A comprehensive identification of optical transitions of cobalt ions in lithium borosilicate glasses

Abstract Exploring the materials with distinct optical properties is still in progress. Hence, Co-doped lithium borosilicate glasses of composition x Li 2 O–(80 – x ) B 2 O 3 –19.6 SiO 2 –0.4 CoO ( x  = 5, 10, 15 and 20 mol%) were synthesized via communal melt quenching method. XRD affirmed the amorphous essence of such glasses. Local structure of such glasses was explored via FTIR spectroscopy. Simultaneously, the BO 4 structural units in such glasses decreased with Li 2 O additions, rendering the open structure. Additionally, the density of such glasses decreased by Li 2 O addition, consequently, causing an open structure. The systematic substitution of B 2 O 3 by Li 2 O affected the optical basicity and electronic polarizability of such glasses, causing the increase of NBOs ratio and ionic nature of such glasses. Interestingly, the optical transitions of Co-ions embedded in lithium borosilicate glass system were investigated. The optical band gaps provided lower values together with evident augmentation of band tails with Li 2 O addition. The processes of deconvolution and focusing of optical spectra were implemented on the characteristic bands of cobalt to obtain more visions into the crystal field interaction and d-levels splitting. The consequence of such processes revealed obvious reductions in the ligand field strength upon Li 2 O addition, leading to reduce d-levels splitting. Moreover, the metallization criterion values were changed from 0.41 to 0.37, rendering a semiconducting character to such glasses. Given the Co 3+ /Co 2+ optical transitions in both visible and NIR spectral regions and their possible tunability through Li 2 O additives, such glasses are significantly useful for the development of optically active materials besides offering the prospect applications in various optical devices.