## "Investigations on Optical and Physical Properties of Sm2O3, Dy2O3 and Eu2O3 Doped Zinc Strontium Bismuth Borate Glasses"

Kothandan D1, Chandra Babu Naidu K2*, Jeevan Kumar R3*

1Sreenivasa Institute of Technology and Management Sciences, Chittoor, A.P, India

2Srinivasa Ramanujan Institute of Technology, Anantapuramu (A.P), India

3Department of Physics, S.K. University, Anantapuramu (A.P), India

*Corresponding authors: Chandra Babu Naidu K (2018) Srinivasa Ramanujan Institute of Technology, Anantapuramu (A.P), India. Tel: +919398426009; Email:

Jeevan Kumar R (2018) Department of Physics, S.K. University, Anantapuramu (A.P), India. Email: rjkskuphy@gmail.com

Received Date: 10 February, 2018; Accepted Date: 23 March, 2018; Published Date:  03 April, 2018

1.       Abstract

Borate glasses of stoichiometry (50-x) H3BO3-10SrF2-10Bi2O3-20ZnO-10SiO2-Mx (M = Sm2O3, Dy2O3 & Eu2O3, x= 0.01, 0.05, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5 & 3.0) are prepared by melt quenching method by doping various concentrations of rare earth metals (Sm, Dy and Eu). The resultants are characterized using X-ray diffract meter and UV-Visible spectrometer for investigating structural and optical properties respectively. The optical band gap energies (Eg) and refractive indices (n) are found to be varying between 3.39- 3.56 eV and 2.260-2.299. In order to identify the physical stability of glass samples physical properties have been studied. The density of glasses is decreasing with doping item and increasing with composition. In case of Sm3+ Dy3+ and Eu3+ doped glass, density are varying from 4.02-4.25 g/cm3, 3.89-4.13 g/cm3 & 3.64-3.89 g/cm3 respectively.  The motivation and novelty behind this study is to report the good dense as well as the physical stability of borate glasses.

2.       Keywords: Borate glasses; X-ray diffract meter; Physical Properties; Optical band gap; Melt quenching method

1.       Introduction

Borate glasses pertaining rare earth metal oxides have significant applications for solid state, luminescent applications, laser hosts, lamp phosphors, broad band amplifiers, sensors, optical data storage devices and optical fiber communication systems [1]. Kim et al. [2] investigated the luminescence property of rare earth doped bismuth borate glasses due to 4f-4f and 4f-4d electronic transitions in the visible light range. Padlyak et al. [3] also studied luminescence properties of the Samarium doped borate glasses by studying the optical absorption and photoluminescence spectra. Venkata Rao et al. [4] suggested that Dy3+ doped borate glasses are the candidate materials for yellow lighting applications in the visible range by studying optical properties. Shem et al. [5] demonstrated that Sm3+ doped alkaline earth borate glasses are well suited materials for UV to Visible photon conversion layer for solar cell applications. Ivankov et al. [6] revealed that the high content of Eu3+ has lead to the disappearance of broad band glass emission at the near UV range. Chimalawang et al. [7] investigated the physical properties of Dy+3 doped soda lime glass silicates. But to the best of author knowledge there is no detailed report on the optical and physical properties of Sm, Dy and Eu doped borate glasses. In this investigation an attempt has been made to study the optical properties of present glass materials.

2.       Experimental Procedure

The glasses of general formula (50-x) H3BO3-10SrF2-10Bi2O3-20ZnO-10SiO2-Mx (M = Sm2O3, Dy2O3 & Eu2O3, x= 0.01, 0.05, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5 & 3.0) have been prepared by mixing them in appropriate quantity with the help of digital electronic balance. The chemicals of 99.9 % purity (Sigma Aldrich) are taken. All these compositions are mixed together and stirred in a porcelain crucible. The mixture is melted by placing it in a programmable furnace 1100ºC for 30min. The glass samples are taken out from the furnace and pour onto different metal plates. The plate is again annealed for 300ºC and as the result the glasses are obtained having transparent, pure and amorphous in nature. The samples are characterized by using XRD (Bruker, Cu=15.418 nm) and UV-Visible spectrometer (UV-Visible-NIR JASCO spectrometer) for studying the structural, absorption spectra and optical band gap energies. Besides, the physical properties have been studied in order to identify the physical stability of glass samples.

3.       Result and Discussions

The recorded XRD profile of Sm3+, Dy3+ and Eu3+ doped zinc strontium bismuth borate glass (ZnSrBiB) as shown in Figure1 have confirmed the amorphous nature without exhibiting any single or polycrystalline phases.

