Optical absorption and FTIR studies of Cu²⁺ ion doped in 25Li₂O-15BaO-(60-x) B₂O₃ glasses

Glasses with composition 25Li₂O-15BaO-(60-x) B₂O₃: x CuO (where x=0, 0.2, 0.4, 0.6, 0.8 and 1 mol %) were prepared using the conventional melt quench technique. The optical absorption spectra of studied glass samples show only one absorption band which is attributed to the 2B_1g→2B_2g characteristic transition of Cu²⁺ ions in the distorted octahedral sites. The cut-off wavelength (λ_c), optical band gap (E_opt) and Urbach energy (ΔE) were determined. The FTIR studies show different stretching and bending vibrations of alkaline earth lithium borate glasses. The relative variations in the intensities of BO₃ and BO₄ units in IR spectra with the concentration of CuO indicate that the copper ions mostly occupy modifying positions in the glass network when the concentration of CuO ≤ 0.8mol%.