The atomic structure and chemistry of Fe-rich steps on antiphase boundaries in Ti-doped Bi0.9Nd0.15FeO3

Ian Maclaren,Bernhard Schaffer,Quentin M Ramasse,Ian M Reaney,Kambiz Kalantari,Alan J Craven,Liqiu Wang

doi:10.1063/1.4884684

Abstract

Stepped antiphase boundaries are frequently observed in Ti-doped Bi0.85Nd0.15FeO3, related to the novel planar antiphase boundaries reported recently. The atomic structure and chemistry of these steps are determined by a combination of high angle annular dark field and bright field scanning transmission electron microscopy imaging, together with electron energy loss spectroscopy. The core of these steps is found to consist of 4 edge-sharing FeO6 octahedra. The structure is confirmed by image simulations using a frozen phonon multislice approach. The steps are also found to be negatively charged and, like the planar boundaries studied previously, result in polarisation of the surrounding perovskite matrix.

Highlights

It has been previously shown that Ti-doping in Bi0.9Nd0.15FeO3 suppresses conductivity via a donor doping mechanism and allows the ferroelectric and antiferroelectric phase transitions to be directly observed in temperature dependent dielectric data.[1]
These antiphase boundaries (APBs) have a core held together with edge-sharing octahedra, one of which is always a TiO6 octahedron. Their chemical structure was reconstructed at 10 pm precision in 3 dimensions and it was shown that the core had excess negative charge which resulted in a strong polarisation of the surrounding perovskite and the stabilisation of a polar phase a few unit cells each side of the APB.[4]
We restricted the discussion to planar sections of the boundaries on the (001) plane. We show that such antiphase boundaries can deviate strongly from the {001} planes through the formation of stepped structures

Summary

Introduction

It has been previously shown that Ti-doping in Bi0.9Nd0.15FeO3 suppresses conductivity via a donor doping mechanism and allows the ferroelectric and antiferroelectric phase transitions to be directly observed in temperature dependent dielectric data.[1]. The atomic structure and chemistry of Fe-rich steps on antiphase boundaries in Tidoped Bi0.9Nd0.15FeO3

Results

Conclusion