Spectroscopic and mechanical studies of lithium aluminoborate glasses doped with chromium ions

Aluminoborate glasses, doped with chromium ions, were prepared using melt quenching technique. Spectroscopic and mechanical tools were utilized to study the impact of B2O3 substitution with Al2O3 on the structure of the glass system. Infrared spectra uncovered that substitution of B2O3 with Al2O3 causes concealment of non-bridging oxygen NBOs and creation of inflexible AlO4 tetrahedral. The UV-Vis absorption spectra demonstrated a blue-shift of the optical absorption edge with increasing Al2O3 content. The optical band gap was found to increase, while the refractive index diminished with addition of Al2O3 content. The calculated crystalline field Dq, Racah parameters (B and C) and Dq/B indicated the diminishment in inter-electron repulsion with increasing the covalency. In particular, a value of Dq/B larger than 2.3 assures that chromium ions are in strong ligand field sites. The elastic moduli increase with increasing Al2O3 content, due to the reduction NBOs and, consequently, the increased average bond connectivity.