In situ fabrication of continuously graded Si3N4 ceramics via DC field-assisted hot pressing

The effects of various DC electric fields (0–167 V/cm) on liquid-phase hot pressing of Si 3 N 4 ceramics were investigated. The application of a DC field promoted the α→β phase transformation of Si 3 N 4 near the cathode while inhibiting it near the anode. As a result, the Si 3 N 4 ceramics with continuously graded microstructures and mechanical properties were in situ fabricated from a homogeneous raw powder. Although the DC field-driven migration of Mg 2+ and Y 3+ ions was recorded, the graded phase transformation phenomenon was linked to the Peltier effect , which led to additional heating at the cathode and cooling at the anode.