Disorder by design: long- and short-range pyrochlore ordering

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dc.contributor.authorMullens, BGen_AU
dc.contributor.authorKennedy, BJen_AU
dc.contributor.authorZhang, ZMen_AU
dc.contributor.authorSaura-Múzquiz, Men_AU
dc.date.accessioned2023-05-05T02:14:32Zen_AU
dc.date.available2023-05-05T02:14:32Zen_AU
dc.date.issued2020-11-11en_AU
dc.date.statistics2023-05-02en_AU
dc.description.abstractCarbon-neutral energy generation is being developed in order to combat climate change. Two technologies of current interest, which are related to renewable and nuclear energy respectively, are next-generation oxygenion conductors for fuel cells and materials suitable for long-term storage and disposal of radioactive nuclear wastes [1-2]. Pyrochlores of the structure A2B2O7 have found immense applications in each of the above areas. Ionic conductors for fuel cells require flexibility and movement in their anionic sublattice, whereas the storage of radioactive nuclear wastes needs a robust lattice from which ions cannot escape. This is a seemingly contradiction in requirements. It is believed that the oxygen vacancies present in the pyrochlore structure allow for the development of short-range disorder, whilst keeping the long-range order intact [3]. The pyrochlore structure can be viewed as a superstructure of the defect-fluorite structure. The defect-fluorite structure (A2BO5) consists of a random distribution of cations and oxygen vacancies. However, by choosing A and B with a particular ionic radii ratio, the ordered pyrochlore superstructure may form under ambient conditions. This ordering of oxygen vacancies may be analysed using neutron powder diffraction and used to reason the enhanced properties and applications of pyrochlores [4]. The current work aims to characterise oxygen-vacancy disorder in defect pyrochlores so to enable the rational design of defect pyrochlores that are optimised for specific applications. We have done this by looking at ‘stuffed’ pyrochlores of the form A2(B2−xAx)O7−x/2 where the smaller B-type cation, in this case Ti4+, is progressively replaced by a larger A-type cation (Tm3+). We wish to determine whether controlling the disorder in the cation sublattice will allow us to tailor-make stuffed pyrochlores targeting specific applications across ionic conductivity, magnetism, photocatalysis and the storage of long-term radioactive waste. Series of stuffed pyrochlores have been synthesised using conventional solid-state methods and their longrange average structures characterised by Rietveld refinement against combined neutron and synchrotron X-ray diffraction data. The local short-range order has been characterised by Raman spectroscopy and XANES. Other measurements have also been performed regarding their applications, demonstrating a vast improvement in their ionic conductivity at high temperatures. These results will be presented, along with a judgement as to whether inducing certain types of disorder within the pyrochlore structure can lead to them being purposely engineered for specific applications. © 2020 The Authorsen_AU
dc.identifier.citationMullens, B., Kennedy, B., Zhang, Z., & Saura-Múzquiz, M. (2020). Disorder by design: long- and short-range pyrochlore ordering. Paper presented to the ANBUG-AINSE Neutron Scattering Symposium, AANSS 2020, Virtual Meeting, 11th - 13th November 2020, (pp. 96). Retrieved from: https://events01.synchrotron.org.au/event/125/attachments/725/1149/AANSS_Abstract_Booklet_Complete_-_1_Page_Reduced.pdfen_AU
dc.identifier.conferenceenddate13 November 2020en_AU
dc.identifier.conferencenameANBUG-AINSE Neutron Scattering Symposium, AANSS 2020en_AU
dc.identifier.conferenceplaceVirtual Meetingen_AU
dc.identifier.conferencestartdate11 November 2020en_AU
dc.identifier.pagination96en_AU
dc.identifier.urihttps://events01.synchrotron.org.au/event/125/contributions/3771/contribution.pdfen_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/15011en_AU
dc.language.isoenen_AU
dc.publisherAustralian Institute of Nuclear Science and Engineering (AINSE)en_AU
dc.subjectCarbonen_AU
dc.subjectEnergyen_AU
dc.subjectRadioactive wastesen_AU
dc.subjectFuel cellsen_AU
dc.subjectOxygenen_AU
dc.subjectX-ray diffractionen_AU
dc.subjectSpectroscopyen_AU
dc.subjectANSTOen_AU
dc.subjectMaterialsen_AU
dc.subjectDataen_AU
dc.subjectPyrochloreen_AU
dc.titleDisorder by design: long- and short-range pyrochlore orderingen_AU
dc.typeConference Abstracten_AU
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