TRANSITION FROM SHORT-RANGE TO LONG-RANGE ORDER IN LEAD-BISMUTHATE OXIDE GLASS MATRICES

Glass transition and nucleation temperatures as well as densities and molar volumes of x Bi 2 O 3·y PbO (0.5≤x/y≤4) are reported. The glass transition temperature and molar volume are further analysed in terms of structural data. The obtained results indicate the occurrence of structural changes from short range to long range order induced by the heat treatment applied at 550°C, as per DTA results. These changes depend on the x/y ratio between Bi 2 O 3 and PbO content. The compositional variation of the molar volume of untreated and heat-treated samples are evidences that both Bi 2 O 3 and PbO play the role of network formers.