Structure evolution of h.c.p./c.c.p. metal oxide interfaces in solid-state reactions

Author(s)
Chen Li, Gerlinde Habler, Thomas Griffiths, Aleksander Rečnik, Petr Jeřábek, L.C. Götze, Clemens Mangler, Timothy Pennycook, Jannik C. Meyer, Rainer Abart
Abstract

The structure of crystalline interfaces plays an important role in solid-state reactions. The Al

2O

3/MgAl

2O

4/MgO system provides an ideal model system for investigating the mechanisms underlying the migration of interfaces during interface reaction. MgAl

2O

4 layers have been grown between Al

2O

3 and MgO, and the atomic structure of Al

2O

3/MgAl

2O

4 interfaces at different growth stages was characterized using aberration-corrected scanning transmission electron microscopy. The oxygen sublattice transforms from hexagonal close-packed (h.c.p.) stacking in Al

2O

3 to cubic close-packed (c.c.p.) stacking in MgAl

2O

4. Partial dislocations associated with steps are observed at the interface. At the reaction-controlled early growth stages, such partial dislocations coexist with the edge dislocations. However, at the diffusion-controlled late growth stages, such partial dislocations are dominant. The observed structures indicate that progression of the Al

2O

3/MgAl

2O

4 interface into Al

2O

3 is accomplished by the glide of partial dislocations accompanied by the exchange of Al

3+ and Mg

2+ cations. The interface migration may be envisaged as a plane-by-plane zipperlike motion, which repeats along the interface facilitating its propagation. MgAl

2O

4 grains can adopt two crystallographic orientations with a twinning orientation relationship, and grow by dislocations gliding in opposite directions. Where the oppositely propagating partial dislocations and interface steps meet, interlinked twin boundaries and incoherent 3 grain boundaries form. The newly grown MgAl

2O

4 grains compete with each other, leading to a growth selection and successive coarsening of the MgAl

2O

4 grains. This understanding could help to interpret the interface reaction or phase transformation of a wide range of materials that exhibit a similar h.c.p./c.c.p. transition.

Organisation(s)
Department of Lithospheric Research, Physics of Nanostructured Materials
External organisation(s)
Jožef Stefan Institute (IJS), Charles University Prague, Freie Universität Berlin (FU), Max-Planck-Institut für Festkörperforschung
Journal
Acta Crystallographica. Section A: Foundation and Advances
Volume
74
Pages
466-480
No. of pages
15
ISSN
0108-7673
DOI
https://doi.org/10.1107/S205327331800757X
Publication date
09-2018
Peer reviewed
Yes
Austrian Fields of Science 2012
103042 Electron microscopy, 105113 Crystallography, 105120 Petrology, 103018 Materials physics
Keywords
ASJC Scopus subject areas
Condensed Matter Physics, Materials Science(all), Structural Biology, Biochemistry, Inorganic Chemistry, Physical and Theoretical Chemistry
Portal url
https://ucris.univie.ac.at/portal/en/publications/structure-evolution-of-hcpccp-metal-oxide-interfaces-in-solidstate-reactions(6c9f4878-866e-43d3-aaf1-e2663f415698).html