The role of disconnections in redox-induced phase transformation of metal oxides
Abstract
Detailed atomic-level understanding of the phase transformation between magnetite (Fe3 O4) and haematite (Fe2 O3) is lacking, despite widespread interest in redox reactions of metal oxide systems. While the magnetite-to-haematite transformation entails the addition of oxygen to the system and thus a net diffusive flux, haematite formations have been reported to grow along well-defined habits on the close-packed {0001}Fe2 O3//{111}Fe3 O4 planes. The propagation of the phase interface in the bulk is thus thought to maintain the oxygen sublattice fixed up to a shear, and to require long-range diffusion of iron ions. In this letter we propose interfacial steps with dislocation character, i.e. disconnections, as the elementary defects propagating the transformation. We use the topological model of interfacial defects to predict three disconnection modes for the system, and we employ scanning transmission electron microscopy to ascertain their presence in a haematite/magnetite interface of a partially oxidised magnetite powder. Using atomistic simulations, we determine the equilibrium structures of the disconnections, and study their motion and how they accomplish the transformation, obtaining excellent agreement with atomic-resolution experimental observations.
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BibTeX
@misc{ruffino2026role,
title = {{The role of disconnections in redox-induced phase transformation of metal oxides}},
author = {Martina Ruffino and Baptiste Bienvenu and Xuyang Zhou and Dierk Raabe and Yan Ma},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.18446},
eprint = {2609.18446},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.18446},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The role of disconnections in redox-induced phase transformation of metal oxides
AU - Martina Ruffino
AU - Baptiste Bienvenu
AU - Xuyang Zhou
AU - Dierk Raabe
AU - Yan Ma
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.18446
UR - https://arxiv.org/abs/2609.18446
AB - Detailed atomic-level understanding of the phase transformation between magnetite (Fe_3 O_4) and haematite (Fe_2 O_3) is lacking, despite widespread interest in redox reactions of metal oxide systems. While the magnetite-to-haematite transformation entails the addition of oxygen to the system and thus a net diffusive flux, haematite formations have been reported to grow along well-defined habits on the close-packed {0001}_Fe_2 O_3//{111}_Fe_3 O_4 planes. The propagation of the phase interface in the bulk is thus thought to maintain the oxygen sublattice fixed up to a shear, and to require long-range diffusion of iron ions. In this letter we propose interfacial steps with dislocation character, i.e. disconnections, as the elementary defects propagating the transformation. We use the topological model of interfacial defects to predict three disconnection modes for the system, and we employ scanning transmission electron microscopy to ascertain their presence in a haematite/magnetite interface of a partially oxidised magnetite powder. Using atomistic simulations, we determine the equilibrium structures of the disconnections, and study their motion and how they accomplish the transformation, obtaining excellent agreement with atomic-resolution experimental observations.
ER -