Dynamics in Bi(iii)-containing apatite-type oxide ion conductors: a combined computational and experimental study

Abstract

Introduction of Bi(III) into apatite-type germanate oxide ion conductors can improve the conductivity by up to two orders of magnitude. To account for these experimental findings, we have carried out the first ab initio molecular dynamics simulations study of the conduction mechanisms in lone pair-containing apatite-type oxide ion conductors. These calculations were performed on the series La_10−xBi_xGe₆O₂₇ (x = 0, 2, 4) and were supported by neutron scattering experiments. We observe four types of oxide ion exchange mechanisms and describe the effects that the introduction of lone-pair cations has on the O²⁻ migration pathways and on the overall conductivity.