Hole‐Trapping‐Induced Stabilization of Ni4 + in SrNiO3/LaFeO3 Superlattices

Creating new functionality in materials containing transition metals is predicated on the ability to control the associated charge states. For a given transition metal, there is an upper limit on valence that is not exceeded under normal conditions. Here, it is demonstrated that this limit of 3+ for...

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Published in:Advanced materials (Weinheim) 2020-11, Vol.32 (45), p.e2005003-n/a
Main Authors: Wang, Le, Yang, Zhenzhong, Bowden, Mark E., Freeland, John W., Sushko, Peter V., Spurgeon, Steven R., Matthews, Bethany, Samarakoon, Widitha S., Zhou, Hua, Feng, Zhenxing, Engelhard, Mark H., Du, Yingge, Chambers, Scott A.
Format: Article
Language:English
Subjects:
charge transfer
Electrical properties
Fe4
Ferrites
Lanthanum compounds
MATERIALS SCIENCE
Ni4
Nickel
octahedral rotation
Perovskites
Stability
Superlattices
Transition metals
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Summary:Creating new functionality in materials containing transition metals is predicated on the ability to control the associated charge states. For a given transition metal, there is an upper limit on valence that is not exceeded under normal conditions. Here, it is demonstrated that this limit of 3+ for Ni and Fe can be exceeded via synthesis of (SrNiO3)m/(LaFeO3)n superlattices by tuning n and m. The Goldschmidt tolerance constraints are lifted, and SrNi4+O3 with holes on adjacent O anions is stabilized as a perovskite at the single‐unit‐cell level (m = 1). Holding m = 1, spectroscopy reveals that the n = 1 superlattice contains Ni3+ and Fe4+, whereas Ni4+ and Fe3+ are observed in the n = 5 superlattice. It is revealed that the B‐site cation valences can be tuned by controlling the magnitude of the FeO6 octahedral rotations, which, in turn, determine the energy balance between Ni3+/Fe4+ and Ni4+/Fe3+, thus controlling emergent electrical properties such as the band alignment and resulting hole confinement. This approach can be extended to other systems for synthesizing novel, metastable layered structures with new functionalities. The otherwise unstable Ni4+ can be stabilized in perovskite oxides by artificial structuring in carefully designed (SrNiO3)1/(LaFeO3)n superlattices. Spectroscopy measurements in combination with density functional theory calculations reveal that the B‐site cation valences can be tuned by controlling the magnitude of the FeO6 octahedral rotations, which in turn drive the energy balance between Ni3+/Fe4+ and Ni4+/Fe3+, thus controlling emergent electrical properties.
ISSN:0935-9648
1521-4095
DOI:10.1002/adma.202005003