Direct Visualization of Distorted Twin Boundaries in Ce-Doped GdFeO3

Utilizing advanced transmission electron microscopy (TEM), the structure at the (110)-type twin boundary (TB) of Ce-doped GdFeO3 (C-GFO) has been investigated with picometer precision. Such a TB is promising to generate local ferroelectricity within a paraelectric system, while precise knowledge about its structure is still largely missing. In this work, a direct measurement of the cation off-centering with respect to the neighboring oxygen is enabled by integrated differential phase contrast (iDPC) imaging, and up to 30 pm Gd off-centering is highly localized at the TB. Further electron energy loss spectroscopy (EELS) analysis demonstrates a slight accumulation of oxygen vacancies at the TB, a self-balanced behavior of Ce at the Gd sites, and a mixed occupation of Fe2+ and Fe3+ at the Fe sites. Our results provide an informative picture with atomic details at the TB of C-GFO, which is indispensable to further push the potential of grain boundary engineering.

Automated summary

With the help of advanced transmission electron microscopy, the researchers have investigated the structure of the (110)-type twin boundary in Ce-doped GdFeO3 (C-GFO) with picometer precision. They have found that the Gd off-centering at the twin boundary is highly localized and can reach up to 30 pm. Furthermore, the analysis using electron energy loss spectroscopy has revealed the presence of oxygen vacancies, self-balanced behavior of Ce, and mixed occupation of Fe2+ and Fe3+ at the twin boundary. This study provides valuable atomic-level information about the twin boundary in C-GFO, which is crucial for further exploration of grain boundary engineering.