Optical Investigation and Electronic Polarizability of Nd³⁺ Doped Soda-Lime-Silicate Glasses

Abstract

Problem statement: This study researched on different physical and optical properties of Nd³⁺ doped soda-lime-silicate glass. The glasses containing Nd³⁺ in (65-x)SiO₂: 25Na₂O: 10CaO: xNd₂O₃ (where x = 0.0-5.0 mol%) had been prepared by melt-quenching method. The density and molar volume increase with increasing of Nd₂O₃ concentration due to increasing of Non Bridging Oxygen (NBOs) in glass matrix. The optical spectra were measured and evaluated their optical band gap and found to decrease with increasing of Nd₂O₃ concentration. Moreover, these results showed that the refractive index of glass does not only depend on the density but also depend on the electronic polarizability of the glass. The values of polarizability of oxide ions, theoretical optical basicity were also determined. Approach: This study investigated the effect of Nd₂O₃ content on optical band gap, density, molar volume, optical basicity and polarizability in soda-lime silicate glass. Series of Nd³⁺ doped soda-lime silicate glasses (in mol%): (65-x)SiO₂-25Na₂O-10CaO-xNd₂O₃ (x = 1-5 mol%) were prepared by the normal melt-quenching technique. Analytical reagent grade chemicals of SiO₂, Na₂O, CaO and Nd₂O₃ were used in the glasses preparation. Each batch of chemical was powdered finely and mixed thoroughly in porcelain crucibles and was later melted in an electrical muffle furnace for 3 h, at 1200°C. After complete melting, the homogenized melt was quickly poured onto a stainless steel mould that was heated at 500°C to form the glasses. The glass blocks thus resulted were immediately transferred to the annealing furnace that and were annealed at 500°C for 3 h and then slowly cooled down to the room temperature in order to remove possible thermal stains in the glasses. Finally, the as-prepared glass samples were cut and then finely polished to a thickness of 3 mm. The glass densities were measured by using xylene as an immersion liquid based on the Archimedes's principle. Glass refractive indices were measured at room temperature using an Abbe refractometer (ATAGO) and mono-bromonaphthalene as an adhesive coating. The optical absorption spectra of Nd³⁺ doped soda-lime silicate glasses were recorded at room temperature using a UV-VIS spectrophotometer (Hitachi, U-1800), working in 300-700 nm. Results: By addition of Nd₂O₃ into the SiO₂-Na₂O-CaO glass network, the density increases with increase in Nd₂O₃ content. The molar volume of the glass systems under study increases with increase in Nd₂O₃ content, which is attributed to increase in the number of Non Bridging Oxygen (NBOs). The optical band gap slightly decreases with the increase of Nd₂O₃ and results in the increase of bonding defect and non-bridging oxygen. The optical basicity of the glasses are increasing with Nd₂O₃ content change with the increasing of polarizability and consequently the increase in refractive index. Conclusion: The study of SiO₂-Na₂O-10CaO-Nd₂O₃ glass systems showed that the density and refractive index increase with increasing concentration of Nd₂O₃. The increase of molar volume with Nd₂O₃ content indicates that the extension of glass network is due to the increase of the number of NBOs. The optical band gap slightly decreases with in Nd₂O₃ content due to an increase in the degree of localization of electrons thereby increase of the donor center in the glass matrix. The electronic polarizability and optical basicity increase with the increase of mol% of Nd₂O₃, which is in agreement with the decrease of optical band gap. Moreover, the results found in this study show that the refractive index of glass does not only depend on the density but also depend on the electronic polarizability of the glass.