Key microstructural characteristics in flash sintered 3YSZ critical for enhanced sintering process

To explore the fundamental flash sintering mechanisms in yttria-stabilized zirconia (3YSZ), a detailed micro structural characterization based on transmission electron microscopy (TEM) has been conducted on 3YSZ flash sintered in air and Ar atmospheres. The study combines the surface morphology characterization via scanning electron microscopy (SEM) and the detailed grain structure analysis based on TEM. The results show that large clusters are comprised of very fine nanocrystalline subgrains, possibly caused by global grain boundary sliding and grain rotation which occur during the flash sintering process. Dislocation arrays were found near grain boundary triple junctions, suggesting the high mass transport rate during the rapid densification process in flash sintering. Yttrium-segregation was observed at grain boundaries near triple junctions as the result of the electrochemical forces.