The effect of Li2O and LiF on structural properties of cobalt doped borate glasses

Two glassy (LiF-B2O3) and (Li2O-B2O3) systems containing different content of CoO dopants (0.05, 0.1, 0.15, 0.2 wt%) were prepared. UV/Vis optical absorption of base glasses reveals a strong UV absorption bands attributed to unavoidable contaminated trace iron impurities. CoO-doped glasses show extra three visible bands due to both octahedral and tetrahedral Co2+ ions related to the little variation between energies of ligand field stabilization between the two coordination states. Fluoride containing glasses show limited variations in the spectral properties due to the different ligand strength of the anions (F− and O2−). FTIR spectra display characteristic modes of vibrations due to triangular and tetrahedral borate groups. It is assumed that LiF acts as Li2O in promoting the formation of tetrahedral (BO3F) units which possess the same wavenumber position for vibrations of (BO4) units in the range of 800-1200 cm−1. CoO causes no distinct variations in number or position of characteristic IR vibrational bands due to their low dopant level (0.05-0.2%). A new suggested trial has been utilized to calculate the percent of four coordinated borons from both optical and FTIR spectra to give more insight on the role of CoO as dopant on these spectral properties and on the calculated parameters.