A Solid Oxide Fuel Cell is a device in which a solid electrolyte is sandwiched between a cathode and an anode. As such, the interface between these different components is very important, as it can affect the materials properties and, therefore, the device’s performance. Furthermore, the lattice mismatch at the interface between different materials has also been recently suggested as a means to improve materials properties, especially the ionic conductivity and oxygen reduction reaction kinetics.

Dislocations are ubiquitous in these materials, and their concentration is high close to an interface. For instance, Chen et al have observed an array of equally spaced dislocations (~ 4 nm) at the interface between yttria-stabilised zirconia and ceria [1]. The role of dislocations on the materials properties is, however, still unclear and an object of controversy. For instance, dislocations have been suggested to either increase [2] or decrease [3] the ionic conductivity of YSZ, without a clear conclusion.

In this paper, we hypothesize that the distribution and mobility of charged defects can change because of the elastic and electrostatic field around dislocations in oxides. We take SrTiO3 as a model perovskite, which is considered to be a promising cathode material when doped with Fe [4] and also used in red-ox based resistive switching memories [5], and assess the impact of dislocation on redistribution and migration of defects by atomistic simulations. By using pair potentials, parameterized with respect to first-principles calculations, we could perform simulations on a fairly extended system (~100,000 atoms). This allowed us to capture one dislocation and to study its effect on the defect chemistry and mobility in this material. The results are rationalized in terms of the strain field around a dislocation.

[1] Chen et al., Applied Physics A 76, 969 (2003)

[2] Sillassen et al., Advanced Functional Materials 20, 2071 (2010)

[3] Li et al., PCCP 15, 1296 (2013)

[4] Jung et al., Advanced Energy Materials 1, 1184 (2011)[5] Waser et al., Advanced Functional Materials 21, 2633 (2011)

Dario Marrocchelli

MIT, Trinity College Dublin

Appearances