Spectroscopic Properties of Alumina Borosilicate Glassesw Alkaline Oxides Doped with Sm2O3 for Display Laser Emission

This research investigates the influence of the concentration of Sm +3 ions on the features of a new borosilicate glass system with the composition 50B 2 O 3 – 14SiO 2 - 20Li 2 O – 15Na 2 O – 1.0Al 2 O 3 -x(Sm 2 O 3 ), where x= 100, 200, 300, 400, and 500 ppm. The glasses are characterized by XRD, FTIR, UV- Vis- NIR, and photoluminescence spectra. The XRD results proved that all prepared glass has amorphous nature. Moreover, it was found that the value of density,  , and refractive index,n, increase with increasing of Sm +3 content. Otherwise, the value of molar volume, optical energy gap, and boron-boron distance decrease by increasing sm +3 concentration. The structure of glasses studied was investigated by computing 𝐼𝑛𝑡𝑒𝑟𝑛𝑢𝑐𝑙𝑒𝑎𝑟 ( 𝑟 𝑖 ) , Polaron radius (𝑟 𝑝 ) , field strength ( 𝐹 ) and the deconvolution of FTIR spectra. Judd-Ofelt theory applied to clarify the structural changes and nature of the bonds of prepared glasses. Moreover, A spectroscopic quality factor, the b ranching ratio (βr) , and lifetime (τ) are calculated via the parameters of Judd-Ofelt. The color chromaticity of the present glasses evidenced that the emission was in the white-reddish orange region under 402nm excitation depended on the concentration of Sm 3+ ions incorporated into the host glasses. From photoluminescence emission, stimulated emission cross-section, and CIE chromaticity leads to these glasses are promising for light-emitting diode (LED) as; laser material in a wide range.


Introduction
Borosilicate glass has attracted the researcher's attention due to its superior properties compared to ordinary glass. It has a very week thermal expansion coefficient equals to~3 × 10 −6 K −1 at 20 °C [1] such glass doesn't suffer from thermal shock. It can be used in reflecting telescope manufacturing. [2] Also, this glass helps to fabricate precise lenses. Borosilicate glass has a vital contribution to immobilizing and disposal of radioactive waste because it is distinguished by its chemical resistance. [3] Borosilicate glass consists of different oxides such as B2O3, SiO2, Na2O, Li2O, and AL2O3. The mainly former of borosilicate glass is B2O3.
Glass which is containing borates has special attention because of its promising linear and nonlinear optical properties [4] . The increase of B2O3 content enhances chemical resistance and improves transparency. Since borate glasses own high phonon energies which may hold back the efficiency of their luminescence during various relaxations [5] The addition of silica to borate glass reduces the thermal expansion coefficient and enhances the melting point and the working point. The acid stability of the glass decreases as the silica concentration decreases. Another component of borosilicate glass is Alkali metal oxide. It cooperates with silica to reduce the melting temperature and enhancement of low thermal expansion. [6] Alkali Metal oxide has an important role in the crystallization process, combining two metal oxide enhanced the resistance toward unwanted crystallization. [7] Therefore, alkaline earth cations can be added to the borate glass to upgrade their optical properties, impact the network connectivity, arranging of modifier cations and modify chain bonding in glasses by replacing the bridging oxygen with non-bridging oxygen [5] . Li + ions improve the acid-resistance of glass by forming bonds with glass networks [7] . Other oxides such as aluminum trioxide as a modifier of glass (Al2O3), have an important role in the fluidity of the glass as increasing of alumina decreasing the fluidity of glass [7] . Alumina also enhances the temperature of glass processing [8] , enhancing the glasses' stability [9] , affect the lasing and thermo-mechanical properties of the products in which they have been associated [9] . Interestingly, borate glasses act as suitable host materials for exploring both the nature and structure of the luminescence and paramagnetic centers [10] .In the recent three decades, doped materials with trivalent rare earth (RE 3+ ) ions are extensively used for the upgrading of several optical devices, e.g. waveguides, up-conversion lasers, optical fibers, detection of infrared radiation, optical amplifiers, display devices, sensors, and light converters. [11][12] . The optically active f-f electronic transitions of lanthanides ions generate sharp emission lines when integrated into different glass matrices  . Owing to high thermal stability, promising optical, structural, and electrical properties low melting point, good RE 3+ ion solubility, and high transparency, [11] . The importance of Glass containing Sm +3 is delivered from its visible emissions through different channels of emission [9] . The luminescence spectrum of Sm +3 ions in glasses and crystals shows distinct green, orange, and red emission bands, which refer to the 4 G5/2 6 H5/2, 4 G5/2 6 H7/2, and 4 G5/2 6 H9/2 emission transitions, respectively that can be used in fluorescent display devices, visible lasers, new light sources, and UV sensor [10] . In this work, borosilicate glass which was doped with Sm 3+ has been prepared with the chemical formula (50B2O3-14SiO2-20Li2O-15Na2O-1Al2O3-xSm2O3), where x= 100, 200, 300, 400, and 500 ppm. The objectives of this work are (i) To synthesis borosilicate glasses doped with Sm 3+ with different concentration of Sm2O3 by usual melt quenching technique, (ii) To characterize the glass samples by XRD, FTIR, UV, and PL, (iii) To compute and measure the optical and physical parameters with different concentration of Sm2O3. (iv) To investigate optical properties which include the absorption and luminescence spectra. By the use of emission spectra of Sm 3+ ions the color coordinates were evaluated and were presented in the CIE color diagram.

