Influence of CaO on the structure of zinc sodium tetra borate glasses containing Cu2+ ions

A set of sodium tetra borate glasses doped with Cu2+ ions, with formula xCaO-(40-x)ZnO-59Na2B4O7-1CuO where x=0, 10, 20, 30 & 40 mol% were successfully prepared. The decrease in the density values of the glasses with the composition revealed the conversion of BO4 to BO3 units. Several physical and optical parameters were evaluated using density and optical absorption spectra. Of the expected four parallel and perpendicular resonance signals, three signals were clearly resolved in the EPR spectra, the fourth parallel component merged with the perpendicular ones. The spin-Hamiltonian parameter values confirmed the Cu2+ ions are in tetragonally distorted in octahedral sites. Deconvoluted spectra were drawn to extract the hidden peak positions in the FTIR and Raman spectra and residue graphs were used to find their accuracy. The fraction of BO4 groups (N4) values was calculated from the FTIR spectra and the N4 values supported the conversion of BO4 to BO3 units.