Optical and structural investigation on sodium borosilicate glasses doped with Cr₂O₃

In this work, Sodium borosilicate glasses with chemical composition of 60% SiO₂-20% B₂O₃-20%Na₂O doped with different contents of Cr₂O₃ were prepared by melting-quenching method. Physical, structural and optical properties of glasses were investigated by studying density and molar volume, Fourier Transform Infrared (FT-IR) Spectra and UV-visible absorption spectroscopy. The results showed an increase in density of glasses with the increase of Cr₂O₃ that can be due to addition of oxide with high molar mass. The optical absorption spectra of un-doped glass reveals UV absorption due to trace iron impurities with no visible band however Cr₂O₃ doped glasses shows absorption in visible range that are characteristic. Increasing of Cr³⁺ ions in the glassy microstructure of samples provides a semiconducting character to Sodium borosilicate glass by reducing the direct and indirect optical band gaps of glass samples from 3.79 to 2.59 (ev) and 3.36 to 2.09 (ev), respectively. These changes could be attributed to the role of Cr³⁺ ions as the network former which asserts improvement of semiconducting behavior in presence of Cr₂O₃.