3.1.  Optical Properties

The optical absorption spectra of (50-x) H3BO3-10SrF2-10Bi2O3-20ZnO-10SiO2-Mx (M = Sm2O3, Dy2O3 & Eu2O3, x= 0.01, 0.05, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5 & 3.0) is recorded and is shown in (Figure 1)

In the absorption spectra of present amorphous materials maximum absorption wavelength m) is observed and is tabulated in (Table 1).

While Dy-doped glass showed the absorption, peaks possessing the left shift over the wavelength range 750-1400nm. These absorption peaks may be due to the presence of few impurities. The diffuse reflectance spectra are recorded in wavelength range of 200-2500 nm in order to determine the optical band gaps for the glass samples. Using the following equation Kubelka- Munk function of reflectance F(R) can be calculated [8, 9].

_________________ (1)

The absorption coefficient α is directly proportional with F(R) and hence an equation for determining the band gap can be written as follows.

_________________ (2)

Where A= Energy- independent constant that depends on transition probability, Eg= optical band gap, n= the kind of transition i.e. n=2 for direct transition, 2/3 for direct forbidden transition, ½ for indirect allowed transition, 1/3 for indirect forbidden transition and hν = photon energy [8]. In the present study n = 2 is taken for direct transition. Eg values are determined and tabulated in table.1 by plotting (αhν)2 against the photon energy hν (eV) as shown in (figure 2) and the slope of α tends to zero. The obtained band gaps are found to be varying between 3.39- 3.56 eV. The refractive index (n) is calculated using the optical band gap energies (Eg) with the help of following formula.

_________________ (3)

In the present investigation for all the dopants of borate glasses the optical band gap energies are decreasing with increase of doping contents while refractive indices and absorbance (A) values are showing increasing trend with doping contents. This establishes a fact that there exists an inversely proportional relationship between Eg & n, A.

3.2.  Physical Properties

In respect of the physical properties refractive index (n), density (ρ), molar refractivity (Rm), concentration (mol/lit & ion/cm3), polaron radius (rP), intermolecular distance (d), field strength (F), molar volume (Vm), electric polarizability (α), reflection losses (dB) and metallization factors (Mf) are determined. These properties can show the mechanical stability of glass composition and are shown in (Table 2).

3.3.              Sm2O3 Doped Glass Matrix

These glasses in general are moisture insensitive and capable of accepting large concentration of rare earth ions without losing transparency. It is interesting to note that the increase in the Sm2O3 composition in the glass matrix enhances various optical parameters such as refractive index, polaron radius, inter-ionic distance, molar refractivity, electronic polarizability, dielectric constant and density [10]. Concentration and field strength values show the decreasing trend with increase of samarium content. The measured density, molar volume, refractive index and other related physical properties of Sm3+-doped ZnSrBiB glass samples for different Sm2O3 concentrations are shown in (Table 2) it is seen from the (Figure 6).

The density increases with an increase in samarium content. Since samarium has high relative molecular mass, therefore, it is an expected result. The change in molar volume depends on the rates of change of both density and molecular weight. However, the rate of increased molecular weight is greater than the rate of increase in density. This would be accompanied by molar volume, as can be seen from (Table 3).

The molar volume of the glass system increases with the increase in samarium content, which is attributed to the increase in the number of non-bridging oxygen (NBOs). It may be assumed that the increase in samarium content at the expense of SiO2 causes the opened glass network structure [11]. The variation of refractive index, polaron radius (rP) & field strength (F) of Sm3+ doped glass matrix is clearly shown in (Figure 4 &5) respectively

3.4.              Dy2O3 Doped Glass Matrix

It is interesting to note that the increase in the Dy2O3 composition in the glass matrix enhances various optical parameters such as refractive index, polaron radius, inter-ionic distance, molar refractivity, electronic polarizability, dielectric constant and density. Concentration and field strength values show the decreasing trend with increase of dysprosium content. From (Figure 7&9)

It has been found that the refractive index, dielectric constant and density values are increasing for all the glasses with the substitution of dysprosium oxide in the place of SiO2. Due to higher molecular weight of Dy2O3 compared to that of SiO2. Theoretically, the molar refraction, which depends on the refractive index, is a function of density and mean polarizability of the medium [12]. The variation of polaron ionic radius and field strength is shown in (Figure 8) and are following the similar trend as that of samarium doped glass matrix

The increase in the Eu2O3 composition in the glass matrix enhances various optical parameters such as refractive index, polaron radius, inter-ionic distance, molar refractivity, electronic polarizability, dielectric constant and density. Concentration and field strength values show the decreasing trend with increase of europium content. It is observed the (Table 4).

