Novel yttria-stabilised zirconia–alumina tetragonal phase obtained by co-precipitation

Yttria-stabilised zirconia–alumina (YSZ–A) compounds, 9010,8020,7030and6040wt%, were obtained by the co-precipitation route. Among them, a novel tetragonal phase, 90 wt% of 3 mol% YSZ and 10 wt% of Al2O3, was obtained. Phase identification was carried out by X-ray diffraction (XRD). For structural studies, XRD data were analysed by Rietveld refinements. This novel phase, with lattice parameters a=5.09964Å and c=5.17488Å, may be associated with a distorted polyhedron of a cubic ZrO2 structure obtained by partial substitution of Y3+ and Al3+ cations at Zr4+positions. Particle size, which was determined by transmission electron microscopy, ranges from 50 to 100 nm. Conductivity measurements, by impedance spectroscopy, showed a good ionic conductor material with similar properties of those of pure zirconia. Quantum mechanics molecular simulation determined the electron properties of the corresponding crystal. This allowed establishing the density of states, which implies important differences to the reported tetragonal phases.