Experimental
The glass samples with composition of 50B2O3-14SiO2-20Li2O-15Na2O- Sm2O3, sample code (BSLNA2), 50B2O3-14SiO2-20Li2O-15Na2O-1.0Al2O3-300ppm Sm2O3, sample code (BSLNA3), 50B2O3-14SiO2-20Li2O-15Na2O-1.0Al2O3-400ppm Sm2O3, sample code (BSLNA4) and 50B2O3-14SiO2-20Li2O-15Na2O-1.0Al2O3-500ppm Sm2O3, sample code (BSLNA5). These glasses were synthesized and prepared by standard melt quenching technique. High-quality powders of lithium carbonate Li2CO3 (99.5%, EUROMEDEX), sodium carbonate Na2CO3 (99%, Chemajet), boric acid H3BO3 (99.98%, Sigma-Aldrich), acid-washed quartz sands SiO2 (99.9 %, Sigma-Aldrich), aluminum oxide Al2O3 (99%, Sigma-Aldrich ) and Samarium Oxide Sm2O3 (purity 99.9%, Sigma-Aldrich) were weighed by using a digital balance and mixed well, then charged into platinum crucible followed by melting in an electric furnace at 1050 o C for 20 minutes. Then we poured melts onto a steel plate and annealed them in a furnace at 600 °C for 3 hr to get rid of the thermal strains. The prepared glasses are named BSLNA0, BSLNA1, BSLNA2, BSLNA3, BSLNA4, and BSLNA5, respectively as found in Table 1. XRD was carried out to investigate the amorphous network of the prepared glass samples. BRUKER X-Ray Powder Diffraction system was used in this test. The range of investigation was ( 0-100) 2 θ with a radiation source of Cu (λ=1.5406°A). An optical glass surface was obtained after polishing each sample surface with fine Al2O3 powder. The thickness of each sample was measured by a micrometer. Then the UV-vis-NIR absorption spectra were measured in the range of 200-2500 nm at ambient condition by spectrophotometer JASCO Corp, v-570, Rel-00 Japan with the double beam. The Photoluminescence spectra were recorded by using fluorescence spectrometer Ls 55 Perkin Elmer in the range of 300-900 nm at room temperature. FTIR was used to study the structural changes of each sample of glass after doping with different concentrations of Sm2O3. FTIR measurement in the range of 350-4000 cm −1 was occurred by BX Perkin Elmer equipment using KBr pellets. Figure 1 demonstrates the XRD data of the prepared glass sample from BSLNA0 to BSLNA5. The XRD data confirmed the amorphous nature of glass by exhibiting broad diffused peaks. Moreover, no significant sharp peaks appeared in the data and the atoms of glass showed random distribution in the glass network, furthermore large variation in interatomic distances [9] .

