Mon, December 16, 2019   Advanced Search

Spectroscopic Properties of Eu3+ Doped in Zinc Lithium Bismuth Borate Glasses

S. L. Meena

Ceremic Laboratory, Department of Physics, Jai Narain Vyas University, Jodhpur 342001(Raj.) INDIA.
email address:shankardiya7@rediffmail.com

(Received on: September 30, Accepted: November 4, 2017)

Abstract

Glass sample of Zinc Lithium Bismuth Borate (25-x) Bi2o3:20Li2O: 20ZnO:35 B2O3: x Eu2O3. (where x=1,1.5,2 mol%) have been prepared by melt-quenching technique. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction. The absorption spectra of three Eu3+ doped zinc lithium bismuth borate glasses have been recorded at room temperature. The various interaction parameters like Slater-Condon parameters FK (k=2,4,6), Lande parameter (ζ4F), nephelauexetic ratio (β'),bonding parameter (b1/2)and Racah parameters EK(k=1,2 3) have been computed. Judd-Ofelt intensity parameters and laser parameters have also been calculated.

Keywords:Zinc lithium bismuth borate glasses, Energy interaction parameters, Optical properties, Judd-Ofelt analysis.

Introduction

Among various glasses, borate glasses are excellent host matrices because boric oxide (B2O3) acts as a good glass former and flux material1. Bi2o3 have attracted attention in recent years because of their wide range of applications in the field of glass ceramics, optical and optoelectronic devices2,3. The addition of network modifier (NWF) Li2O is to improve both electrical and mechanical properties of such glasses4. ZnO is a wide band gap semiconductor and has received increasing research interest. It is an important multifunctional material due to its specific chemical, surface and micro structural properties5,6. The past literature shows that the rare earth ions find more important application in the preparation of the laser materials7-10. A survey of the literature shows that there are many reports available on ternary bismuth borate glasses12,13. Bismuth in glasses plays a dual role as a glass network former (NWF) at high concentration and a modifier (NWM) at low concentration14.

Among various glasses, borate glasses are excellent host matrices because boric oxide (B2O3) acts as a good glass former and flux material1. Bi2o3 have attracted attention in recent years because of their wide range of applications in the field of glass ceramics, optical and optoelectronic devices2,3. The addition of network modifier (NWF) Li2O is to improve both electrical and mechanical properties of such glasses4. ZnO is a wide band gap semiconductor and has received increasing research interest. It is an important multifunctional material due to its specific chemical, surface and micro structural properties5,6. The past literature shows that the rare earth ions find more important application in the preparation of the laser materials7-10. A survey of the literature shows that there are many reports available on ternary bismuth borate glasses12,13. Bismuth in glasses plays a dual role as a glass network former (NWF) at high concentration and a modifier (NWM) at low concentration14.
The aim of the present study is to prepare the Eu3+ doped zinc lithium bismuth borate glass with different Eu2O3 concentrations. The absorption spectra, fluorescence spectra of Eu3+of the glasses were investigated. The Judd-Ofelt theory has been applied to compute the intensity parameters Ωλ (λ=2, 4, 6).These intensity parameter have been used to evaluate optical optical properties such as spontaneous emission probability, branching ratio, radiative life time and stimulated emission cross section.

2.Experimental Techniques

Preparation of glasses

The following Eu3+ doped bismuth borate glass samples (25-x) Bi2O3:20Li2O:20ZnO: 35 B2O3: x Eu2O3 (where x=1,1.5, 2) have been prepared by melt-quenching method. Analytical reagent grade chemical used in the present study consist of Bi2O3, Li2O, ZnO, and B2O3and Eu2O3. They were thoroughly mixed by using an agate pestle mortar. then melted at 10500C by an electrical muffle furnace for 2h., After complete melting, the melts were quickly poured in to a preheated stainless steel mould and annealed at temperature of 3500C for 2h to remove thermal strains and stresses. Every time fine powder of cerium oxide was used for polishing the samples. The glass samples so prepared were of good optical quality and were transparent. The chemical compositions of the glasses with the name of samples are summarized in Table 1.

Table 1

Chemical composition of the glasses

Sample   Glass composition (mol %)
ZnLiBiB (UD)   25 Bi2O3:20Li2O:20ZnO: 35 B2O3
ZnLiBiB (EU1)   24 Bi2O3:20Li2O:20ZnO: 35 B2O3: 1 Eu2O3
ZnLiBiB (EU 1.5)   23.5 Bi2O3:20Li2O:20ZnO: 35 B2O3: 1.5 Eu2O3
ZnLiBiB (EU2)   23 Bi2O3:20Li2O:20ZnO: 35 B2O3: 2 Eu2O3

ZnLiBiB (UD) -Represents undoped Zinc Lithium Bismuth Borate glass specimen.
ZnLiBiB (EU) -Represents Eu3+ doped Zinc Lithium Bismuth Borate glass specimens.

