend to darker green with increasing of Cr2O3 concentration. The result shows that even the glasses doped with small amounts of Cr2O3 (0.01 to 0.05 mol%), the green color center of the glasses can be occurred.
Fig. 1. The photograph of the glass samples.
N. Luewarasirikul / Materials Today: Proceedings 17 (2019) 1831–1836
1833
The density and refractive index of the glass samples are shown in Table 1. The density of the undoped glass is lower than the Cr3+-doped glasses due to the higher molecular weight of Cr2O3 than B2O3, while the density of the Cr3+-doped glasses are slightly vary around 2.4816 to 2.4882 g/cm3. The density is not to be the trend when increasing the Cr2O3 concentration, because there are small amounts of Cr2O3 doped in the glass samples (0.01 to 0.05 mol%). The refractive index is the property that related to the density of the medium, so the refractive index of the undoped glass is lower than the Cr3+-doped glasses too. The refractive index of the Cr3+-doped glasses is slightly vary around 1.5457 to 1.5478 and also not to be the trend when increasing the Cr2O3 concentration. Table 1. Density and refractive index of the glass samples. Cr2O3 concentration (mol%) 0.00
Density (g/cm3) 2.4158
0.01
2.4882
1.5478
0.02
2.4816
1.5467
0.03
2.4872
1.5460
0.04
2.4869
1.5457
0.05
2.4827
1.5476
Refractive index 1.5335
The absorption spectra recorded from 300 to 1100 nm are shown in Fig. 2. The spectra exhibit one broad absorption band at 604 nm corresponding to the 4A2g→4T2g transition of Cr3+ ions. The result shows that the peaks of absorption band increase with increasing of Cr2O3 concentration, because the glass samples can absorb more energy when the glasses contained more Cr3+ ions [9-12]. The absorption band located at 604 nm, means the glass samples absorb only the red light from the visible light region. Because green is a complementary color of red, then the more absorption band at 604 nm (reddish orange), the darker green color center of the glass sample occurs (the same trend as shown in the photograph in Fig. 1).
Fig. 2. The absorption spectra of the glass samples.
Fig. 3. The CIE L*a*b* color coordinates of the glass samples.
1834
N. Luewarasirikul et al. / Materials Today: Proceedings 17 (2019) 1831–1836
The CIE L*a*b* color coordinates of the Cr3+-doped glass samples are shown in Fig. 3. The color coordinates show that the color centers of the glass samples are actually located in the greenish-yellow region. When doping more Cr3+, the more -a* (green) and +b* (yellow) are occur, that exhibit the more green (actually greenish-yellow) color center of the glass samples. So the results from the CIE L*a*b* color coordinates are corresponding to the results from the absorption spectra. The excitation spectra (Fig. 4), observed with 690 nm emission wavelength, exhibit the two excitation broad bands at 423 and 567 nm related to the transitions from the ground state 4A2g to the excited states 4T1g and 4T2g, respectively. The peaks of the excitation bands are trend to increase with the increasing of Cr2O3 doped in the glasses. The emission spectra (Fig. 5), excited by the appropriate wavelength at 567 nm, exhibit the band at 690 nm. This emission band is a superposition of a relative narrow 2Eg→4A2g transition due to the Cr3+ ions center in strong crystal field site and a broad 4T2g→4A2g transition due to the Cr3+ ions center in weak crystal field site. The emission spectra in this work show the appearance of both narrow and broad transitions, means the Cr3+ ions in this work are center in intermediate crystal field site which lies between strong and weak crystal field [1,9-12]. The peaks of the emission bands are increase with the increasing of Cr2O3 doped in the glasses. The color of the emitted light, determined by the CIE 1931 chromaticity diagram, of all the glass samples are found to be approximated the same at (0.71, 0.28) located in red region. Fig. 6 presents the location of x,y color coordinate of the glass samples on the CIE 1931 chromaticity diagram. The luminescence decay times were measured by exciting the glass samples with 567 nm excitation wavelength and then observing at 690 nm emission wavelength. The luminescence decay times are found to be 0.264, 0.268, 0.269, 0.274 and 0.275 ms for the glass samples that doped with 0.01, 0.02, 0.03, 0.04 and 0.05 mol% of Cr2O3, respectively. The decay times are slightly increase when increasing the concentration of Cr2O3 doped in the glass samples due to the more Cr3+ luminescence ions contained in the glasses.
Fig. 4. The excitation spectra of the glass samples observed with 690 nm emission wavelength.
N. Luewarasirikul / Materials Today: Proceedings 17 (2019) 1831–1836
Fig. 5. The emission spectra of the glass samples excited by 567 nm excitation wavelength.