Results and Discussion
The corresponding glass samples density were measured at ambient condition via Archimedes concept. The density of glass calculated by using Eq. [1], ρ = − • ( g/cm 3 ) [13] [1] Where, ρ, is a glass sample density (g/cm 3 ), Wair is the weight of prepared glass in the air, W liquid is the weight of glass in toluene and ρliquid is a density of toluene (0.864 g/cm 3 ). The molar volume of glass samples was obtained by implementing the Eq. [2], V m = (cm 3 /mol) [13] [2] Since Vm is the molar volume of the glass sample (cm 3  • 1000 (g. atom/L ) [13] [4] Since, C, is the oxygen atoms number which is existing in the structure of each glass sample.
As found in Table 2, the density of glass samples was enhanced from 2.397 to 2.625 g/cm 3 by increasing the Sm2O3 concentration from 0 to 500 ppm. The increase in density as a result of increasing OPD from 78.3 to 85.61 g.atom/L. Thus, the glass samples become denser and more compact [14] , another factor that increased the density of glass samples is the alteration of [BO3] -3 triangles into [BO4] -4 tetrahedral by the gradual increase of Sm 3+ ions in glass samples. [15] As a result of Sm2O3 concentration increasing in glass sample, the molar volume decreased from 27.58 to 25.24 (cm 3 /mol), we ascribed this observation due to the decrease which occurs for both interatomic distances and the length of bonds between doped glass atoms. Such results enhanced the compactness of the structure. [9] The average boron-boron separation is also calculated by Eq. 5 to clarify the effect of modifier concentration on the glass system.
Where and XB is molar volume and mole fraction of B2O3 respectively.
In the present work, by increasing Sm2O3 concentration, the boron-boron separation, 〈 − 〉 , value decreased as shown in Table 2. Noticeably, the previous results confirmed that, by increasing the concentration of Sm2O3, the molar volume and the interatomic spacing decrease which enhanced the compactness of glass. [9] .
The value of indirect optical band gap, , of prepared glasses can be calculated from the following Eq. [6] [20] .
Where, α(v), is the optical absorption coefficient [22] . By employing the Eq. [7] absorption coefficient (α ) can be calculated by Eq. [7]. [12] α (υ) The thickness of the glass samples is t and the intensity of incident light is I0, while the intensity of transmitted light is It. Light energy is hν, α0 is an energy-independent constant, m= 2 for the allowed indirect transition. Tauc's plot is shown in Fig 3. for indirectly allowed transitions. can be determined by deriving a linear portion of the curve to the Xaxis at Yaxis= 0. The values are monitored and found in Table 3. As is evident, , values were reduced from 3.61 to 2.0 eV by increasing Sm2O3 concentration from 0 to 500ppm [20] .
The physical parameters such as; ri, rp, F, n, Rm, and m confirm the glass structure which is determined by the following Eq.
As is clear of calculated values, ri and,rp ,values reduce with increasing Sm 3+ ions.
Consequently, the strength of the Sm-O bond increases, so the field strength (F) around Sm 3+ ions becomes stronger. The combining between these obtained values and the density results confirms the compactness of glass structure with addition Sm 3+ ions consequently, decreasing in the degree of delocalization of electrons occurs, due to increase in the compactness of glass and then increases the donor centers in the glass matrix and as a result, optical energy band gap decreases. [ 20] The refractive index, n, is one of the most significant properties in optical glasses [21] . The refractive index values of prepared glass samples were calculated by using Dimitrov and Sakka relation as shown in equation [13] [22] and obtained in Table 5.
The,n, value increases from 2.2497 to 2.736 with the concentration of Sm 3+ ions increase from 0 to 500ppm in prepared glasses. The value of n depends on ion polarization, electron density, and molar masses. The improvement in the refractive index is due to strong polarizable nonbridging oxygen (NBOs) generation in the glass network. Non-bridging oxygen formation provides greater polarizability over the covalent oxygen bridging bonds by providing a higher refractive index.
The nonlinear response of the materials depends on polarizability. The electronic polarization of the materials causes the optical non-linearity upon exposure to intense light beams [22] .
Polarizability is correlated to physical and chemical properties such as optical UV absorption of metal ions and electro-optical effect [23] . The molar refraction is proportionate to molar polarizability, which is associated with the glass sample structure.
