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 ZrF 4 -based fluoride glasses, mixed ionic and covalent SiO 2 -based oxide glasses, and a covalent GeS 2 sulfide glass at temperatures of about three-quarters of their respective glass-transition temperatures under pressures up to 9 GPa. The densities of GeS 2 glass and silicate glasses of SiO 2 contents >50 mol% increased with increasing applied pressure. In ZrF 4 -based glasses and silicate glasses with SiO 2 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.