Molecular dynamics simulations of oxygen diffusion in GdBaCo2O5.5

Abstract

International audienceThe mechanisms of oxygen diffusion in GdBaCo2O5.5 compound are investigated by molecular dynamics simulations. The results confirm that diffusion is mainly bidimensional with oxygen moving in the a,b plane while diffusion along the c axis is much more difficult. Between 1000 and 1600 K, the activation energy for diffusion is about 0.6 eV, close to experimental values. Going deeper inside the oxygen diffusion mechanism, we see that this diffusion occurs mainly in the cobalt planes while most of the oxygen vacancies are kept in the Gd planes. Analysis of oxygen motions show that Gd planes can be seen as source-sink for the oxygen vacancies rather than as fast pathways

Molecular dynamics analysis of lattice site dependent oxygen ion diffusion in YBa2Cu3O7−δ: Exposing the origin of anisotropic oxygen diffusivity

“…7. For low temperatures, the ratio of D a(b) /D c for oxygen ions on Cu-O chains is evidently larger than 1, which is comparable to the value of D a(b) /D c for the oxygen diffusion in GdBaCo 2 O 5.5 due to similar layer-by-layer perovskite structure [5]. As temperature increases, D a(b) /D c decreases significantly and approaches to unity (Fig.…”

“…This explanation, however, belies a large complexity which requires more detailed investigation. Inspired by the recent MD studies of the anisotropic oxygen diffusion in other perovskite compounds [3][4][5], we examine the projection of oxygen MSD in YBCO along the three orthogonal directions, i.e., the directions along the a, b, and c-axes. The directional MSD of oxygen ions at different lattice sites is plotted as a function of time in Fig.…”

“…Nevertheless, these work rarely considered the lattice diffusion of oxygen in YBCO. Moreover, the oxygen density plots for some oxides in the recent MD analysis show that the oxygen diffusion may have distinct preferential directions on different lattice sites [3][4][5], which also reveal that the lattice diffusion of oxygen ions is far more complex than has been recognized so far. Although the oxygen diffusion in YBCO has been studied numerically [29], the peculiarities of oxygen diffusivity at each different lattice site in YBCO are lacking and need to be well studied.…”

“…Attention has therefore focused on the diffusivity of oxygen in solid state oxides [3][4][5][6][7][8][9][10][11]. Some high temperature superconductors, such as yttrium-barium cuprate (YBa 2 Cu 3 O 7−δ or YBCO), with quite promising superconductive and magnetic properties [12,13], are one case where both the oxide crystal growth and phase transitions are highly sensitive to oxygen diffusion.…”

Impact of doping on the ionic conductivity of ceria: A comprehensive model

“…5,6 Presently, there are numerous candidate oxides which are considered for cathode and electrolyte applications for the next generation of intermediate temperature solid oxide fuel cells. [7][8][9][10][11][12] In previous studies of reduced CeO 2 , 13 charge transport was demonstrated to be achieved by a hopping process of O vacancies and the related distortions. This mechanism is in agreement with the O defect model established by careful measurements of the electrical conductivity of reduced CeO 2 as a function of temperature and O 2 pressure in Ref.…”