Optical absorption and EPR studies on (70 − x)Bi 2O 3– xLi 2O–30(ZnO–B 2O 3) (0 ⩽ x ⩽ 20) glasses

Abstract

Glasses with composition (70 − x)Bi 2O 3– xLi 2O–30(ZnO–B 2O 3) where (0 ⩽ x ⩽ 20) have been prepared using melt quench technique. DSC studies showed that the glass transition temperature increases with Bi 2O 3 content. Optical absorption spectra of the pure glasses reveled that the cut off wave length increased and optical band gap energy decreased with increase in Bi 2O 3 content. Electron paramagnetic resonance (EPR) and optical absorption studies of zinc-bismuth based glasses were made by introducing Cu 2+ as a spin probe. It is observed that the spin-Hamiltonian parameters calculated from the EPR spectra are influenced by the glass composition. The Cu 2+ ions are in well-defined axial sites but subjected to small distortion leading to the broadening of the spectra. The spin-Hamiltonian parameter values indicate that the ground state of Cu 2+ is d x 2 - y 2 and the site symmetry around Cu 2+ ions is tetragonally distorted octahedral. The optical absorption spectra exhibited a broad band corresponding to the d– d transition bands of Cu 2+ ion. By correlating EPR and optical absorption data, the bond parameters are evaluated and correlated with the optical basicity of the glasses obtained from various techniques.