2026/07/25 by Qin-Kun Li, Evgeni S. Penev, Boris I. Yakobson
Physics and Astronomy · #cond-mat.mtrl-sci
arxiv created 2026/07/30 · arxiv updated 2026/07/31
The atomistic understanding of flash sintering (FS) remains speculative, despite its efficiency and versatility in materials processing. Employing first-principles calculations we demonstrate how charge compensation of a range of defects in the prototypical Y-stabilized cubic ZrO2 (YSZ) shifts Fermi level EF up during FS, thereby accelerating cation migration for fast mass transport. The charge transition of Zr vacancy, VZrq, reduces its bulk diffusion barrier in VZr-4 during flash by 2 eV, relative to VZr0 before flash, which is triggered by the charge equilibrium of nonstoichiometric defects. The substituent defect YZr, released by annihilating O vacancy, VO, in YZrVOYZr defect complex, acts as electron acceptor and favors VZr0 before flash whereas excess VO, as electron donor thermally generated at the FS onset, upshift EF and thus support VZr-4. The proposed mechanism of Fermi-level mediated cation diffusion for YSZ is generalized to other flash-sintered ceramics and has considerable bearing on the general theory of FS techniques in oxide ceramics.