3. Theory

3.1 Oscillator Strength

The spectral intensity is expressed in terms of oscillator strengths using the relation15.

Where, ε (ν) is molar absorption coefficient at a given energy ν (cm-1), to be evaluated from Beer–Lambert law.

Under Gaussian Approximation, using Beer-Lambert law, the observed oscillator strengths of the absorption bands have been experimentally calculated16, using the modified relation:

Where c is the molar concentration of the absorbing ion per unit volume, l is the optical path length, logI0/I is optical density and Δυ1/2 is half band width.

3.2. Judd-Ofelt Intensity Parameters

According to Judd17 and Ofelt18 theory, independently derived expression for the oscillator strength of the induced forced electric dipole transitions between an initial J manifold |4fN (S, L) J> level and the terminal J' manifold |4fN (S',L') J'> is given by:

Where, the line strength S (J, J') is given by the equation

In the above equation m is the mass of an electron, c is the velocity of light, ν is the wave number of the transition, h is Planck's constant, n is the refractive index, J and J' are the total angular momentum of the initial and final level respectively, Ωλ (λ = 2, 4, 6) are known as Judd-Ofelt intensity parameters which contain the effect of the odd-symmetry crystal field terms, radial integrals and energy denominators. ||U (λ)||2 are the matrix elements of the doubly reduced unit tensor operator calculated in intermediate coupling approximation. Ωλ parameter can be obtained from least square fitting method19.

The Ωλ parameters obtained using the absorption spectral results have been used to predict radiative properties such as spontaneous emission probability (A) and radiative life time (τR), and laser parameters like fluorescence branching ratio (βR) and stimulated emission cross section (σp).
The spontaneous emission probability from initial manifold |4fN (S', L') J'> to a final manifold |4fN (S, L) J >| is given by:

Where, S (J', J) = e22||U (2) ||2 + Ω4||U (4) ||2 + Ω6||U (6) ||2] The fluorescence branching ratio for the transitions originating from a specific initial manifold |4fN (S', L') J'> to a final many fold|4fN (S, L) J > is given by

Where, the sum is over all terminal manifolds.
The radiative life time is given by

Where, the sum is over all possible terminal manifolds. The stimulated emission cross -section for a transition from an initial manifold |4f N (S', L') J'> to a final manifold │4fN (S, L) J >| is expressed as

Where,λp the peak fluorescence wavelength of the emission band and Δλeff is the effective fluorescence line width.

3.4 Nephelauxetic Ratio (β) and Bonding Parameter (b1/2)

The nature of the R-O bond is known by the Nephelauxetic Ratio (β') and Bonding Parameter (b1/2), which are computed by using following formulae20,21. The Nephelauxetic Ratio is given by

where, νg and νa refer to the energies of the corresponding transition in the glass and free ion,respectively. The values of bonding parameter (b1/2) is given by

4. RESULT AND DISCUSSION

4.1 XRD Measurement

Figure 1 presents the XRD pattern of the sample contain - B2O3 which is show no sharp Bragg's peak, but only a broad diffuse hump around low angle region. This is the clear indication of amorphous nature within the resolution limit of XRD instrument.

Fig. 1: X-ray diffraction pattern of Bi2O3: Li2O: ZnO: B2O3: Eu2O3

4.2 Thermal Property

Figure 2, shows the thermal properties of ZnLiBiB glass from 3000C to 10000C. From the DSC curve of present glasses system, we can find out that no crystallization peak is apparent and the glass transition temperature Tg are 350,451 and 580 respectively. The Tg increase with the contents of Eu2O3 increase. We could conclude that thermal properties of the ZnLiBiB glass are good for fiber drawing from the analysis of DSC curve.

Fig.2: DSC curve of ZnLiBiB (EU) glasses.

4.3 Absorption Spectrum

The absorption spectra of Eu3+ doped ZnLiBiB(EU 01) glass specimen has been presented in Figure 3 in terms of optical density versus wavelength (nm). Four absorption bands have been observed from the ground state 7F0 to excited states 5D2,5L6,5G2 and (5G6,5G4) for Eu3+doped ZnLiBiB glasses.

Fig.3: Absorption spectrum of Eu3+doped ZnLiBiB (01) glass

The experimental and calculated oscillator strengths for Eu3+ions in zinc lithium bismuth borate glasses are given in Table 2.

Table2: Measured and calculated oscillator strength (Pm×10+6) of Eu3+ions in ZnLiBiB glasses.


