Theoretical studies of the concentration dependences of g factor and d-d transition band for Cr3+ in CdO-SrO-B2O3-SiO2 glasses

The concentration dependences of g factor and d-d transition band are theoretically studied for Cr3+ in CdO-SrO-B2O3-SiO2 glasses in a consistent way. To determine the local structure around dopant Cr3+, the non-bridge oxygen (NBO) occupation ratio o is calculated for different dopant concentrations x. In order to evaluate explicitly the influences of other cations (e.g., Sr2+) and to refine the conventional bulk optical basicity of whole glass systems, a new quantity local optical basicity Lambda(loc) around dopant Cr3+ is introduced to describe the influences of local environments on the studied [CrO6] clusters. This new quantity is also theoretically characterized by o related to NBO concentration f (NBO). The concentration dependences of cubic field parameter Dq and isotropic g factor are suitably reproduced by three piecewise linear functions of Dq and orbital reduction factor k with x. The microscopic mechanisms of the relationships of crystal-field strength and covalency of [CrO6] clusters with x are analyzed in view of the variations of Lambda(loc) and high ionicity of Sr2+ nearby at different stages. (C) 2016 Elsevier B.V. All rights reserved.