Characterising oxygen diffusion in scheelites La(Nb,Mo)O4+δ

Oxide ion conductors are key components in several technologically important applications, including solid oxide fuel cell (SOFC) devices to allow the safe conversion of hydrogen fuel into energy. The scheelite material LaNbO4 exhibits moderate oxide ion conductivity that is greatly enhanced by the partial replacement of niobium with molybdenum (up to 20%); this also introduces excess interstitial oxide ions into the crystal lattice. The aim of this proposal is to shed light on the atomic-scale processes involved in oxide ion conductivity in scheelites, as well the effects of increasing Mo (and interstitial oxide) content on this behaviour. Quasielastic neutron scattering measurements of La(Nb,Mo)O4+d samples containing 0%, 8% and 20% Mo will allow us to determine the rate and activation energy of oxygen motions at high temperatures, which we will relate to their structure and chemistry.

氧化物离子导体是多项关键技术应用的核心组分，其中包括可实现氢气燃料安全转化为电能的固体氧化物燃料电池（solid oxide fuel cell, SOFC）装置。白钨矿型材料LaNbO4具备适中的氧化物离子导电率，当用钼（Mo）部分取代其中的铌（Nb）（取代比例最高可达20%）时，其导电率会得到显著提升；同时该取代过程还会向晶体晶格中引入过量的间隙氧化物离子。本研究的目标是阐明白钨矿材料中氧化物离子导电相关的原子尺度过程，以及钼（以及间隙氧化物离子）含量提升对该导电行为的影响。对含钼量分别为0%、8%和20%的La(Nb,Mo)O4+δ样品开展准弹性中子散射（quasielastic neutron scattering）测试，可帮助我们测定高温下氧原子运动的速率与活化能，并将该结果与样品的结构与化学性质相关联。