Energy level from 7F0 Glass   Glass   Glass  
  ZnLiBiB(EU01)   ZnLiBiB(EU1.5)   ZnLiBiB(EU02)  
  Pexp. Pcal. Pexp. Pcal. Pexp. Pcal.
5D2 1.64 1.36 1.60 1.33 1.56 1.31
5L6 3.20 3.16 3.14 3.11 3.08 3.00
5G2 0.48 0.38 0.42 0.40 0.40 0.38
5G6,5G4 0.50 0. 40 0.44 0.41 0.41

0.39

r.m.s. deviation ±0.320   ±0.311   ±0.300  

The small value of r.m.s. deviation indicates fairness of fitting between experimental and calculated oscillator strengths.
Computed values of F2, Lande' parameter (ξ4f), Nephlauxetic ratio (β') and bonding parameter(b1/2) for Eu3+doped ZnLiBiB glass specimen are given in Table 3.

Table 3. F2, ξ4f, β' and b1/2 parameters for Europium doped glass specimen.

Glass Specimen F2 ζ4f β' b1/2
Eu3+ 372.63 1445.73 0.9645 0.1332

In the present case the three Ωλ parameters follow the trend Ω2> Ω4> Ω6. The spectroscopic quality factor (Ω4 /Ω6) related with the rigidity of the glass system has been found to lie between 1.346 and 2.200 in the present glasses.

The value of Judd-Ofelt intensity parameters are given in Table 4

Table4: Judd-Ofelt intensity parameters for Eu3+ doped ZnLiBiB glass specimens

Glass Specimen Ω2(pm2) Ω4(pm2) Ω6(pm2) Ω46 Trend References
ZnLiBiB(EU01) 2.499 2.297 1.707 1.346 Ω246 P.W.
ZnLiBiB(EU1.5) 2.495 2.414 1.689 1.429 Ω246 P.W.
ZnLiBiB(EU02) 2.511 2.420 1.100 2.200 Ω246 P.W.
ZBN1 3.15 1.57 1.53 1.03 Ω246 [22]
ZBN2 3.32 2.55 2.32 1.10 Ω246 [22]
FPG1 6.83 3.14 1.60 1.96 Ω246 [23]
BPB1 5.014 1.546 1.337 1.156 Ω246 [24]
BPB2 4.810 1.441 1.177 1.224 Ω246 [24]

From Table 4 it is observed that Ω2 parameter is high. The Ω2 parameter depends generally on the asymmetry of the sites in the neighborhood of rare earth ion. The higher the Ω2 parameter the higher is the degree of asymmetry around the rare earth ion and stronger the covalency of rare earth ion-oxygen bond.

4.4. Fluorescence Spectrum

The fluorescence spectrum of Eu3+doped in zinc lithium bismuth borate glass is shown in Figure 4. There are two broad bands observed in the Fluorescence spectrum of Eu3+doped 403 zinc lithium bismuth borate glass. The wavelengths of these bands along with their assignments are given in Table 5. Fig. (4).Shows the fluorescence spectrum with two peaks (5D0->7F2) and (5D0->7F5), for glass specimens.

Fig.4: fluorescence spectrum of Eu3+doped ZnLiBiB (01) glass

Table5. Emission peak wave lengths (λmax),radiative transition probability (Arad),branching ratio (β),stimulated emission cross-section( σp) and radiative life time( τR ) for various transitions in Eu3+doped ZnLiBiB glasses

Tran-   ZnLiBiB EU 01   ZnLiBiB EU 1.5     ZnLiBiB EU 02
sition λmax Arad β σp(10-20   Arad(s-1) β σ(10- τR(μs) Arad β σp  
  (nm) (s-1)   cm2) τR(μs)     20 cm2)   (s-1)   (10-20 τR(μs)
                        cm2  
5D0->7F2 619 30.203 0.220 0.01306   30.19 0.2121 0.0126   30.51 0.2130 0.012  
5D0->7F2 700 106.61 0.7793 0.05 7309.1 112.15 0.77 0.0561 702.5 112.2 0.769 0.0557 6975.5

Conclusion

In the present study, the glass samples of composition (25-x) Bi2O3:20Li2O:20ZnO: 35 B2O3: x Eu2O3 (where x=1, 1.5, 2mol %) have been prepared by melt-quenching method. The Judd-Ofelt theory has been applied to calculate the oscillator strength and intensity parameters Ωλ(λ=2, 4, 6). The radiative transition rate and the branching ratio are highest for (5D0->7F5) transition and hence it is useful for laser action. The stimulated emission cross section (σp) value is also very high for the transition (5D0->7F5). This shows that (5D0->7F5) transition is most probable transition.

