Enhanced anisotropic ionic diffusion in layered electrolyte structures from density functional theory

Abstract

Electrolytes with high ionic diffusivity at temperatures distinctively lower than the presently used ones are the prerequisite for the success of, e.g., solid oxide fuel cells. We have found a promising structure having an asymmetric but superior ionic mobility in the direction of the oxygen-ion current. Using a layering of zirconium and yttrium in the fluorite structure of zirconia, a high vacancy concentration and a low migration barrier in two dimensions are obtained, while the mobility in the third direction is basically sacrificed. According to our density functional theory calculations an electrolyte made of this structure could operate at a temperature reduced by ≈200 • C. Thus a window to a different class of electrolytes has been flung open. In our structure the price paid is a more complicated manufacturing method.

When two become one: An insight into 2D conductive oxide interfaces

“…Using a model based on the elastic properties of YSZ, Schichtel et al estimated an increase of 2.5 orders of magnitude in the ionic conductivity of YSZ at 7% isotropic tensile strain [107]. By Monte Carlo-based calculations on YSZ, Kushima and Yildiz [108] identified competing processes acting on oxygen diffusivity upon applied strain: for low isotropic tensile strain (up to 4%), oxygen diffusion can increase by 3.8 orders of magnitude at low temperatures due to the fact that the On the other hand, potential strain conditions under which the migration barrier strongly decreases were also identified and simulated for fast anisotropic oxygen diffusion in YSZ [110].…”

Coherency strain and its effect on ionic conductivity and diffusion in solid electrolytes – an improved model for nanocrystalline thin films and a review of experimental data

“…4 In some pioneering studies it was shown that strain may positively influence ionic transport, [5][6][7][8] . In a number of subsequent experimental [9][10][11][12][13][14][15] , theoretical studies [16][17][18][19][20][21][22][23] and a few reviews 4,21,24-26 intrinsic strain as a control parameter has been investigated and even used to tune transport properties in oxide ceramic multilayer microdots. 27 Mostly, epitaxial strain originating at heterophase boundaries was considered, but uniaxially strained single crystals were also studied as well defined model systems.…”

“…Inserting all strain and stress components from eqn (9) to (19) in eqn (20) and performing an integration within the boundaries from x = Àl/2. .…”

Enhanced Oxygen Mobility in Undoped ZrO2–CeO2 Heterostructure

“…In this case, as experimental and theoretical studies show, an increase in ionic conductivity is possible in tensiledeformed lattices, while the opposite effect can be expected as a result of compression deformation. [13][14][15][16][17][19][20][21][22][23][24] The effect of deformation of the crystal lattice on the kinetics of oxygen diffusion was also studied for individual materials, such as zirconium oxide, [25] YSZ, [26][27][28] pure and doped cerium oxide. [29][30][31][32] The obtained results of atomistic modeling indicate that tensile deformation can be used to reduce the barriers to oxygen migration, which ultimately leads to an increase in diffusion.…”

“…The effect of deformation of the crystal lattice on the kinetics of oxygen diffusion was also studied for individual materials, such as zirconium oxide, [ 25 ] YSZ, [ 26–28 ] pure and doped cerium oxide. [ 29–32 ] The obtained results of atomistic modeling indicate that tensile deformation can be used to reduce the barriers to oxygen migration, which ultimately leads to an increase in diffusion.…”