Molar refraction (Rm, cm 3 mol −1 ) is calculated by applying the following Lorentz-Lorenz Eq. 14: = The values of polarizability (αm) and molar refraction (Rm) for samarium doped glass samples are listed in Table 3. Also the dielectric constant (ε) and refraction loss (RL) is computed by employing the following equations: [33] = 2 The increase in the, Rm, m,  and RL be attributed to the increase of the (NBO) in the glasses network structure with increasing Sm 3+ ions.
Judd-Ofelt concept has been used to get more information about glass structure and also depends on host material [13] .  [18] where m and e are the electron's mass and charge, respectively. N is Avogadro's constant, c is light velocity, the molar absorptivity (cm −1 ) is symbolized by ε(υ), and ∫ ε(υ) dυ is the part which is located under the curve of absorption. Fcal was determined from the Eq. [19] [13] F cal = 8 π 2 mcυ 3h (2J+1) (n 2 +2) 2 9n * ∑ Ω λ (ɸJ ‖U λ ‖ ɸ ′ J ′ ) 2 λ=2,4,6 [19] where m is the electron mass, the wavenumber (cm −1 ) is symbolized by υ, c is light velocity, h is Plank's constant, the refractive index is symbolized by n, the Lorentz local electric field correction is equal (n 2 +2) 2 /9n, Judd-Ofelt parameters are symbolized by Ωλ where (λ=2, 4, 6), the ground state angular momentum is symbolized by J, the excited state is symbolized by ɸ ^'J′, the ground state is symbolized by ɸJ, and ‖U λ ‖ 2 refers to squared doubly reduced matrix elements of the tensor operator. Parameters of Judd-Ofelt are significant to know more around rare earth environments, the Internal structure of glass, the nature of bonds and tell us more about the relation between Sm 3+ ions and the host material [13] . Ω2 symbolizes changes in internal structure, the nature of bonds, asymmetric, and covalent bonds between rare earth ions and surrounding ligands [13] . Ω4 and Ω6 related to the rigidity and viscosity of prepared glass [13] . The higher values of Ω4 and Ω6 in our glass system confirm the high rigidity and high viscosity of this glass [13] . By calculating the ratio between Ω4 and Ω6 parameters the spectroscopic quality factor X will be obtained, which tells us about the quality of prepared glass samples. In our glass system X-factor (> 1) confirms the high quality and stability of this glass, therefore, it can be used in optical devices development [13] . It is observed from has been observed in the reported Sm +3 doped borate glasses [11] . In the two upper cases, the higher magnitudes of Ω4 confirm the high rigidity of prepared glass samples [13] . Lower magnitudes of Ω2 are due to distortion that results from the change in structure due to the large size of modifier and strong Sm-O bond [13] which confirmed the high degree of symmetry and strength of ionic bond nature around the Sm 3+ ions [13 . Also, we calculated the root mean square (r.m.s) by equation [20]. To estimate the quality of the fit between the two oscillator strengths fcal and fexp.  [20] Where p is the number of observed transitions on the absorption spectrum.
The lower values of r.m.s. Is evidence that fitting quality Table (5). Branching ratio describes the probability of stimulated emission for a specific transition, it is a significant factor in laser manufacturer and it has been used to predict the intensities of radiative emission lines that result from an excited state [13] . βr is calculated from the equation [21] [13] β r = A Rad A T [21] Where ARad is the probability of transitions from excited bJ′ to lower state aJ for electric dipole spontaneous emission and it is obtained from Eq. [22], AT symbolizes to total possibilities of all transitions. The transition which βr≥0.50 is extra distinct for laser radiation [13] . From table 8, it is observed that 6 H5/2→ 6 F1/2 emission, shows the highest values of branching ratio (βr≥0.50) so, it can be used for a laser manufacturer. Radiative lifetime τ is not affected by phonon energy of the host matrix but it primarily depends on the total probability of spontaneous transition [13] .
