Effect of Bi2O3 on structural and optical properties of Li2O·PbO·Bi2O3·B2O3 glasses

The quaternary glass system has a composition of 30Li2O·20PbO·xBi2O3·(50-x)B2O3 (where x = 0, 10, 20, 30, and 40 mol%) was fabricated by using the melt quench technique at the temperature 1100 °C. The broad haloes obtained by the XRD diffractograms confirm the amorphous nature of the samples. Density, molar volume, and crystalline volume were found to be increased depending on Bi2O3 concentration. Structural properties were studied with the help of FTIR spectroscopy in the range of 400–2000 cm−1. The analysis of IR spectra reveals the presence of octahedral [BiO6], [BO4], [PbO4], and tetrahedral [BiO3], [BO3] structural units in the present glasses. Increases in bismuth concentration result in the transformation of [BO3] structural units to [BO4] structural units. The presence of a sharp cutoff and broad transmission region make these glasses suitable for spectral devices. The cutoff wavelength, optical band gap, and Urbach’s energy were estimated using UV absorption spectra. The increase in cutoff wavelength and decrease in band gap with bismuth content can be associated with the rise in non-bridging oxygens. Urbach’s energy values revealed that the defect concentration could be controlled by the presence of Bi2O3 content in the present glass system. The values of optical parameters, viz., refractive index, molar refractivity, molar polarizability, electronic polarizability, optical basicity, and theoretical optical basicity, increase with Bi2O3 content. The high values of refractive index and low metallization criterion indicate that the studied glass system may be potentially used for non-linear optical applications.