That the concentration increases with increasing Eu2O3 composition in the glass matrix. It should be mentioned that the europium ions are assumed to be uniformly distributed in the glass matrix. Also, observed from (Figure 11).

That the decrease of polaron radius with increasing Eu3+ content is most likely related to the increased value of ionic concentration (N) of europium. The RE (rare earth) ions are situated between the layers and thus the average RE– oxygen distance decrease. As a result of that, the Eu-O bond strength increase, producing a stronger field around the Eu3+ ions. The variation of refractive index and density is shown in (Figure 10 &12) respectively.

The current study pointed out a thing that the glass ceramic materials with good dense and physical stability like samarium doped borate glasses are well suited for potential optical transparent materials in bio processing and bio techniques. Therefore, these kinds of materials will have some attractive importance in optical transparent materials or glass slides which are being used in biomedical treatments. The present glass ceramics have showed good density and physical stability than the reported literature [1].

4.       Conclusions

The values of optical band gaps of the glass sample are due to direct transitions. Decreasing of Eg values confirms the extension of localized states into band gap. The observed variations in band gap are due to oxide ion polarizability and hence the structural changes may occur in the glass network with the replacement of rare earth oxides. Hence, these materials can act as glass network modifier (GNM). The decrease of band gap energy in turn causes to increase of refractive index with doping content. The density of glasses is decreasing with doping item and increasing with composition i.e. in case of Sm3+ Dy3+ and Eu3+ doped glass, density are varying from 4.02-4.25 g/cm3, 3.89-4.13 g/cm3 & 3.64-3.89 g/cm3 respectively. It is interesting to note that the increase in the rare earth doped composition in the glass matrix enhance various optical parameters such as refractive index, polaron radius, inter-ionic distance, molar refractivity, electronic polarizability, dielectric constant and density. The motivation and novelty behind this study is to report the good dense as well as the physical stability of borate glasses.

5.       Acknowledgements

Authors express their thanks to Department of Physics, Sri Krishnadevaraya University, Anantapuramu, for providing laboratory facilities to carry out the present research work. The financial support rendered by the UGC under SAP [No.F.530/8/DRS/2010 (SAP- I)] and Department of Science and Technology under FIST [SR/FST/PSI-116/2007], New Delhi, are gratefully acknowledged.

Figure 1: The XRD spectra Sm (1.0, 1.5, and 2.0) (b) Dy (1.0, 1.5, and 2.0) & (c) Eu (0.5, 1.0, and 1.5) doped glass matrix.

(Figure 2) (b) Reveals that at the high concentrations of Dy, λm decreases to 290 nm. On the other hand the rest compositions exhibit the identical λm values (301 nm).

Figure 2: Absorption spectra of (a) Sm (1.0, 1.5, and 2.0) (b) Dy (1.0, 1.5, and 2.0) & (c) Eu (0.5, 1.0, and 1.5) doped borate glasses.

But, interestingly (Figure 3) (c) shows for all contents of Eu doped borate glasses perform the similar λm values of 301 nm. Comparatively, Sm doped glass shows few absorption peaks between wavelength range 1100-1400 nm

Figure 3: (αhν)2 Vs photon energy plots of (a) Sm (1.0, 1.5, and 2.0) (b) Dy (1.0, 1.5, and 2.0) & (c) Eu (0.5, 1.0, and 1.5) doped borate glasses.

Figure 6: The refractive index of Sm3+ doped glass matrix.

Figure 4: The refractive index of Sm3+ doped glass matrix.

Figure 5: The variation of polaron radius (rP) & field strength (F) of Sm3+ doped glass matrix.

Figure 7:  The variation of reflection loss refractive index of Dy3+ doped glass matrix.

Figure 9: The variation of density and dielectric constant of Dy3+ doped glass matrix.

Figure 8: The variation of polaron radius (rP) & field strength (F) of Dy3+ doped glass matrix.3.

Figure 11: The variation of polaron radius (rP) & field strength (F) of Eu3+ doped glass matrix.

Figure 10: The refractive index of Eu3+ doped glass matrix.

Figure 12: The density of Eu3+ doped glass matrix.

 S.No Sample Eg (Ev) N Λm (Nm) A 1 Sm1.0 3.46 2.283 296 0.888 2 Sm1.5 3.42 2.292 301 1.761 3 Sm2.0 3.39 2.299 301 2.647 4 Dy1.0 3.56 2.26 301 0.882 5 Dy1.5 3.51 2.271 301 1.781 6 Dy2.0 3.51 2.271 290 2.667 7 Eu0.5 3.49 2.276 301 0.868 8 Eu1.0 3.48 2.278 301 1.761 9 Eu1.5 3.47 2.281 301 2.681

Table 1: Data for optical parameters of Sm, Dy & Eu doped borate glasses.

