Physical, optical and structural studies of copper-doped lead oxychloro borate glasses

Bluish coloured glasses are obtained from the composition PbCl $$₂$$ –PbO–B $$₂$$ O $$₃$$ doped with Cu $$²⁺$$ ions. Basic physical properties and spectroscopic studies (optical absorption, electron paramagnetic resonance, Fourier transform infrared and Raman spectroscopies) were carried out on these samples. The increase in PbCl $$₂$$ content resulted in the decrease in density and increase in molar volume. At optical frequencies, band gaps and Urbach energies were evaluated and their variation is explained. Spin-Hamiltonian parameters (SHP) obtained from the EPR spectra suggest that the ligand environment around Cu $$²⁺$$ is tetragonally distorted octahedral sites and the orbital $$d_{x²-{y}²} $$ is the ground state. The characteristics broad bands in the optical absorption spectra are assigned to the $$²$$ B $$_{\mathrm{1g}}\,\rightarrow \, {}²$$ B $$_{\mathrm{2g}}$$ transition. The bonding coefficient values were evaluated using optical data and SHP. FTIR studies suggested that the glass structure is built up of BO $$₃$$ and BO $$₄$$ units. The presence of diborate, pyroborate, pentaborate groups, etc. in the glass network was confirmed from Raman spectra.