Grain refining in spark plasma sintering Al₂O₃ ceramics

The paper reports the effect of starting powder size and sintering temperature on the grain refining in spark plasma sintering Al₂O₃. It was found that the grain refining effect only occurred for the starting particles larger than a certain size. The grain size increased with increasing sintering temperature. The grain refining is likely caused by the rearrangement of dislocations through a thermo-mechanical fatigue process. It suggested that nanostructured alumina ceramics could be synthesized from micro-sized powders by optimizing the particle size and sintering temperature.