Structure-property correlation in (50 − x)Na2O–50P2O5–xCoCl2 glassy systems

Ternary sodium–cobalt–phosphate glasses of the composition (50 − x)Na2O–50P2O5–xCoCl2 with x varying between 0 and 15 mol% prepared by melt quenching have been characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) techniques. Thermal (Tg, Tc) and electrical properties have been investigated. Infrared spectra reveal the formation of metaphosphate glasses (Q2 tetrahedral units) with symmetric bridging oxygen (P–O–P) and non-bridging oxygen (P–O−). The spectra also indicate the formation of P–O–Co bonds in the metaphosphate glasses that replace P–O−–Na+ bonds. The results of thermal studies correlate with these FT-IR findings and support the formation of P–O–Co bonds and an increased cross-link density with increasing CoCl2. This results in enhanced chemical durability and increased Tg and Tc of the glasses. The electrical conductivity parameters upon changing the composition have been correlated with structural changes in the glass matrix.