Charged domain walls and crystallographic microstructures in hybrid improper ferroelectric Ca₃ ¹ _xSr_xTi₂O₇

The charged domain walls in ferroelectric materials exhibit intriguing physical properties. We examine herein the charged-domain-wall structures in Ca₃ ¹ _xSr_xTi₂O₇ using transmission electron microscopy. When viewed along the [001] axis, the wavy charged domain walls are observed over a wide range (>5 µm). In contrast, short charged-domain-wall fragments (from 10 to 200 nm long) occur because they are intercepted and truncated by the conventional 180° domain walls. These results reveal the unusual charged domain structures in Ca₃ ¹ _xSr_xTi₂O₇ and will be useful for understanding their formation process.