WEB Non-transformable tetragonal zirconia based Solid Oxide Cell supports offering high fracture toughness and resistance to isothermal degradationThursday (24.09.2020) 09:00 - 09:15 F: Functional Materials, Surfaces, and Devices 1 Part of:
Metastable (transformable) tetragonal zirconia based ceramics are very tough due to transformation toughening but also susceptible to hydrothermal degradation. The hydrothermal degradation originates from an accelerated tetragonal to monoclinic phase transformation in the presence of water molecules. This phenomenon drastically decreases the mechanical strength of the ceramics. As a result, use of such zirconia compounds in solid oxide fuel and electrolysis cells (for instance in NiO-3YSZ state-of-the-art fuel electrode support, or electrolyte support i.e. 3YSZ) risks the mechanical reliability of the cells. Furthermore, the effect of transformation toughening is known to decrease at high temperatures (800°C) required by the solid oxide cells. In this work, a different class of zirconia materials has been studied, which has a stable tetragonal phase leading to so-called ferroelastic toughening. This was used to manufacture NiO-Zirconia fuel electrode supports. The prepared supports had interestingly high fracture toughness at room temperature (2.6 ± 0.2 MPa m1.2), that was comparable to that of NiO-3YSZ (2.8 MPa m1.2). In addition, the fracture toughness of the new supports did not decrease by increasing temperature, unlike the 3YSZ based supports. Besides, the supports will have excellent resistivity to hydrothermal degradation at room and high temperatures. This class of zirconia materials is thus a promising alternative to the currently used transformable zirconia compounds in solid oxide cell supports.
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