Flash Sintering of dense alumina ceramic discs with high hardness

Abstract MgO-doped-Al2O3 ceramic discs were fabricated by flash sintering (FS) and pressureless sintering (PS). The results showed that MgO-doped Al2O3 exhibited typical characteristics of flash sintering under an electric field in excess 2500 V/cm. Compared with the PS- fabricated specimen, the flash sintered specimens exhibited sub-micron grains (≤760 nm) and homogeneous microstructures. The relative density of the flash sintered MgO-doped Al2O3 ceramics increased with current density, reaching 99.91 % when the current density increased to 7 mA/mm2. The FS-fabricated sample exhibited higher hardness (21.02 GPa) and fracture toughness (3.46 MPa m1/2) than PS-fabricated sample.