High-pressure densification of fluoride, GeS2 and silicate glasses

Densification of glasses having different chemical-bond properties and also different structures have been examined by treating ionic ZrF4-based fluoride glasses, mixed ionic and covalent SiO2-based oxide glasses, and a covalent GeS2 sulfide glass at temperatures of about three-quarters of their respective glass-transition temperatures under pressures up to 9 GPa. The densities of GeS2 glass and silicate glasses of SiO2 contents >50 mol% increased with increasing applied pressure. In ZrF4-based glasses and silicate glasses with SiO2 contents <50 mol%, on the other hand, the densities increased until an applied pressure around 3 GPa, the maximum densities were measured at pressures around 3 GPa, and then decreased with increasing pressure. The pressure dependences of permanent densification observed in the latter glasses are a permanent densification that has not been reported to our knowledge.