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 Buori de glasses, mixed ionic and covalent SiO2-based oxide glasses, and a covale nt GeS2 sulfide glass at temperatures of about three-quarters of their resp ective glass-transition temperatures under pressures up to 9 GPa. The densi ties of GeS2 glass and silicate glasses of SiO2 contents > 50 mol% increase d with increasing applied pressure. In ZrF4-based glasses and silicate glas ses with SiO2 contents < 50 mol%. on the other hand, the densities increase d until an applied pressure around 3 GPa. the maximum densities were measur ed 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 kno wledge. (C) 2001 Elsevier Science B.V. All rights reserved.