Dynamic compression of TiO2 to 221 GPa

The high-pressure dynamic response of titanium dioxide (TiO2) is not only of interest because of its numerous industrial applications but also because of its structural similarities to silica (SiO2). We performed plate impact experiments in a two-stage light gas gun, at peak stresses from 64 to 221GPa to determine the TiO2 response along the Hugoniot. The lower stress experiment at 64 GPa shows an elastic behavior followed by an elastic-plastic transition, whereas the high stress experiments above 64 GPa show a single wave structure. Previous shock studies have shown the presence of high-pressure phases (HPP) I (26 GPa) and HPP II (100 GPa); however, our data suggest that the HPP I phase is stable up to 150 GPa. Using a combination of data from our current study and our previous Z-data, we determine that TiO2 likely melts on the Hugoniot at 157 GPa. Furthermore, our data confirm that TiO2 is not highly incompressible as shown by a previous study.