Flash sintering incubation in Al2O3/TZP composites

The flash sintering incubation process was characterized with Al2O3/TZP composites in isothermal furnace experiments. The compositions in tetragonal zirconia, TZP and Al2O3 were 0, 20, 40 and 60 vol.% of Al2O3. AC electrical field E0 (1000 Hz) of 100 or 200 V/cm was used. The current density was limited at 10 or 20 A/cm2, and the pre-heating temperatures were 900, 1000 and 1100 °C. The flash phenomenon depends on the overall conductivity of the sample. For a constant electrical field, the incubation time only depends on the sample overall conductivity whatever its temperature or composition. The power density supplied to the sample is the key parameter. The incubation time is affected by the heat losses, which mainly occur by thermal conduction through the electrode contacts, as evidenced by the marked influence of the sample geometry. A simple energy balance equation accounts for the observed current variations.