The measuring of the emission spectra of prepared glass at started by indicating the excitation wavelength 402nm as shown in Figure.7. The spectra of emission of Sm 3+ doped BSLNA glass show three important peaks centered at 562, 600, and 647 nm, due to transition from 4 G5/2→ 6 H5/2, 6 H7/2, and 6 H9/2 transitions of Sm 3+ ions, respectively [12,27] . The emission line centered at 600 nm ( 4 G5/2→ 6 H7/2) is the highest intense from all BSLNA glasses doped with Sm 3+ ions which give orange emission [12] and 4 G5/2-6 H9/2 (647nm) transition gives red emission [12] and shows moderate intensity, the transition at 562 nm 4 G5/2→ 6 H5/2 shows the lowest intensity between the other two transitions. The glass containing Sm2O3 emits bright reddish-orange emission due to the obvious emissions at 562 ( 4 G5/2→ 6 H5/2), 600 ( 4 G5/2→ 6 H7/2), and 647 ( 4 G5/2→ 6 H9/2) nm. As is evident in Figure. 7 the peak intensities enhanced with the increase of Sm2O3 concentration from 100 to 400 ppm then the peak intensities decrease at Sm2O3= 500ppm. This observable fact is called luminescence quenching. With increasing concentration of Sm2O3 the glass matrix becomes crowded by Sm 3+ ions this reduces the Internuclear distance (ri) between Sm 3+ -Sm 3+ ions also the distance between donor and acceptor centers decreases significantly [5] . Consequently, the excitation energy could be transferred from Sm 3+ ion to another ion by the interaction between two active ions so the intensity of luminescence decreases [9,31] . The luminescence intensity of the emission spectral measurements of the prepared glasses has been obtained using 1931 CIE chromaticity diagram. The CIE chromaticity coordinates are found in the range whitereddish-orange range, it is dependent on the concentration of Sm3+ ions in the host glass matrix (see Fig. 8).
FTIR spectroscopy is a precious technique to study different functional groups in the glass network structure. FTIR absorption spectra of the prepared glass samples were recorded in the wavenumber range from 400 cm -1 to 3600 cm -1 at ambient conditions and depicted in Figure.3.a. Deconvolution was applied on FTIR spectra, fourteen characteristic bands were indicated. These bands belonged to functional groups presented in the glass system as illustrated in Fig. (3.b). Table 3 includes the peak positions and their assignments. The peak in the wavenumber range of 415-422 cm -1 is ascribed to Li2O [13,16] . The peak of 432-444 cm -peak in the wavenumber range of 650-663cm -1 is attributed to asymmetrical bending vibrations (υ4) of Si-O-Si [12] . The peak in the range of 704-712 cm -1 is due to the bending vibration of [BO3] units [12,[17][18][19]22] . The peak in the wavenumber range of 850-870 cm -1 is due to stretching vibrations of tri-, tetra-, and penta borate groups [20] . The peak which is lied between 931-955 cm -1 is attributed to B-O stretch in BO4 units from di-borate groups [12] . The peak which is between 1033-1045 cm -1 is due to Sm 3+ stretching vibration [23] The peak which is between 1070-1115 cm -1 is due to the symmetric stretching vibration of Si-O-Si bonds [12] . The peak in the range of 1330-1345 cm -1 is attributed to B -O stretch in BO3 units from varied types of borate groups [12] . The peak in the range of 1414-1426 cm -1 is attributed to B-O stretching vibration of BO3 units in metaborate, pyroborate& orthoborate groups [12] .
The peak in the range of 1535-1549 cm -1 is due to stretching modes of Si-OH and B-O stretch in BO4 units from tetrahedral groups [24] . The peak in the range of 1650-1660cm -1 is due to the BObond in the isolated pyroborate group [12] . The peak of Al + wasn't indicated in IR absorbance spectra as shown in Fig.1, because the concentration of Al 3+ was scanty and its signal of vibration frequency was very weak [18] . The groups like di, tri, Penta, meta, and boroxol rings with bridging or non-bridging oxygen ions participate in the formation of multicomponent borosilicate glasses [25] . In the glass network, the area below the curve of BO4 and units [25] , also the peak lies in 1426 cm -1 shifted to 1414 cm -1 . This shifting to lower wavenumber clarifies that the phonon energy of the glass system decreased because it depends on BO3 units [26] which enhanced the efficiency of fluorescence [26] .

CONCLUSION
From the results which were obtained in the present studies, it can be concluded that; The glass samples of composition (50B2O3-14SiO2-20Li2O-15Na2O-Al2O3-xSm2O3), where       Compositions (mol%) and shapes of our prepared glasses system (50B : Table (1) ).
Glass code Chemical composition Samples shape xygen packing and o , /mol) 3 ), molar volume (cm 3 The values of the density (g/cm : Table (2) density (g.atom/L) of the prepared glass samples.