Elastic strain at interfaces and its influence on ionic conductivity in nanoscaled solid electrolyte thin films—theoretical considerations and experimental studies

Abstract

Ionic transport in solids parallel to grain or phase boundaries is usually strongly enhanced compared to the bulk. Transport perpendicular to an interface (across an interface) is often much slower. Therefore in modern micro- and nanoscaled devices, a severe influence on the ionic/atomic transport properties can be expected due to the high density of interfaces.Transport processes in boundaries of ionic materials are still not understood on an atomic scale. In most of the studies on ionic materials the interfacial transport properties are explained by the influence of space charge regions. Here we discuss the influence of interfacial strain at semicoherent or coherent heterophase boundaries on ionic transport along these interfaces in ionic materials. A qualitative model is introduced for (untilted and untwisted) hetero phase boundaries. For experimental verification, the interfacial oxygen ionic conductivity of different multilayer systems consisting of cubic ZrO(2) stabilised by aliovalent dopands (YSZ, CSZ) and an insulating oxide is investigated as a function of structural mismatch. Recent results on extremely fast ionic conduction in YSZ/SrTiO(3) thin film systems ("colossal ionic concuctivity at interfaces") is discussed from the viewpoint of strain effects.

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

“…In general, literature data are quite consistent concerning the increased oxygen-ion conductivity of interfaces showing a large dislocation density, 4,7,9 but whether the interfacial strain can play a significant role in enhancing the ionic conductivity is still quite a controversial issue.…”

“…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.…”

Mechanism for enhanced oxygen reduction kinetics at the (La,Sr)CoO3−δ/(La,Sr)2CoO4+δ hetero-interface

“…As shown in (by works including that of the authors here) to have a significant impact on facilitating oxygen ion transport, [24][25][26][27][28] vacancy formation, [29][30][31][32] and surface adsorption 27, 30 -specific to this paper's scope are the oxygen vacancy formation, oxygen adsorption and oxygen incorporation kinetics on the (La,Sr)CoO 3 films. 27,30,33 La 2 CoO 4+δ has not been a subject of similar studies to date, and we address the potential effects of strain also in this material as part of this paper.…”

Chemomechanics of ionically conductive ceramics for electrical energy conversion and storage

“…Schichtel et al used a combination of theoretical considerations and experimental data to investigate the effect of elastic strain on ionic conductivity at coherent interfaces between YSZ and insulating oxides [187]. Figure 10 illustrates their result that the conductivity was enhanced by less than a factor of two at 3 % and 4 % lattice mismatch, though the exact strain state of the films was not reported.…”

“…10 Yttria-stabilized zirconia exhibits ionic conductivity that some researchers have found to correlate with elastic strain at coherent interfaces with insulating oxides. Reproduced from Ref [187] with permission of the PCCP Owner Societies to 12 nm [188]. Pergolesi et al fabricated YSZ/CeO 2 multilayer samples with varying numbers of heterointerfaces with minimal interfacial dislocation densities [189].…”