A structural analysis of the physical properties of bismuth and lead basedglasses

We report on a series of measurements of the density and glass transition t emperature of a variety of glass families containing bismuth(III) and lead( II) oxide. Comparisons are drawn between the binary bismuth borate and lead borate systems and the behaviour of density and calculated molar volumes a re related to changes in the formation of four coordinated borons, lend tet rahedra and bismuth octahedra. The addition of an alkali oxide is considere d in a substitutional study of the xLi2O.cB(2)O(3).(1-c-x)Bi2O3 ternary sys tem and the compositional behaviour of the density of this system is modell ed using a simple mixing scheme of separate bismuth and lithium borate subn etworks. A similar investigation was performed an the binary bismuth and le ad silicate families indicating larger changes in the molar volume with the addition of the metal cation. Measurements of the density and transition t emperatures of the bismuth borosilicate family were also carried out. Ebr t he bismuth borosilicates the overall molar volume is increased as the amoun t of bismuth in the glass is increased but in the family Z=1 (where Z is th e molar ratio of silica to born) there is a compaction at low bismuth conce ntrations. A mixing model which utilises independent results from the binar y bismuth borate and silicate glasses was successful at reproducing the den sity trend and it pointed to a proportional 'strong mixing' of the separate silicate and borate subnetworks.