title: Direct mapping of Li-enabled octahedral tilt ordering and associated strain in nanostructured perovskites.
abstract: Self-assembled nanostructures with periodic phase separation hold great promise for creating two- and three-dimensional superlattices with extraordinary physical properties. Understanding the mechanism(s) driving the formation of such superlattices demands an understanding of their underlying atomic structure. However, the nanoscale structural fluctuations intrinsic to these superlattices pose a new challenge for structure determination methods. Here we develop an optimized atomic-level imaging condition to measure TiO6 octahedral tilt angles, unit-cell-by-unit-cell, in perovskite-based Li(0.5-3x)Nd(0.5+x)TiO3, and thereby determine the mathematical formula governing this nanoscale superstructure. We obtain a direct real-space correlation of the octahedral tilt modulation with the superstructure geometry and lattice-parameter variations. This reveals a composition-dependent, self-ordered octahedral superlattice. Amazingly, we observe a reversible annihilation/reconstruction of the octahedral superlattice correlated with the delithiation/lithiation process in this promising Li-ion conductor. This approach to quantify local octahedral tilt and correlate it with strain can be applied to characterize complex octahedral behaviours in other advanced oxide systems.
authors: Department of Materials Science and Engineering, Monash University, Victoria 3800, Australia.
authors: Ye
authors: Y
authors: Zhu
authors: Research School of Chemistry, College of Physical and Mathematical Sciences, The Australian National University, Canberra, Australian Capital Territory 0200, Australia.
authors: Ray L
authors: RL
authors: Withers
authors: Department of Materials Science and Engineering, Monash University, Victoria 3800, Australia.|Monash Centre for Electron Microscopy, Monash University, Victoria 3800, Australia.
authors: Laure
authors: L
authors: Bourgeois
authors: Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.
authors: Christian
authors: C
authors: Dwyer
authors: Department of Materials Science and Engineering, Monash University, Victoria 3800, Australia.|Monash Centre for Electron Microscopy, Monash University, Victoria 3800, Australia.
authors: Joanne
authors: J
authors: Etheridge