Structural studies on the optimisation of fast oxide ion transport

Extensive regions of cubic fluorite solid solution formation are observed i n the Y2O3-ZrO2, Y2O3-ZrO2-TiO2 and Y2O3-ZrO2-Nb2O5 systems. Ionic conducti vity studies indicate that the activation energy for conduction increases r apidly whilst the high temperature conductivity decreases as yttria-content increases. At high defect concentrations, however, activation energies ten d towards a constant value. The increase in activation energy correlates wi th an increase in the extent of diffuse reflections in neutron diffraction experiments and with increases in the isotropic temperature factor associat ed with the anion sublattice. Significant negative correlation was observed between conductivity prefactor and oxygen temperature factors. Electron di ffraction experiments also show diffuse elements in addition to the cubic f luorite structure, indicating the presence of short-range order related to C-type and distorted pyrochlore types, (C) 2000 Elsevier Science B.V. All r ights reserved.