Influence of modifiers on the spectroscopic properties of Sm3+ ions doped sodium fluoroborate glasses M. Mariyappan, S. Arunkumar, and K. Marimuthu Citation: AIP Conference Proceedings 1665, 070006 (2015); doi: 10.1063/1.4917870 View online: http://dx.doi.org/10.1063/1.4917870 View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1665?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Investigations on optical properties of Sm3+ ion doped boro-phosphate glasses AIP Conf. Proc. 1665, 070040 (2015); 10.1063/1.4917904 Spectroscopic behaviour of Dy3+ ions in lead telluro-fluoroborate glasses for photonic applications AIP Conf. Proc. 1665, 070018 (2015); 10.1063/1.4917882 Photoluminescence properties of Ho 3+ ion in lithium-fluoroborate glass containing different modifier oxides AIP Conf. Proc. 1591, 714 (2014); 10.1063/1.4872729 Investigation of the role of silver species on spectroscopic features of Sm3+-activated sodium–aluminosilicate glasses via Ag+-Na+ ion exchange J. Appl. Phys. 113, 193103 (2013); 10.1063/1.4807313 Optical properties of Eu2O3 doped lead fluoroborate glass AIP Conf. Proc. 1447, 537 (2012); 10.1063/1.4710115
Influence Of Modifiers On The Spectroscopic Properties Of Sm3+ ions Doped Sodium Fluoroborate Glasses M. Mariyappan, S. Arunkumar and K. Marimuthu* Department of Physics, Gandhigram Rural Institute − Deemed University, Gandhigram – 624 302, India *E-mail:
[email protected] Abstract. Effect of Bi2O3/Na2O on the luminescence behavior of Sm3+ ions in Sodium fluoroborate glasses with the composition 40B2O3+xBi2O3+(40−x)Na2CO3+19CaF2+1Sm2O3 (where x= 0, 10, 20 30 and 40 in wt%) have been examined through absorption, luminescence and decay analysis. Optical energy gap (Eopt), Urbach energy (∆E), Bonding parameters (δ), Oscillator strengths (f) and Judd-Ofelt parameters have been determined and their features are reported. By using the JO intensity parameters various radiative properties like transition probability (A), stimulated emission cross-section ( σ PE ), calculated lifetime (τcal), branching ratios (βR) and effective bandwidth (∆λeff) are calculated and reported. The decay curves corresponding to the 4G5/2 excited level of the Sm3+ ions are found to be non-exponential due to the efficient energy transfer between Sm3+–Sm3+ ions and the results have been discussed and reported. Keywords: Absorption, Luminescence, Stimulated emission cross-section, Decay and Cross-relaxation. PACS: 73.61.Jc,74.25.Gz
INTRODUCTION Over the past few decades, rare earth (RE) doped glasses receive much attention due to their vast technological applications in optical fibers, sensors, lasers and broadband communications [1,2]. The Sm3+ ion exhibit strong luminescence in the reddish orange region prescribed for red laser applications and the emission intensity strongly depend on the Sm3+ ion concentration and glass composition [3,4]. Borate glasses possess different advantages like high dielectric constant, high RE ion solubility, high mechanical and chemical strength due to their higher phonon energy over silicate, fluoride, tellurite and phosphate glasses [5,6]. Addition of heavy metal oxides in to the B2O3 network reduces the phonon energy considerably and gives intense fluorescence suitable for lasers and fiber amplifiers [7]. In the present work, composition effect on the spectroscopic behavior of Sm3+ ions doped Sodium fluoroborate glasses have been studied and reported.
EXPERIMENTAL The Sm3+ ions doped Sodium fluoroborate glasses were prepared by melt quenching technique following the procedure reported in literature [4]. The glass codes and the chemical compositions are as follows.
Sm0BiNB :40B2O3+0Bi2O3+ 40Na2CO3+19CaF2+1Sm2O3 Sm10BiNB:40B2O3+10Bi2O3+ 30Na2CO3+19CaF2+1Sm2O3 Sm20BiNB:40B2O3+20Bi2O3+ 20Na2CO3+19CaF2+1Sm2O3 Sm30BiNB:40B2O3+30Bi2O3+ 10Na2CO3+19CaF2+1Sm2O3 Sm40BiNB:40B2O3+40Bi2O3+ 0Na2CO3+19CaF2+1Sm2O3
Optical absorption spectra of the glass samples were recorded using CARY 500, UV−Vis−NIR spectrophotometer in the range of 375−2500 nm with a spectral resolution of ±0.1 nm. The luminescence and lifetime measurements were made using JOBIN YVON Fluorolog-3 Spectrofluorimeter. All these measurements were carried out at RT only.
