Plasma in spark plasma sintering of ceramic particle compacts

Cuboidal LiF microcrystal powder was densified by spark plasma sintering at different pressures up to 500 °C. Densification at pressures above the yield stress occurred by plastic deformation and strain hardening. Densification at 2 MPa, below the yield stress, occurred by particle rearrangement assisted by viscous flow at the particle surfaces. Scanning electron microscopy examination of the fracture surfaces of the partially dense specimens revealed partial melting of the particle surfaces due to the plasma. The onset temperature for plasma formation was ∼180 °C.