Influence of interface structure on mass transport in phase boundaries between different ionic materials

Abstract

Internal and external interfaces in solids exhibit completely different transport properties compared to the bulk. Transport parallel to grain or phase boundaries is usually strongly enhanced. Transport perpendicular to an interface is usually blocked, i.e., transport across an interface is often much slower. Due to the high density of interfaces in modern micro- and nanoscaled devices, a severe influence on the total transport properties can be expected. In contrast to diffusion in metal grain boundaries, transport phenomena in boundaries of ionic materials are still less understood. The specific transport properties along metal grain boundaries are explained by structural factors like packing densities or dislocation densities in the interface region. In most studies dealing with ionic materials, the interfacial transport properties are merely explained by the influence of space charge regions. In this study the influence of the interface structure on the interfacial transport properties of ionic materials is discussed in analogy to metallic materials. A qualitative model based on the density of misfit dislocations and on interfacial strain is introduced for (untilted and untwisted) phase boundaries. For experimental verification, the interfacial ionic conductivity of different multilayer systems consisting of stabilised ZrO2 and an insulating oxide is investigated as a funtion of structural mismatch. As predicted by the model, the interfacial conductivity increases when the lattice mismatch is increased.Graphical abstract

Tensile Lattice Distortion Does Not Affect Oxygen Transport in Yttria-Stabilized Zirconia–CeO2 Heterointerfaces

“…This material is available free of charge via the Internet at http://pubs.acs.org. The sample is gold coated with a region masked off, as shown schematically in (a), the sample is exposed to an 18 O enriched atmosphere allowing 16 O- 18 O exchange solely at the trench edge. The gold capping layer is then removed allowing SIMS analysis (b) resulting in a 3-dimensional dataset (c), which can be separated into layer types.…”

“…7,10,[12][13][14][15][16] Polycrystalline 9.5YSZ-Y 2 O 3 multilayered films {(0001) Al 2 O 3 |Y 2 O 3 | (9.5YSZ|Y 2 O 3 ) x n} grown on sapphire substrates with (quasi-)coherent hetero-interfaces along each columnar grain showed that the conductivity slightly increased and the activation energy slightly decreased with increasing the number of interfaces 10 . According to the authors, the grain boundary conduction pathway played a negligible role in the charge transport.…”

Anomalous Oxidation States in Multilayers for Fuel Cell Applications

“…Experimental observations of increased ionic conductivities have been reported for highly oriented epitaxial structures of several electrolyte materials such as YSZ, [2,13] Sm 2 O 3 -doped CeO 2 , [5,9] and YSZ/SrTiO 3 heterostructures. [14] In these materials the conductivity is viewed as being enhanced through engineering of the interfaces, rather than manipulation of the bulk chemical composition.…”

“…Korte [13] and co-workers have investigated the effects of elastic strain at heterojunctions in highly substituted oxide systems, where space charge effects can be negligible, and have concluded that conductivity can be both enhanced and depressed by the effects of elastic strain at the interfaces.…”

Ionic conductivity in oxide heterostructures: the role of interfaces

“…Korte and co-workers provided a comprehensive description of the effect of structural mismatch on the interface conduction [31][32][33][34]. Depending on the mismatch degree between the two adjacent phases, the interface can be classified as coherent, semicoherent or incoherent.…”