First-principles study and modeling of strain-dependent ionic migration in ZrO2

Abstract

Electrolytes with high ionic conductivity at lower temperatures are the prerequisite for the success of Solid Oxide Fuel Cells (SOFC). One promising candidate is doped zirconia. In the past its ionic conductivity has mainly been increased by decreasing its thickness. However, the influence of the thickness is only linear, whereas the impact of migration barriers is exponential. Therefore understanding the oxygen transport in doped zirconia is of fundamental importance. In this work we pursue the approach of the strain dependent ionic migration in zirconia. We investigate how the migration barriers for oxygen ions respond to a change of the atomic strain. We employ the method of Density Functional Theory (DFT) calculations to relax the atomic configurations to the ground state. In connection with the Nudged Elastic Band (NEB) method we obtain the migration barrier of the oxygen ion jumps in zirconia for a given lattice constant. Similar to other publications we observe a decrease in the migration barrier for expansive strain, but in addition we also find a migration barrier decrease for high compressive strains beyond a maximal height of the migration barrier at an intermediate compressive strain. We present a simple analytic model which, by using interactions of the Lennard-Jones type, gives an explanation for this behavior.

The detailed geometrical and electronic structures of monoclinic zirconia

“…Recently, first-principle calculations have been used to investigate the configuration and stability of the point defects in ZrO 2 [27][28][29], the hydrogen oxidation reactions at the Ni/ZrO 2 interface [30,31], strain-dependent ionic migration in ZrO 2 [32] and ZrO 2 nanosheets and nanotubes [33].…”

Discovery of zirconium dioxides for the design of better oxygen-ion conductors using efficient algorithms beyond data mining

“…We summarize the E m values of the Fm 3m and the P4 2 /nmc structures obtained herein and in former computational studies 42,[47][48][49][50] in Table 5. Former computational studies have mainly used the GGA, rather than the GGA+U.…”

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.…”