Evaluation of EPR parameters for compressed and elongated local structures of VO2+ and Cu2+ spin probes in BaO-TeO2-B2O3 glasses

Abstract

Abstract EPR parameters and the local configurations of the transition metal (TM) ions VO2+ and Cu2+ in BaO-TeO2-B2O3 glasses were experimentally evaluated and also theoretically verified. From the recorded X-band EPR spectra the spin-Hamiltonian parameters (SHP) were determined. The optical spectra of vanadium doped glass samples revealed a single absorption band at 596\u202fnm which was assigned to 2B2g → 2B1g transition, whereas copper doped glasses revealed two absorption bands around 818 and 602\u202fnm which were assigned to 2B1g → 2B2g and 2B1g → 2E2g transitions respectively. Theoretical studies were accomplished on the EPR and optical factors from perturbation theory. It was observed from both the experimental and theoretical SHP values of vanadium containing glasses that the VO2+ ions are in tetragonally compressed octahedral sites with dxy (2B2g) ground state, while the copper containing glasses found to be in tetragonally elongated octahedral sites with d x 2 − y 2 (2B1g) as the ground state. It is found that the magnitude of the relative tetragonal compression ratio ( φ ) of vanadium ion is less than the relative tetragonal elongation ratio ( τ ) of copper ion. The nature of the bonding between TM ions (i.e. vanadium and copper) and their ligands was assessed. Theoretical and experimental EPR parameters are in great concurrence with each other.