Welding of yttrium-doped zirconia granules by electric current activated sintering (ECAS): Protrusion formation as a possible intermediate step in the consolidation mechanism

The basic mechanisms of the current activated/assisted sintering (ECAS) of yttrium-doped zirconia's currently is a controversial issue. To gather more experimental data, we performed two-electrode-experiments (2EE) on staked spherical granules of cubic yttria-stabilised zirconia (YSZ) of diameters ranging from 10 to 100 μm. The observations were focused on the initial welding stage, under currents smaller than 4 A cm−2. The impedance spectroscopy appears to be a sensitive technique to detect the very early welding stage. FEG-SEM analysis reveals protrusion formations at the granule surfaces which are probable intermediate microstructures in the neck formation.