Effect of an external electric field on the diffusion of oxygen ions in zirconium dioxide doped with yttrium oxide. Molecular dynamics study

Abstract

The influence of an external electric field on the character of ion motion, diffusion coefficients, and diffusion activation energies in cubic ZrO2 doped with Y2O3 with varying dopant content, temperature, and electric field strength has been studied by the molecular dynamics method. The diffusion coefficient of oxygen vacancies for models with different Y2O3 contents in the temperature range 873–1273 K without an imposed field decreases with an increase in the molar fraction of yttrium oxide in the crystal, while the dependence of the diffusion coefficient of O2− ions has a maximum (2.4∙10−11 m2/s) with an yttrium oxide content of 3 mol%. The activation energy of ionic conductivity, estimated in the absence of a field on the basis of diffusion of O2− ions, increases from 0.45 eV at a Y2O3 content of 4.6 mol% to 0.61 eV at a dopant content of 15.7 mol%. An external electric field of 0.02–0.08 V/Å noticeably changes the frequency of jumps of oxygen ions. At the electric field strength of 0.08 V/Å, a dopant content of 4.6 mol%, and a temperature of 1073 K, the О2− diffusion coefficient increases to 1.41∙10−9 m2/s. The dependence of diffusion coefficients on the field strength is close to quadratic.