Effect of external electric field on diffusivity and flash sintering of 8YSZ: A molecular dynamics study

The atomistic structural modification and ionic diffusivity in 8YSZ at elevated temperature with the presence of an external electric field (E-field) were investigated by molecular dynamics (MD) simulations. As an example, a sufficiently large system of atomic configuration for a bi-crystal Sigma 5(310)/[001] grain boundary (GB) model was studied. MD results show that the E-field promotes the formation of Frenkel pair defects. Notably, some Zr ions diffuse out of GB regions at E-field greater than or similar to 500-1000V/cm, resulting in an "avalanche" of cation vacancies at GBs and reduction of GB space charge. Consequently, the diffusivities of cations and anions are enhanced in the 8YSZ system with the presence of E-field. The atomistic level understanding of E-field induced structural modifications and ionic diffusivities provide an in-depth insight to unravel the flash sintering mechanisms of ionic ceramics, especially the coupled thermal-field effect during the flash sintering process. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd.