On the role of the electric field in the last-stage sintering of ceramics: A phase-field modelling approach

“Field-assisted sintering techniques” (FAST) are one of the landmarks for ceramists nowadays. From the beginning of their discovery, their physical mechanisms are a pending question. In this paper, the growth of a collective of 3D ceramic grains (with or without an electric field) has been modelled through phase-field. The model allows switching off thermal effects from pure non-thermal electrodynamical ones. The results show that strong electric fields affect the sintering process, but, contrary to usual statements, they retard grain growth. This effect weakens as temperature rises. Therefore, the origin of FAST techniques must have a thermal component A hypothesis is proposed: local non-homogeneities of transport properties at the grains are demonstrated to induce intense temperature gradients even in stationary conditions, and it can act as driving force for flash. The intrinsic cause of electric field-induced inhomogeneities must be related to local atomistic processes, which are still unknown.