Structure evolution of h.c.p./c.c.p. metal oxide interfaces in solid‐state reactions. Issue 5 (8th August 2018)

• Record Type: Journal Article
• Authors: Li, C.; Habler, G.; Griffiths, T.; Rečnik, A.; Jeřábek, P.; Götze, L. C.; Mangler, C.; Pennycook, T. J.; Meyer, J.; Abart, R.
• Is Part Of: Acta crystallographica. Volume 74:Issue 5(2018:Sep.)
• Page Start: 466
• Page End: 480
• Publication Date: 2018-08-08
• Subjects: interface migration -- partial dislocations -- aberration‐corrected STEM -- h.c.p./c.c.p. (h.c.p./f.c.c.) lattices -- dislocation glide; Crystallography -- Periodicals; Condensed matter -- Periodicals; 548
• DOI: 10.1107/S205327331800757X
• Languages: English
• ISSNs: 2053-2733

Abstract

Abstract : The atomic structure of Al2 O3 /MgAl2 O4 interfaces at different growth stages is revealed by scanning transmission electron microscopy. Partial dislocations in the hexagonal close‐packed/cubic close‐packed oxygen sublattices become increasingly dominant as the growth proceeds, suggesting a dislocation glide mechanism in the late growth stage. Abstract : The structure of crystalline interfaces plays an important role in solid‐state reactions. The Al2 O3 /MgAl2 O4 /MgO system provides an ideal model system for investigating the mechanisms underlying the migration of interfaces during interface reaction. MgAl2 O4 layers have been grown between Al2 O3 and MgO, and the atomic structure of Al2 O3 /MgAl2 O4 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 Al2 O3 to cubic close‐packed (c.c.p.) stacking in MgAl2 O4 . 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 Al2 O3 /MgAl2 O4 interface into Al2 O3 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 zipper‐like motion, which repeats along the interface facilitating its propagation. MgAl2 O4 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 Σ3 grain boundaries form. The newly grown MgAl2 O4 grains compete with each other, leading to a growth selection and successive coarsening of the MgAl2 O4 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.