Effects of the Residual Water on the Transformation Temperature and the Structure of BaO-P2O5 Glasses

Water content of BaO-P2O5 glasses prepared by various preparation conditions was determined by chemical analysis and the effects of the residual water on the transformation temperature and the structure of these glasses were investigated. Following conclusions were obtained.(1) The transformation temperature of the glasses is exceedingly influenced by preparation condition.(2) The cause of such a variation of transformation temperature is attributed to the change of water content in the glasses.(3) Water content in the glasses is 1-3 wt% and varies according to preparation condition and composition.(4) The cause why such a considerable amount of water is contained in the glasses is attributed to the nature of the chemical bond of PO4 group; that is, the branching point P*O4 group is unstable according to Van Wazer's “Antibranching Rule of PO4 group”. Therefore, it is assumed that the residual water in the glasses exists as OH group as in the following.-O-O|P|O|-*O-O|P|O|-*O-+H2O→←-H2O2[-O-O|P|OH-O-](5) Considering “Antibranching Rule” and high volatility of P2O5 component, the preparation of water free BaO-P2O5 glasses is impossible.(6) Since the water in the glasses can be regarded as the network modifier in the glass structure, residual water has a great influence on the transformation temperature of the glasses.