  Dopants can significantly affect the properties of oxide ceramics through
their impact on the property-determined microstructure characteristics such as
grain boundary segregation, space charge layer formation in the grain boundary
vicinity, and the resultant microstructure features like bimodality due to
abnormal grain growth. To support rational oxide ceramics design, we propose a
multiphysics-based and defect-chemistry-informed phase-field grain growth model
to simulate the microstructure evolution of oxide ceramics. It fully respects
the thermodynamics of charged point defects (oxygen vacancies and dopants) in
both the grain interior and boundaries and considers the competing kinetics of
defect diffusion and grain boundary movement. The proposed phase-field model is
benchmarked against well-known simplified bicrystal models, including the
Mott-Schottky and Gouy-Chapman models. Various simulation results are presented
to reveal the impacts of defect formation energy differences between the grain
interior and the grain boundary core on the key microstructural aspects. In
particular, simulation results confirm that the solute drag effect alone can
lead to bimodal grain size distribution, without any contribution from grain
misorientation and other anisotropy. Interestingly, abnormal grain growth
simulations demonstrate that grain boundary potentials can vary substantially:
grain boundaries of larger grains tend to have lower potentials than those of
smaller grains. Such heterogeneous grain boundary potential distribution may
inspire a new material optimization strategy through microstructure design.
This study provides a comprehensive framework for defect-chemistry-consistent
investigations of microstructure evolution in polycrystalline oxide ceramics,
offering fundamental insights into in-situ processes during critical
manufacturing stages.