ABSORPTION SPECTRA Figure 1 shows the absorption spectra of the title glasses which are similar to the reported Sm3+-doped glasses [3]. The absorption spectra exhibit several bands due to the f−f transitions from the 6H5/2 ground state to the various excited states. The spectra exhibit bands at 6504, 6749, 7244, 8117, 9285, 10593, 17794, 18975, 20000, 21277, 21645, 22222, 22831, 23981, 24814, 25641, 26738 and 27778 cm−1 due to the transitions from the 6H5/2 ground state to the various excited states such as 6H15/2+6F1/2, 6F3/2, 6F5/2, 6F7/2, 6 F9/2, 6F11/2, 4G5/2, 4F3/2, 4G7/2, 4I11/2, 4I13/2, 4F5/2, 4G9/2, 4 M19/2, 6P5/2+4P5/2, 4L13/2+4F7/2+6P3/2, 4L15/2 and 6P7/2 respectively.
Solid State Physics AIP Conf. Proc. 1665, 070006-1–070006-3; doi: 10.1063/1.4917870 © 2015 AIP Publishing LLC 978-0-7354-1310-8/$30.00
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TABLE 1. Oscillator strengths (fexp and fcal )(×10−6) of the SmxBiNB glasses and reported Sm3+:glasses
A bsorptionIntensity(a.u.)
6
L13/2+ F7/2+ P3/2
Apsorptionintensity (a.u.)
6 F 7/2
4
4
D3/2
6 F 5/2
6 H 9/2
6 F 3/2
Transition
6 H 15/2
6
4
6 H 13/2
4
1000
1200
1400
1600
4
4
L15/2
2200
2400
Sm30BiNCB Sm20BiNCB
4
I13/2
4
Sm10BiNCB
M19/2
M15/2 +4I9/2 4
Sm0BiNCB
6
400
2000
Sm40BiNCB
4
P5/2
1800
Wavelenth (nm)
4
P7/2
G9/2+ M17/2+ F5/2
6
H15/2 F3/2 6 F5/2 6 F7/2 6 F9/2 6 F11/2 6
6 F 1/2
6 F 11/2
4
4
I11/2+4M15/2+4I9/2 500
I13/2
M17/2 + 4F5/2 6
600
700
800
P5/2 M19/2 4 L13/2 σ
900
4
Wavelength (nm)
FIGURE 1. Absorption spectra of the SmxBiNB glasses [Inset shows the NIR absorption of the Sm0BiNB glass]
The shift of the hypersensitive transitions towards the longer wavelength region is an indication of covalency in the Sm–O bond. This is due to the nephelauxetic effect and arises from the expansion of partially filled ƒ-shell due to the charge transfer from the ligands to the core active ions. The bonding parameters were determined using the nephelauxetic ratios (ߚ) [3,4] and the δ values are found to be −0.113, −0.111, −0.180, −0.182 and −0.220 corresponding to the Sm0BiNB, Sm10BiNB, Sm20BiNB, Sm30BiNB and Sm40BiNB glasses respectively. The negative sign indicates that the prepared glasses possess ionic nature and the ionic nature gradually changes with the change in Bi2O3 content [5].
