# Atomic‐Scale Insights into Yttrium‐Induced Grain Boundary Structure Modification in Al2O3

## TL;DR

This study explores how yttrium affects grain boundary structures in aluminum oxide at the atomic level, revealing new insights into material property changes.

## Contribution

The novel contribution is the discovery that yttrium segregation involves structural adaptation, not just substitution, minimizing excess volume at grain boundaries.

## Key findings

- Y segregation at grain boundaries involves structural adaptation and changes in atomic density.
- The adaptation minimizes absolute excess volume for the lowest-energy grain boundary structure.

## Abstract

Impurity segregation at grain boundaries (GBs) often induces structural transformations at the atomic level and significantly influences materials’ properties, underscoring the importance of understanding the underlying mechanisms of GB segregation at the atomic scale. Here, the atomic structure of a Y‐segregated ∑13(101¯4)/[1¯21¯0] GB is thoroughly studied in α‐Al2O3 via scanning transmission electron microscopy and Monte Carlo and molecular dynamics simulations based on a neural network potential. It is found that the Y segregation at the GB involves not only the simple substitution of Y for Al atoms but also a structural adaptation with a change in GB atomic density. Such a change alters the local bonding environment at the GB so that the absolute excess volume is minimized for the lowest‐energy structure. This study offers a new insight into the atomic‐scale mechanism of GB structural transformation.

Using advanced STEM characterization combined with NNP‐based MCMD calculations, it is revealed that Y segregation at ∑13 Al2O3 GB involves not only simple substitution of Y for Al atoms but also structural adaptation with a change in GB atomic density, leading to minimized excess volume and lowest GB energy. This work deepens the understanding of GB segregation at the atomic scale.