Physical and spectroscopic studies of CaF2-Al2O3-Bi2O3-B2O3-CuO glasses

Over the past decade, oxy-fluoride glasses are the subject of investigation by many researchers. Calcium fluoride incorporated alumina-bismuth borate glasses reinforced with minute quantity of copper ions have been synthesized by melt-quenching process and the amorphous nature is approved by X-ray diffraction (XRD) spectra. The samples are further analyzed, to know the effect of Al₂O₃ on CaF₂-Bi₂O₃-B₂O₃–CuO glasses, with the help of density, molar volume, optical, electron paramagnetic resonance (EPR), and Raman and Fourier transform infrared (FTIR) spectra. A decreasing trend was observed in density values with increasing Al₂O₃ even though the relative density of Al₂O₃ is higher than the CaF₂. This decrease in density is attributed to the larger bond length of Al-O in AlO₄ units as compared to B-O bond length in BO₃ and BO₄ units. The bandgap values estimated from optical absorption spectra were found to increase with Al₂O₃ content, indicating the decrement in the number of non-bridging oxygens. Spin-Hamiltonian parameters \({g}_{\parallel }\)>\({g}_{\perp }\)>\({g}_{\mathrm{e}}\) (\({g}_{\mathrm{e}}\) = 2.0023) and \({A}_{\parallel }\) \(>{A}_{\perp }\) are of the opinion that the Cu²⁺ ions were taken the positions of octahedral sites with tetragonal distortion and ground state being \({d}_{{\mathrm{x}}^{2}-{\mathrm{y}}^{2}}\) orbital. FTIR and Raman spectra suggested that these glasses are composed of BiO₆, BO₃, BO₄, and alumina polyhedral.