1SLBTZ [3] fexp fcal 0.38 0.21 1.08 1.28 2.41 2.60 4.51 4.56 3.09 3.06 0.49 0.49 1.15 0.91 0.41 0.57 0.67 0.21 0.50 0.68 0.22 0.00 7.03 5.38 ±0.569
B2TS [4] fexp fcal 0.66 0.95 1.85 1.91 3.45 3.30 2.00 2.20 0.29 0.35 0.41 0.66 0.13 0.41 0.37 0.15 0.15 0.50 0.20 0.00 4.85 3.95 0.36 0.15 ± 0.307
Sm3+ ions due to the increasing proportion of BO4 units and in turn lead to close packing of oxygen atoms around the Sm3+ ions. In general fall in Ωλ parameter values may due to the increase in ioinicity between Sm3+ ions and their surrounding ligands which is further confirmed through the δ values [7,8]. TABLE 2. JO parameters of the prepared SmxBiNB glasses along with the reported Sm3+ doped glasses Glass code Sm0BiNCB Sm10BiNCB Sm20BiNCB Sm30BiNCB Sm40BiNCB 0.5SmPbFB [5] STB [7] Sm3+:CdBiB [8] B2TS [4] 1SLBTZ [3]
JUDD-OFELT INTENSITY PARAMETERS The oscillator strengths have been calculated using the expressions reported in literature [2,3] and the fcal and fexp values are presented in table 1 along with the reported glasses. The oscillator strength values are used to compute the JO intensity parameters [9,10] and their values are presented in table 2. Generally JO intensity parameters relate the local structure and the nature of the bonding in the vicinity of rare earth ions to the surrounding ligands [6,7]. The Ω2 intensity parameter gives information about the structural changes around the rare earth ion site and increases with the asymmetry of the local structure and with the degree of covalency of the RE−O bonds. The higher Ω4 values of the present glasses suggest the higher rigidity [5] and the less Ω2 values imply the less covalent nature of the prepared glasses and higher symmetry around the Sm3+ ions. It is observed from table 2 that Ω2 values decreases from 0.524 to 0.358 (×10−20) with the increasing Bi2O3 content thus indicates the increase in symmetry occupied by the
Sm20BiNB fexp fexp 2.06 2.14 5.16 4.93 12.3 12.5 4.29 4.34 2.62 2.44 0.63 1.08 0.43 0.43 0.12 0.12 0.40 0.40 0.15 0.16 ± 0.302
Ω2 0.524 0.465 0.454 0.415 0.358 0.192 1.490 0.040 0.374 0.374
Ω4 2.182 3.385 4.063 2.371 3.682 3.570 5.680 2.840 3.273 5.802
Ω6 1.735 1.008 0.708 1.060 0.950 2.791 3.330 6.030 2.312 3.529
Ω4/Ω6 1.258 3.358 5.739 2.237 3.876 1.279 1.710 0.470 1.415 1.644
LUMINESCENCE SPECTRA Figure 2 shows the luminescence spectra of the SmxBiNB glasses recorded by monitoring an excitation at 402 nm and is similar to the reported works [1−6]. Emission spectra exhibit four peaks at 565, 602, 647 and 708 nm corresponding to the transitions 4G5/2→6H5/2, 6H7/2, 6H9/2 and 6H11/2 respectively. Among all the transitions, 4G5/2→6H7/2 (Red) exhibit intense emission centered at 602 nm. The 4G5/2→6H7/2 transition is magnetic dipole allowed with the electric dipole domination and the 4 G5/2→6H9/2 transition (Orange) corresponds to electric dipole (ED). The R/O ratio is useful to explain the symmetry around the local environment of the 4f3+ ions. From the obtained JO intensity parameters the radiative properties such as transition probability (A), stimulated emission cross-section ( σ PE ), calculated life
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1
H11/2 Sm40BiNB Sm30BiNB Sm20BiNB
4
I11/2
4
M15/2 4
4
G5/2
601nm
16
12
P5/2
648nm
6
6
565nm
H9/2
4 F7/2 M17/2 4 4 I13/2F5/2 4 I9/2 4 G7/2 4 F3/2 4 G5/2
408nm
6
3
H5/2
20
D3/2 P /2 L157/2
6 4
4
708nm
24
6
Luminescent intensity (a.u.)
