. . . . . . . . . .    ANM 2010     3rd International Conference on Advanced Nano Materials     12-15 September 2010 - Agadir, Morocco Back    Abstract ANMM315 PARTIALLY STABILIZED METASTABLE PHASES OF THE YSZ DOPED WITH ALUMINA  S. Nazarpour 1, C. Zamani 1, C. Lopez 2, F. Ramos 2, A. Cirera 1 1: MIND/IN2UB, Departament d'Electrònica, Universitat de Barcelona. Martí i Franquès 1, Barcelona 08028, Spain 2: Francisco Albero S.A. Rafael Barradas 19, L'Hospitalet de Llobregat 08908, Spain . Appearance of the tetragonal metastable phases in yttria 4.5mol% zirconia (YSZ) was studied. Basically, addition of the yttria into the pure zirconia replaces some of the Zr4+ ions in the zirconia lattice with Y3+ ions. This produces oxygen vacancies, as three O2- ions replace four O2- ions. It also permits yttrium stabilized zirconia to conduct O2- ions, provided there is sufficient vacancy site mobility, a property that increases with temperature. Essentially, alumina and yttria dissolve in zirconia similarly though the interstitial dissolving of alumina is energetically unfavorable. Hence, the solubility limit of alumina into the YSZ is limited and extra alumina particles segregate in the YSZ matrix and grain boundaries. Therefore, the strain energies accumulate around the alumina segregated particles. Basically, high temperature is required providing the ionic conductivity of the YSZ. In this study, it is pointed out that during the cooling process, these strain energies compress the YSZ lattice and generate tetragonal metastable phases. Rapid cooling process magnifies the residual stress around alumina segregated particles and increases the tetragonal metastable phases in the YSZ matrix. Therefore, by modulating the cooling process, the tetragonal metastable phases in YSZ were stabilized. These phases in YSZ are extremely important in the industrial applications due to their excellent resistance to destructive martensitic transformation which is common in large-grained tetragonal phase materials. Besides, its excellent toughness, good strength, and excellent creep resistance make this phase remarkable as well. Because of its properties, the YSZ constructed by tetragonal metastable phases could be ideal for elevated temperature applications such as high temperature fuel cell, gas sensors, heating elements, and the like. . © nanoAC . . . . . . . . . .

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