Ionic conductivity in oxide heterostructures: the role of interfaces

Abstract

Rapidly growing attention is being directed to the investigation of ionic conductivity in oxide film heterostructures. The main reason for this interest arises from interfacial phenomena in these heterostructures and their applications. Recent results revealed that heterophase interfaces have faster ionic conduction pathways than the bulk or homophase interfaces. This finding can open attractive opportunities in the field of micro-ionic devices. The influence of the interfaces on the conduction properties of heterostructures is becoming increasingly important with the miniaturization of solid-state devices, which leads to an enhanced interface density at the expense of the bulk. This review aims to describe the main evidence of interfacial phenomena in ion-conducting film heterostructures, highlighting the fundamental and technological relevance and offering guidelines to understanding the interface conduction mechanisms in these structures.

Termination chemistry-driven dislocation structure at SrTiO3/MgO heterointerfaces

“…Oxygen vacancies, typically positively charged in similar oxides 39,40 , lead to electrostatic interactions that alter the energetics of vacancies nearby. Furthermore, the formation of equilibrium space-charge regions 7,39,41,42 at the interface can lead to vacancy-rich dislocation cores and vacancy-depleted spacecharge zones, which would further influence the oxygen vacancy energy and defect concentration. In addition, either oxygen-rich or oxygen-poor conditions 43 encountered during deposition would have a bearing on the oxygen vacancy energies.…”

“…48). In addition, as oxide nanocomposites are increasingly used in solid oxide fuel cells and oxygen separation membranes 7 , the TiO 2 -terminated interface can serve as a model system for assessing the role of pipe diffusion for conductivity, as observed in yttria-stabilized zirconia 49 . In contrast, the SrOterminated interface does not exhibit such behaviour, with vacancies concentrated in terraces separated by dislocations that act as barriers for migration.…”

“…T he last decade has witnessed unabated growth of research on oxide materials due to their wide-ranging applications that include information storage [1][2][3] , radiation-tolerant materials 4,5 , fuel cells 6,7 and batteries 8 . In the majority of these applications, vital properties of nanocomposite oxides are influenced or even controlled by oxide interfaces.…”

Ab initioinvestigation of defect formation at ZrO2-CeO2interfaces

“…Recently, the fabrication and characterization of highly conductive ionic thin-film electrolytes has taken a new direction, due to the observed enhancement of ionic conductivity in ionic hetero-structures. 7,8 Major interest was raised by the huge increase of ionic conductivity reported by Garcia-Barriocanal et al 9 for a multilayered heterojunction made of ZrO 2 -Y 2 O 3 /SrTiO 3 . However, the nature of charge carriers has been questioned and hypothesized to be electronic rather than ionic.…”

Cerium reduction at the interface between ceria and yttria-stabilised zirconia and implications for interfacial oxygen non-stoichiometry

“…[7][8][9][10][11] Previous investigations suggested different possible explanations of the interfacial effects such as misfit dislocations, segregations of dopants, strain, and space charge regions. 12,13 However, possible mechanisms for the enhanced ionic conductivity in CeO 2 /YSZ hetero-structures are still under discussion. Since interface atomic structures and chemistry are deemed to play crucial roles, it is key to microscopically investigate defined CeO 2 /YSZ interfaces, in order to be able to improve the transport properties of these hetero-structured systems.…”