EPR, optical, physical and structural studies of strontium alumino-borate glasses containing Cu2+ ions

Glass composition (30 − x) SrO–xAl2O3–69.5B2O3–0.5CuO (0 ≤ x ≤ 15 mol%) captioned as SABC was prepared by the conventional melt quenching technique. Peak-free X-ray diffractograms and homogeneous plain SEM image confirm the glassy nature of the prepared samples. EPR and optical absorption spectral studies were carried out to understand the effect of modifier oxide (SrO) and transition metal (TM) ion Cu2+ in the glass network. From the EPR spectra, spin-Hamiltonian parameters were evaluated. It was observed that g‖>g⊥>geandA‖>A⊥\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$g_{\parallel } > g_{ \bot } > g_{e} \,{\text{and}}\,A_{\parallel } > A_{ \bot }$$\end{document} suggest that the ground state of Cu2+ is  dx2-y2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$d_{{x^{2} - y^{2} }}$$\end{document} (2B1g state) and the site symmetry around Cu2+ is tetragonally distorted octahedral. The optical absorption spectra revealed a broad absorption for all the glass samples. This band is assigned to 2B1g → 2B2g transition. From optical absorption spectra, optical band gap and Urbach energy values were calculated. The FTIR and Raman spectral studies showed that the glass network consists of BO3 and BO4 structural units.