The position of silica glass in a series of compressibilities of silicate glasses in the pressure range up to 5.0 GPa

摘要

Relative changes in the density, (d-d(0))/d, of SiO2 glass in pressures up to 5.0 GPa were compared with the (d-d(0))/d values of aluminosilicate and magnesium silicate glasses in the M2O(CaO)-Al2O3(MgO)-SiO2 system (M=Li, Na, K). It is shown that the silica glass is not the most highly compressible among the silicate glasses, as can be expected in the case of an ideal structure of SiO2 glass (the ideal structure of fused quartz is characterized by the absence of nonbridging oxygen atoms in the fully polymerized structural network, NBO/T congruent to 0). The compressibility of silica glass is below that of aluminosilicate glasses with a high content of SiO2, such as KAlSi3O8 and NaAlSi3O8 glasses. This is related to the defect structure of SiO2 glass and the possible maintainance of abnormally high density of liquid silica in glass on cooling of the melt, due to its high viscosity.