A high temperature neutron diffraction study of a titanosilicate glass

Neutron diffraction experiments were performed on a K2O·TiO2·2SiO2 glass, from room temperature, through the glass transition region (Tg=885 K) and up to the liquid state (1360 K), in order to investigate the structural modifications that occur between the glass and the melt. Si remains in tetrahedral coordination in the liquid with a small expansion of the Si–O bond (0.01 Å at 1360 K). The Ti–O correlation has been extracted from the data to isolate the short Ti–O distance at 1.68 Å from the Si–O peak. Titanium does not undergo a significant coordination change and a short Ti–O distance can be detected in the glassy and liquid states. The diffraction data indicate an expansion of the long Ti–O distances (∼0.03 Å at 1360 K) and of the K–O distances (∼0.1 Å at 1360 K). Structural changes at the medium range distance are visible and may be responsible for the anomalous thermodynamic properties of these melts.