4
28
λext=402 nm
H7/2
Energylevel (×10)
6
G5/2→
Norm alisedIntensity(a.u)
4
6
F11/2
F11/2
F11/2 F9/2 F7/2 F5/2 F3/2 6 F 6 1/2 H13 /2 6 H11/2 6 H9/2 6 H7/2 6 H5/2
G5/2
G5/2
6
6
4
4
G5/2
6
F9/2
6
6
6
8
6
F9/2
6
6
4
0
6
H15/2
6
F5/2
6
F5/2
6
6
H5/2
Emissions of Sm3+ ion
F7/2
H5/2
6
H5/2
(B)
(A)
(C)
6
F7/2
6
H5/2 (D)
Cross-relaxation
Sm10BiNB Sm0BiNB
0
2
4
6
8
10
Lifetime (ms) 550
600
650
700
750
FIGURE 3. Decay curves of the SmxBiNB glasses
Wavelength (nm)
FIGURE 2. Luminescence spectra of the SmxBiNB glasses time (τcal) and branching ratios (βR) of the 4G5/2→6H7/2 transition were calculated using the expressions reported in literature [3,4] and their results are presented in table 3. The βR values are found to follow the order as 4G5/2 →6H7/2 > 6H9/2 > 6H5/2 > 6H11/2. The σ PE values are found to be 1.027, 1.102, 1.448, 1.075 and 1.116 for the 4G5/2→6H7/2 transition corresponding to the Sm0BiNB, Sm10BiNB, Sm20BiNB, Sm30BiNB and Sm40BiNB glasses respectively. Among the prepared glasses, Sm20BiNCB glass posses higher transition probability, stimulated emission cross-section and optical gain bandwidth and hence it is suggested for visible laser applications and fiber optic communications. Figure 3 shows the decay curves of the 4G5/2 level which exhibit non-exponential behavior. The non-exponential behavior arises due to the cross-relaxation mechanism and is presented in the inset of figure 3. This cross-relaxation is due to energy transfer from the 4G5/2 excited energy state to the nearby Sm3+ ions in the 6H5/2 ground state. The possible cross-relaxation channels are (4G5/2,6H5/2)→ (4F7/2,6F9/2), (4G5/2,6H5/2)→(4F9/2,6F7/2), (4G5/2,6H5/2)→ (4F5/2,6F11/2) and (4G5/2,6H5/2)→(4F11/2, 6F5/2). The experimental lifetime and the quantum efficiency values are found to be 3.91, 3.85, 3.74, 3.87, 3.89 ms and 63, 66, 71, 68, 67 corresponding to the Sm0BiNB, Sm10BiNB, Sm20BiNB, Sm30BiNB, Sm40BiNB glasses respectively. TABLE 3. The values of λp, ∆eff, σ PE (10−24 cm2), A (s−1) 4 6 and βR for the G5/2→ H7/2 of the SmxBiNB glasses Param eters λp ∆eff σ PE
A βR (ex) βR (cal)
Sm0 BiNB 602 0.734 1.027 71.61 0.406 0.148
Sm10 BiNB 602 0.588 1.102 99.80 0.442 0.307
Sm20 BiNB 603 0.409 1.448 165.1 0.486 0.381
Sm30 BiNB 605 0.522 1.075 106.6 0.440 0.035
Sm40 BiNB 603 0.495 1.116 137.6 0.434 0.036
CONCLUSION The present work reports the composition dependent spectroscopic behavior of Sm3+ ions doped Sodium fluoroborate glasses. JO analysis has been carried out and the fall in Ω2 parameters may be due to the increase in vibration between Sm-ligand bond which is further confirmed through the bonding parameter studies and the increase in symmetry around the Sm3+ ion site. Based on the optical studies it is concluded that Sm3+:Sm20BiNB glass may be used as a laser active medium for red emission corresponding to the 4G5/2→6H7/2 transition.
ACKNOWLEDGMENT One of the authors Prof. K. Marimuthu would like to thank DAE–BRNS, Mumbai, Govt. of India for the sanction of financial support in the form of a major research Project No. 2012/34/49/BRNS/2034, dt. 27/11/2012.
REFERENCES 1. C. R. Kesavulu, C.K. Jayasankar, J. Lumin. 132 (2012) 2802–2809. 2. K.Selvaraju, K. Marimutthu, J. Alloys Compd. 553 (2013) 273 –281. 3. K.Maheshvaran, Linganna, K.Marimuthu, J. Lumin. 131 (2011) 2746−2753. 4. S.Arunkumar, K.Marimuthu, J.Alloys Compd. 565 (2013) 104−114. 5. K.Swapna, S..Mahamuda, A.S.Rao, T.Sasikala, L.R.Moorthy, J. Lumin. 146 (2014) 288−294. 6. S.Sailaja, C.N.Raju, C.A.Reddy, B.D.P.Raju, Y.D.Jho, J. Molecular Struct. 1038 (2013) 29−34. 7. F.Nawaz,M.R.Sahar, S.K.Ghoshal, Asmahani Awang, R.J. Amjad, J. Lumin. 147 (2014) 90−96. 8. B. R. Judd, Phys. Rev. 127 (1962) 750−761. 9. S.Ofelt, J. Chem. Phys. 37 (1962) 511−520.
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