Li2B4O7 glasses doped with Cr, Co, Eu and Dy

Absorption and emission spectra of Cr, Co, Eu and Dy ions in Li2B4O7 glasses melted in oxygen and hydrogen were measured for valency states analysis. It was stated that the presence of Cr6+ ion is limited by composition of the starting mixture and atmosphere of the melting and that this ion arises as Cr6+O- complex. Independently of the above factors in all the glasses there were present Cr3+ ions. Under gamma-irradiation Cr6+O- complex of 3d(0) configuration can be disintegrated giving additional absorption band of Cr3+ and may be Cr4+ and higher valency centers. Corresponding photoluminescence is centered at about 430 nm. Absorption of Li2B4O7:CO glasses obtained in oxygen atmosphere reveals Co2+ and Co3+ ions which does not give any emission in the UV-VIS and near-infrared region of luminescence spectrum. The content and optical characteristics of Eu2+ and Eu3+-doped Li2B4O7 glasses are dependent of the growth atmosphere. (C) 2002 Elsevier Science B,V. All rights reserved.