Density, viscosity and surface tension of 50RO-50P2O5 (R: Mg, Ca, Sr, Ba, and Zn) glass melts

The density, surface tension and viscosity of the 50RO-50P₂O₅ (R: Mg, Ca, Sr, Ba and Zn) glass melts have been measured over the range, 1073-1623 K. The effects of R cations on these properties have been investigated. The density of the melt was found to increase in the order, R: Mg<Ca<Zn<Sr<Ba, with increasing molar weight of cation. The surface tension in the temperature range of 1373-1473 K increased approximately with cation in the order, R: Zn<Ba<Mg<Ca<Sr. The viscosity and the negative, temperature coefficient of surface tension increased in the order, R: Ba<Sr<Ca<Zn<Mg. All melts exhibited negative temperature coefficients of surface tension. The effect of Mg and Zn cations on the properties were different to that for Ba, Sr, and Ca cations and this is discussed using bulk glass data published in a previous report. The features of Mg and Zn metaphosphate glass melts, that is high values of viscosity, and temperature coefficient of surface tension, are related to the small Oxygen Coordination Number of the cations (=4) when compared with those of Ca, Sr, Ba metaphosphate glass melts.