Infra-red Spectra and Some Physical Properties of Divalent Metal Phosphate Glasses Containing Residual Water

Abstract

Notwithstanding water content of phosphate glass is, in general, exceedingly greater than that of silicate or borate glass, it is rather difficult to gather informations about influences of water on structure and properties of glass.First, in purpose to study on this problem more thoroughly, the writers prepared a vast number of glass samples having the different values of MO/P2O5 ratio, RM, or (MO+H2O)/P2O5 ratio, RMH. Water content of glass was regulated by means of repeated remelting. Various series of samples suitable to understand the influences of water content on structure and properties of glass were taken up from those many samples prepared. And then, it was attempted to clarify behavior of water in glass structure.From the results of infra-red spectrophotometry and measurements of characteristic properties of glass, it was proved that, in whichever system, RMH had much more important significance as a composition parameter rather than RM.In reference to RMH and RM values, considering behaviors of the end and the middle OH-groups in glass structure and the effects of electron donating power of element M and field strength or polarizability of M2+ ion on hydrogen bond (OH…O) in glass, one can explain, from a structural viewpoint, the influences of residual water on the characteristic properties of glass, especially, density and refractivity. Thus, the following interesting findings were obtained.(1) Density of glass decreased with decreasing water content. This reveals that, in general, dehydration makes to expand the glass structure. However, in case that the middle OH-groups in glass of anomalous type, e.g., those in the system MgO-or ZnO-P2O5, were obliged to be removed from the structure, the glass resulted in structural contraction rather than expansion.(2) In respect to the series of samples almost constant in H2O/P2O5 ratio, it could be found that an anomalous change of density and refractivity occurred when RMH=1. Therefore, RMH-value should be dealt with as a conclusive composition parameter for marking the structure exchange of water containing phosphate glass. Especially, the physical properties of magnesium phosphate glass showed a drastic change at the critical composition, presumably, on account of a particularity of the glasses of anomalous type.