Alkaline earth zinc borate glasses doped with Cu2+ ions studied by EPR, optical and IR techniques

Copper ions incorporated into alkaline earth zinc borate glasses 10RO + 30ZnO + 60B2O3 (R = Mg, Ca and Sr) and 10SrO + (30 − x)ZnO + 60B2O3 + xCuO (x = 0, 0.1, 0.3, 0.5, and 0.7 wt.%) were characterized by electron paramagnetic resonance (EPR), optical absorption and FTIR techniques. The EPR spectra of all the glass samples exhibit resonance signals characteristic of Cu2+ ions. The values of spin-Hamiltonian parameters indicate that the Cu2+ ions in alkaline earth zinc borate glasses were present in octahedral sites with tetragonal distortion. The spin concentration (N) participating in resonance was calculated as a function of temperature for strontium zinc borate (SrZB) glass sample containing 0.7 wt.% of Cu2+ ions and the activation energy was calculated. From the EPR data, the paramagnetic susceptibility (χ) was calculated at different temperatures and the Curie constant was evaluated from the 1/χ-T graph. The optical absorption spectra of these samples show only one absorption band. The optical band gap energies (Eg) and Urbach energy (ΔE) are calculated from their ultraviolet edges. The FTIR studies show different stretching and bending vibrations of alkaline earth zinc borate glasses.

Research Highlights
► From the EPR data, spin-Hamiltonian parameters, spin concentration (N) and magnetic susceptibility (χ) have been evaluated.
► The optical absorption spectra of these glass samples show single broad band due to Cu2+ ions in distorted octahedral sites.
► By correlating the EPR and optical data, the molecular orbital coefficients α2 and β21 are calculated.
► The molecular structure for the strontium zinc borate glasses was explaind by FTIR analysis.