Redox reactions in condensed oxide systems: III. Glass formation and properties in the Bi 2O 3P 2O 5 system

Abstract

Glass formation in the system (Bi 2O 3) x (P 2O 5) 1− x is reported by application of a pre-reaction technique on Bi 2O 3/H 3PO 4 mixtures of a mole ratio of 1:6 followed by evaporation and calcination yielding amorphous Bi 3P 7O 22 as a starting material which can be reproducibly transformed into a light glass Bi 2P 4O 13 at 1000°C or into a dark brown glass Bi 4(P 2O 7) 3 at 1200°C by melting without any action on Pt. Holding the former for some time at 1200°C before casting results in a black brown glass, and the latter yields a nearly colourless glass at 1000°C in both cases without changing the composition. It is found that the reversible variation of the absorption spectrum is caused by a very small liberation of oxygen from the melt at the higher temperature or by entrance of air at the lower temperature, respectively. The properties of the glasses are compared. Some tenths up to some per cents of Bi in a lower oxidation state are formed depending on the temperature. Light scattering measurements indicate the formation of clusters in the dark kinds of glasses.