High pressure densification of lithium silicate glasses

We have carried out neutron diffraction and Raman scattering measurements o n the lithium disilicate glass densified by the application of high pressur e. The density of the glass increased monotonically with applied pressures up to 6 GPa. A shift of the first sharp diffraction peak (FSDP) toward larg er Q vectors was found in the total structure factor sce) of the neutron di ffraction spectra. The Si-O bond length in an SiO4 tetrahedron elongated by about 0.001 nm after densification under 6 GPa, while the nearest O-O dist ance did not change. However, an increase in distribution of the 0-0 distan ce was found after the densification. A low energy shift of 1080 cm(-1) ban d, which is assigned to Si-O stretching mode, was observed in Raman scatter ing spectra of the densified glasses. It is consistent with the increase of Si-O bond length. We deduced from these results that the densification is caused by an increase of packing density of SiO4 tetrahedron, which is acco mpanied by a distortion of the tetrahedron. (C) 2000 Elsevier Science B.V. All rights reserved.