Enhancing the densification of nanocrystalline TiO₂ by reduction in spark plasma sintering

Fully densified TiO₂ was obtained from spark plasma sintering (SPS) nanocrystalline rutile powder at a temperature of 720°C. The TiO ₂ was densified under an applied pressure of 40 MPa at 720°C. However, the applied pressure was not great enough to cause plastic deformation within the TiO₂ nanoparticle compact. Therefore, simple plastic deformation by applied pressure could not lead to the abrupt densification of TiO₂ during the SPS. In this work, the abrupt densification of nanocrystalline TiO₂ was examined at a low temperature in terms of the Joule heat caused by the flow of current through the compact due to the reduction of Ti⁴⁺ to Ti³⁺.