Role of manganese in 20K2O-xMnO-(80-x)P2O5 phosphate glasses and model of structural units

Glasses with composition 20k2o-xmno-(80-x)p2o5 with 0≤x≤30 mol% were prepared by conventional melt quenching technique at 1100°c mixtures of k2co3,mnco3 and nh4h2po4. their density,molar volume,glass transition temperature and infrared spectroscopy have been investigated. differential scanning calorimetry (dsc) measurements give the variation of glass transition temperature (tg) from 225°c for x=0 to 440°c for x=30 mol %. the density (ρ) measurements increase from 2.28 to 2.89 g.cm-3. the evolution of infrared spectra with the composition is studied and the oxide forming character is discussed. when manganese oxide is added to potassium phosphate glass,phosphate chains are depolymerized by the incorporation of distorted (4) units through p-o-mn bonds. it is assumed to be presented as [mno4/2]2- structural units a corner sharing geometry and the electrical neutrality in the system is achieved by the conversion of [poo3/2] into [po4/2]+ units.