Microstructural temperature gradient-driven diffusion: Possible densification mechanism for flash sintering of zirconia?

Flash sintering represents an innovative electric field-assisted sintering technology which allows a drastic reduction of the consolidation time and temperature of many ceramics. It is still under debate whether and how the electric field and current boost the densification process. In this work, we investigate the impact of microstructural temperature gradients, associated to an overheating of the interparticle contact points, on mass transport in the different stages of flash sintering of yttria-stabilized zirconia (YSZ). Although the temperature difference between grain bulk and boundary is limited, it is associated to extremely high gradients as a result of the small particle size. In such conditions, a temperature gradient-driven atom flux can be activated. The calculations point out that thermodiffusion can significantly accelerate densification of micrometric YSZ powder upon flash sintering if the thermal gradients exceed 106 K m−1.