Use of Pressure to Investigate Local Symmetry and Compressibility in Glass

Abstract

The effect of pressure to 120 kbar has been studied in several silicate and phosphate glasses. Transition metal ions have been introduced as tracers, and from the effect of pressure on the peak locations and intensities, local symmetry, local compressibility, and local distortions are deduced. Tetrahedral sites are less compressible than octahedral sites. Both are less compressible than the bulk glass and about as compressible as transition metal oxides. Fe2+ and Ni2+ apparently enter octahedral sites which show nearly the bulk compressibility, and considerable distortion. With increasing pressure there is a tendency for Co2+ and Ni2+ ions to transfer from tetrahedral to octahedra sites, as is predicted from the direction of change of site preference energy with pressure. There is an irreversible change in structure of the phosphate glass above 50 kbar.