DENSIFICATION OF MAGNESIUM AND CALCIUM METAPHOSPHATE GLASSES

Magnesium and calcium metaphosphate glasses have been treated at high pressure and the effect of densification on mechanical properties has been examined. The density, Young's modulus and Vickers' hardness increase with pressure treatment. This effect is largest for magnesium metaphosphate glass. This observation indicates that the magnesium metaphosphate glass contains a larger amount of voids in the glass network structure than the calcium metaphosphate glass. This may be a consequence of the smaller coordination number of Mg2+ ion than that of Ca2+ ion. Fracture toughness decreases with pressure treatment indicating that a decrease in number and size of the void leads to the decrease in probability of irreversible processes such as the plastic deformation, crack branching and vibrational energy dissipation in the crack propagation at the crack tip. Inhomogeneous fluorescence spectra of Eu3+-doped metaphosphate glasses also show the structural change.