Hydrothermal Synthesis, Structure Investigation, and Oxide Ion Conductivity of Mixed Si/Ge-Based Apatite-Type Phases

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dc.contributor.authorLi, HNen_AU
dc.contributor.authorBaikie, Ten_AU
dc.contributor.authorPramana, SSen_AU
dc.contributor.authorShin, J Fen_AU
dc.contributor.authorKeenan, PJen_AU
dc.contributor.authorSlater, PRen_AU
dc.date.accessioned2017-04-26T03:10:45Zen_AU
dc.date.available2017-04-26T03:10:45Zen_AU
dc.date.issued2014-05-02en_AU
dc.date.statistics2016-09-14en_AU
dc.description.abstractApatite-type oxides ([AI4][AII6][(BO4)6]O2), particularly those of the rare-earth silicate and germanate systems, are among the more promising materials being considered as alternative solid oxide fuel cell electrolytes. Nonstoichiometric lanthanum silicate and germanate apatites display pure ionic conductivities exceeding those of yttria-stabilized zirconia at moderate temperatures (500–700 °C). In this study, mixed Si/Ge-based apatites were prepared by hydrothermal synthesis under mild conditions rather than the conventional solid-state method at high temperatures. Single-phase and highly crystalline nanosized apatite powders were obtained with the morphology changing across the series from spheres for the Si-based end member to hexagonal rods for the Ge-based end member. Powder X-ray and neutron analysis found all of these apatites to be hexagonal (P63/m). Quantitative X-ray microanalysis established the partial (<15 at%) substitution of La3+ by Na+ (introduced from the NaOH hydrothermal reagent), which showed a slight preference to enter the AI 4f framework position over the AII 6h tunnel site. Moreover, retention of hydroxide (OH–) was confirmed by IR spectroscopy and thermogravimetric analysis, and these apatites are best described as oxyhydroxyapatites. To prepare dense pellets for conductivity measurements, both conventional heat treatment and spark plasma sintering methods were compared, with the peculiar features of hydrothermally synthesized apatites and the influence of sodium on the ionic conductivity considered.© 2014, American Chemical Society.en_AU
dc.identifier.citationLi, H., Baikie, T., Pramana, S. S., Shin, J. F., Keenan, P. J., Slater, P. R., Brink, F., Hester, J., An, T., & White, T. J. (2014). Hydrothermal synthesis, structure investigation, and oxide ion conductivity of mixed si/ge-cased apatite-type phases. Inorganic Chemistry, 53(10), 4803-4812. doi:10.1021/ic402370een_AU
dc.identifier.govdoc7089en_AU
dc.identifier.issn1520-510Xen_AU
dc.identifier.issue10en_AU
dc.identifier.journaltitleInorganic Chemistryen_AU
dc.identifier.pagination4803-4812en_AU
dc.identifier.urihttp://dx.doi.org/10.1021/ic402370een_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/8626en_AU
dc.identifier.volume53en_AU
dc.language.isoenen_AU
dc.publisherACS Publicationsen_AU
dc.subjectRare earthsen_AU
dc.subjectGermanatesen_AU
dc.subjectElectrolytesen_AU
dc.subjectLanthanumen_AU
dc.subjectZirconiumen_AU
dc.subjectHydrothermal synthesisen_AU
dc.titleHydrothermal Synthesis, Structure Investigation, and Oxide Ion Conductivity of Mixed Si/Ge-Based Apatite-Type Phasesen_AU
dc.typeJournal Articleen_AU
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