Oxide ceramics such as strontium titanate and barium titanate play key roles in capacitors, actuators, sensors, memristors, and fuel-cell technologies. Their performance is strongly influenced by microscopic structural features formed during processing, particularly grain boundaries—the interfaces between neighboring crystal grains.
In Fe-doped SrTiO₃, doping introduces charged point defects, including oxygen vacancies and acceptor dopants. These defects can segregate at grain boundaries and form space-charge layers, which are difficult to observe directly during high-temperature sintering but can strongly affect grain-growth behavior and charge transport in the final ceramic.
To better understand these hidden processes, the authors developed a phase-field grain-growth model explicitly informed by defect chemistry. The model distinguishes the segregation energies and available site densities of oxygen vacancies and acceptor dopants in grain interiors and grain-boundary cores, while also accounting for the competition between defect diffusion and grain-boundary migration.
The model was benchmarked against established bicrystal descriptions, including the Mott–Schottky and Gouy–Chapman models. Simulations then revealed how defect-chemistry parameters govern the formation of space-charge layers, grain-boundary potentials, and grain-size evolution during sintering.
One important finding is that solute drag alone can drive grain growth away from the conventional log-normal behavior. The simulations produced skewed grain-size distributions even without considering grain misorientation or anisotropic grain-boundary mobility. This result provides new insight into the origin of abnormal grain growth in doped oxide ceramics and highlights the critical role of defect segregation.
The simulations also suggest that grain-boundary potentials can vary substantially throughout a polycrystalline microstructure. At later stages of grain growth, smaller grains tend to exhibit higher grain-boundary potentials and stronger blocking effects on ionic transport, whereas larger grains tend to show lower potentials. This heterogeneity may offer opportunities for microstructure design: conductivity could be enhanced by promoting current pathways that bypass blocking boundaries, while applications such as capacitors may benefit from maintaining smaller grains and preserving blocking grain boundaries.
The work, titled “A defect-chemistry-informed phase-field model of grain growth in oxide ceramics: application to Fe-doped SrTiO₃”, was published in Advanced Powder Materials (Available online on 29 April 2026).
DOI:10.1016/j.apmate.2026.100425