The structure and properties of vanadium zinc phosphate glasses

Homogenous bulk glasses of the ternary system xV2O5-(50-x)ZnO-50P2O5, x = 0-50 were prepared using the conventional melting procedure. The influence of an increasing content of vanadium on their structure and certain physical properties was investigated. Raman spectra revealed a strong depolymerization of the original metaphosphate network for x > 10, the non-bridging oxygens are involved in the VOP bonds. With an increasing content of V2O5, the intensity of VOV vibration increases. ESR results indicate the partial reduction of V+ V to V+ IV, with the latter being present as VO2 + ions in axially distorted sites with C4v symmetry. The optical absorption spectroscopy is shown to be more sensitive to changes in the vicinity of isolated paramagnetic vanadium centres than ESR and indicated a decrease in symmetry from C4v to C2v. The basic physical characteristics (density, molar volume, glass transition and softening temperatures and thermal expansion coefficient) were measured and discussed in connection with structural changes.