 Sm2O3 0.01 0.05 0.1 0.5 1 1.5 2 2.5 3 concentration(mol/lit) 0.00501 0.0335 0.06955 0.35431 0.70909 1.06801 1.41494 1.75491 2.0748 concentration(ion/cc) 3.29e+18 2.04e+19 4.22e+19 2.14e+20 4.27e+20 6.44e+20 8.53e+20 1.06e+21 1.25e+21 inter-molecular distance 5.74e-07 3.24e-07 2.49e-07 1.32e-07 9.72e-08 8.03e-08 7e-08 6.27e-08 25.4 molar volume 24.7611 24.7534 24.6137 24.8421 24.8971 24.9273 25.0383 25.1821 9.21653 molar refractivity 8.32318 8.38595 8.36496 8.48106 8.86139 8.94 9.00065 9.07725 6.52e-23 electric polarizability 1.7e-20 2.6e-21 1.8e-21 3.41e-22 1.85e-22 1.24e-22 9.64e-23 7.89e-23 5.36 reflection losses 4.65952 4.72723 4.75437 4.79513 5.17861 5.24763 5.27529 5.30297 5.35841 metallization factors 0.52326 0.52093 0.51999 0.5186 0.50573 0.50346 0.50256 0.50166 0.49985

Table 2: The data of physical parameters of Sm3+ doped glass matrix.

 Dy2O3 0.01 0.05 0.1 0.5 1 1.5 2 2.5 3 concentration(mol/lit) 0.00732 0.03581 0.07186 0.35662 0.7114 1.07032 1.41725 1.75722 2.07711 concentration(ion/cc) 4.41e+18 2.16e+19 4.33e+19 2.15e+20 4.28e+20 6.45e+20 8.54e+20 1.06e+21 1.25e+21 Inter-molecular distqance 6.1e-07 3.59e-07 2.85e-07 1.67e-07 1.33e-07 1.16e-07 1.05e-07 9.81e-08 9.28e-08 molar volume(g/cc) 27.9759 27.9682 27.8286 28.0569 28.0569 28.1421 28.2532 28.3969 28.6436 molar refractivity 9.3366 9.39937 9.37838 9.49448 9.87481 9.94924 10.0141 10.0907 10.23 electric polarizability 1.81e-20 3.72e-21 1.86e-21 3.76e-22 1.96e-22 1.31e-22 9.92e-23 8.02e-23 6.82e-23 metallization factors 0.66626 0.66393 0.663 0.6616 0.64873 0.64646 0.64556 0.64466 0.64285

Table 3: The data of physical parameters of Dy3+ doped glass matrix.

 Eu2O3 0.01 0.05 0.1 0.5 1 1.5 2 2.5 3 concentration(mole/lit) 0.00288 0.03137 0.06742 0.35218 0.70696 1.06588 1.41281 1.75278 2.07267 concentration(ion/cc) 3.17e+18 2.03e+19 4.2e+19 2.14e+20 4.27e+20 6.43e+20 8.52e+20 1.06e+21 1.25e+21 inter-molecular distance 5.23e-07 2.72e-07 1.98e-07 8.01e-08 4.57e-08 2.89e-08 1.85e-08 1.12e-08 5.9e-09 molar volume(g/cc) 22.2822 22.2745 22.1348 22.3632 22.4182 22.4484 22.5594 22.7032 22.9499 molar refractivity 8.07422 8.13699 8.116 8.2321 8.61243 8.68686 8.75169 8.82829 8.96757 electric polarizability 1.59e-20 2.43e-21 1.69e-21 3.12e-22 1.7e-22 1.12e-22 9.26e-23 7.66e-23 6.33e-23 reflection losses 4.44502 4.51273 4.53987 4.58063 4.96411 5.03313 5.06079 5.08847 5.14391 metallization factors 0.39876 0.39643 0.39549 0.3941 0.3941 0.37896 0.37806 0.37716 0.37535

Table 4: The data of physical parameters of Eu3+ doped glass matrix.

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Citation: Kothandan D, Chandra Babu Naidu K, Jeevan Kumar R (2018) Investigations on Optical and Physical Properties of Sm2O3, Dy2O3 and Eu2O3 Doped Zinc Strontium Bismuth Borate Glasses. Int Bioprocess Biotech. IJBBT-102. DOI: 10.29011/IJBBT-102.100002