LAUSR

Melt-quenching technique was used to prepare borosilicate glasses of composition xSiO2- (75-x) B2O3–24.7Li2O-0.3Cr2O3 (x = 0, 10, 20, 30, 40 and 50 mol%). With increasing the former content, both Cr6+ and Cr3+ optical transitions undergo strong intensity variations. The crystal field strength (10Dq) is increased, while Racah parameters (C,B) are decreased with increasing SiO2 content. The ratio estimated Dq/B values confirmed a weak crystal field environment for Cr3+ions, and further suggest a more covalent bond character. The ESR results revealed that Si-contained samples exhibit a strong microwave absorption signal, and justified the presence of both Cr3+ and Cr6+(charge transfer into 3d0 2p6+ = 3d1Cr5+) oxidation states. The fingerprints of borate and silicate relevant structural groups were clearly identified from FTIR spectroscopy.