Browsing by Author "Cui, X"

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    The structure of yttria-stabilised zirconia: a combined medium energy photoemission and ab-initio investigation
    (Australian Institute of Physics, 2011-02-01) Cousland, GP; Wong, L; Tayebjee, M; Yu, DH; Triani, G; Stampfl, APJ; Cui, X; Stampfl, CM; Smith, AE
    Cubic zirconia-based materials are candidates for use in the nuclear fuel cycle. There are three phases of ZrO2, a room temperature monoclinic phase and higher temperature tetragonal and cubic phases. The cubic phase of zirconia, in comparison to the other phases, exhibits a very low thermal conductivity, allowing the material to be potentially used in high temperature fission and fusion environments. Interestingly, the cubic-phase may be stabilised at room temperature through the addition of small quantities of other oxides for example, Y2O3, CaO and Ce2O3. Recent ab initio calculations for yttria-stablised zirconia (YSZ) predict the atomic geometry for various oxygen-vacancy containing structures [1]. In particular, a set of “rules” is used to establish a structure for 6.25 Mol % [1,2]. This model is extended to a yttria content of 9.375 Mol % and compared with a sample of 9.5 Mol % yttria. Using this model, core-level shifts are estimated as changes in binding energy obtained from density-functional theory (DFT) calculations, due to the different chemical environments. The partial density-of-states of Y atoms differ depending upon whether there are oxygen vacancies at nearest-neighbour sites to the Zr atoms. Experimentally, a number of different core-levels and Auger-lines are acquired across the L-edges of Zr and Y. By measuring through the Y Ledge resonance, three distinct Zr environments and three distinct oxygen environments are observed in photoelectron peaks. The area under each peak is plotted against photon energy.