This work
Fig. 6. The CIE 1931 chromaticity diagram.
1835
1836
N. Luewarasirikul et al. / Materials Today: Proceedings 17 (2019) 1831–1836
The crystal field strength, Dq and Racah parameters, B can be evaluated from the following equation [4]: where the energy (wavenumber) of the 4A2g→4T2g transition from the absorption spectra is equal to 10Dq and Dq 15( x 8) 2 B ( x 10 x) x
E Dq
(1) (2)
where E stand for the difference of the energy between 4A2g→4T1g transition and 4A2g→4T2g transition. The ratio of Dq / B indicates the strength of crystal field site where Cr3+ ions center in. The value higher than 2.3 is corresponding to strong crystal field, while the value lower than 2.3 is corresponding to weak crystal field [9-10]. In this work, the calculated Dq / B values of all the glass samples are approximated the same as 2.28, this result indicates that the Cr3+ ions in the glass samples are center in intermediate crystal field site, corresponding to the result from the emission spectra. 4. Conclusion
The glass samples in this work were obtained by melt-quenching technique with the chemical compositions of 20Al2O3:20CaO:20Na2O:(40-x)B2O3:xCr2O3 where (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mol%). All the glass samples are clear and transparent, the glasses with 0.01 to 0.05 mol% of Cr2O3 show green color center. The spectra exhibit one broad absorption band at 604 nm corresponding to the 4A2g→4T2g transition of Cr3+ ions. The excitation spectra, observed with 690 nm emission wavelength, exhibit the two excitation broad bands at 423 and 567 nm related to the 4A2g→4T1g transition and the 4A2g→4T2g transition, respectively. The emission spectra, excited by the appropriate wavelength at 567 nm, exhibit the band at 690 nm. The color of the emitted light, determined by the CIE 1931 chromaticity diagram, is located in red region. The luminescence decay times are found to be 0.264, 0.268, 0.269, 0.274 and 0.275 ms for the glass samples that doped with 0.01, 0.02, 0.03, 0.04 and 0.05 mol% of Cr2O3, respectively. The calculated value of Dq/B = 2.28 indicates that the Cr3+ ions in the glass samples are center in intermediate crystal field site which lies between strong and weak crystal field, this result corresponding to the result from the emission spectra. Acknowledgements
The authors would like to thanks Suan Sunandha Rajabhat University (SSRU) and Center of Excellence in Glass Technology and Materials Science (CEGM), Nakhon Pathom Rajabhat University (NPRU) for supporting this research. References [1] [2] [3] [4]
T. Lesniewski, B.V. Padlyak, J. Barzowska, S. Mahlik, V.T. Adamiv, Z. Nurgul, M. Grinberg, Opt. Mater. 59 (2016) 120–125. M.V. Rao, B.Shanmugavelu, V.V. Ravi Kanth Kumar, J. Lumin. 181 (2017) 291–298. S. Azizan, S. Hashim, N. Razak, M. Mhareb, Y. Alajerami, N. Tamchek, J. Mol. Struct. 1076 (2014) 20-25. W. Kuznik, I. Fuks-Janczarek, A. Wojciechowski, I.V. Kityk, V. Kiisk, A. Majchrowski, L.R. Jaroszewicz, M.G. Brik, G.U.L. Nagy, Spectrochim. Acta Mol. Biomol. Spectrosc. 145 (2015) 325–328. [5] A.B. Edathazhe, H.D. Shashikala, Mater. Chem. Phys. 184 (2016) 146-154. [6] M.V. Rao, B.Shanmugavelu, V.V. Ravi Kanth Kumar, J. Lumin. 181 (2017) 291–298. [7] S. Li, H. Liu, F.Wu, Z. Chang, Y. Yue, J. Non-cryst. Solids 434 (2016) 108-114. [8] S. Rai, A.L. Fanai, J. Non-cryst. Solids 449 (2016) 113–118. [9] T.Narendrudu, S.Suresh, G.Chinna Ram, N.Veeraiah, D.Krishna Rao, J. Lumin. 183 (2017) 17–25. [10] F.S. De Vicente, F.A. Santos, B.S. Simoes, S.T. Dias, M. Siu Li, Opt. Mater. 38 (2014) 119–125. [11] T. Kato, G. Okada, T. Yanagida, Opt. Mater. 54 (2016) 134–138. [12] B.V. Padlyak, W. Ryba-Romanowski, R. Lisiecki, V.T. Adamiv, Ya.V. Burak, I.M. Teslyuk, Opt. Mater. 34 (2012) 2112–2119.