References

  1. Wagh, A., Ajithkumar, M.P. and Kamath, S.D. Composition dependent structural and thermal properties of Sm2O3 doped zinc fluoro borate glasses, Energy Research J.4, 52 (2013).
  2. Som,T. and Karmakar,B. Infrared-to-Red Upconversion Luminescence in Samarium-Doped Antimony Glasses. J. of Luminescence, 12, 1989 (2008).
  3. Shen,L.F.,Chen,B.J.,Pun,Y.B. and Lin,H. Sm3+ doped alkaline earth borate glasses as UV-Visible photon conversion for solar cells. J. of Luminescence, 160, 138 (2015).
  4. Anjaiah, J. and Laxmikanth, C. Optical Properties of Neodymium Ion Doped Lithium Borate Glasses, 5,173 (2015).
  5. Bobkoval, N.M. and Khot, S.A. Zinc oxide in brate glass-forming systems. J. Glass and Ceramics, 62,170 (2005).
  6. Pal, M., Roy, B.and Pal, M. Structural characterization of borate glasses containing zinc and manganese oxide. J. Mod. Physics, 2, 1066 (2011).
  7. Reddy, M.B., Sailaja, S.,Girihar, P., Raju,C.N. and Reddy, B.S. Spectroscopic investigations of Sm3+ ions doped B2O3-Bi2O3-ZnO-Li2O glasses, Ferroelectric letters 38,50 (2011).
  8. Kumar, G.A., Martinez, A., Mejia, E. and Eden, C.G. Fluorescence and upconversion spectral studies of Ho3+ in alkali bismuth gallate glasses, J. Alloys. Comp.365, 120 (2004).
  9. Kam,C.H. and Buddhudu, S. Emission analysis of Eu3+: Bi2O3-B2O3-R2O(R=Li,Na,K) glasses, J. Quant. Spectrosc. Radiant Trans,87,337 (2004).
  10. Babu, P. and Jayasankar, C.K. Spectroscopy of Pr3+ Ions in Lithium Borate and Lithium Fluoroborate Glasses. Physica B: Condensed Matter, 301, 326 (2001).
  11. Gedam, R.S. and Ramteke,D.D. Electrical and optical properties of lithium borate glasses doped with Nd2O3, J. Rare Earths,30,789 (2012).
  12. Subhadra, M.and Kistaiah,P. Infrared and raman spectroscopic studies of alkali bismuth borate glasses: Evidence mixed alkali effect, Vibratinal Spectroscopy,62,27 (2012).
  13. Doualan, J.L., Girard,S.,Haquin,H.,Adam, J.L. and Montagne, J. Spectroscopic properties and laser emission of Tm3+ doped ZBLAN glass at 1.8 μm, Optical Materials, 24,577 (2003).
  14. Atul, D.,Sontakke, Tarafder, A., Biswas, K. and Annapurna, K. Sensitized red lumines-cence from Bi3+ co-doped Eu3+: ZnO-B2O3 glasses, Physica B, Elsevier. 404: 958 (2010).
  15. Gorller-Walrand, C. and Binnemans, K. Spectral Intensities of f-f Transition. In: Gshneidner Jr., K.A. and Eyring,L., Eds., Handbook on the Physics and Chemistry of Rare Earths, Vol. 25, Chap. 167, North-Holland, Amsterdam, 101-264 (1988).
  16. Sharma, Y.K., Surana, S.S.L. and Singh, R.K. Spectroscopic Investigations and Lumine-scence Spectra of Sm3+ Doped Soda Lime Silicate Glasses. J. Rare Earths, 27, 773-780 (2009).
  17. Judd, B.R. Optical Absorption Intensities of Rare Earth Ions. Physical Review, 127,761 (1962).
  18. Ofelt, G.S. Intensities of Crystal Spectra of Rare Earth Ions. J. Chemical Physics, 37, 511 (1962).
  19. Goublen, C.H. Methods of Statistical Analysis. Asian Publishing House, Bombay, Chap. 8, 138 (1964).
  20. Sinha, S.P. Systematics and properties of lanthanides, Reidel, Dordrecht (1983).
  21. Krupke, W.F. IEEE J.Quantum Electron QE,10,450 (1974).
  22. Pal,I., Agarwal, A.,Sanghi,S., Sanjay and Aggarwal, M.P.. Spectroscopic and radiative properties of Nd3+ ions doped zinc bismuth borate glasses. J. Pure and Appied Phy.51, 25 (2013).
  23. Babu,S., Balakrishna,A., Rajesh, D. and Ratnakaram ,Y.C. Dy3+ doped oxy-fluoride phosphate glasses for laser materials: A photoluminescence study. J. Chem Tech Research, 6, 3279 (2014).
  24. Kumar, M.V. and Marimuthu, K. Structural and luminescence properties of Dy3+ doped oxyfluoro-borophosphate glasses for lasing materials and white LEDs. J. Alloys and Compounds 629, 230–241 (2015).