Vacancy ordering effects on the conductivity of yttria- and scandia-doped zirconia

TL;DR

This study uses molecular dynamics with ab initio parametrized potentials to analyze how vacancy ordering affects conductivity in yttria- and scandia-doped zirconia, revealing intrinsic vacancy interactions limit maximum conductivity.

Contribution

It demonstrates the impact of vacancy-vacancy and vacancy-cation interactions on conductivity, highlighting the potential of scandia-doped zirconia for high conductivity applications.

Findings

Maximum conductivity occurs at 8-13% dopant concentration.

Scandia-doped zirconia shows weaker vacancy interactions, indicating higher potential conductivity.

Intrinsic vacancy-vacancy interactions limit conductivity regardless of dopant choice.

Abstract

Polarizable interaction potentials, parametrized using ab initio electronic structure calculations, have been used in molecular dynamics simulations to study the conduction mechanism in Y2 O3 - and Sc2 O3 -doped zirconias. The influence of vacancy-vacancy and vacancy-cation interactions on the conductivity of these materials has been characterised. While the latter can be avoided by using dopant cations with radii which match those of Zr4+ (as is the case of Sc3+), the former is an intrinsic characteristic of the fluorite lattice which cannot be avoided and which is shown to be responsible for the occurrence of a maximum in the conductivity at dopant concentrations between 8 and 13 %. The weakness of the Sc-vacancy interactions in Sc2 O3 -doped zirconia suggests that this material is likely to present the highest conductivity achievable in zirconias.