Effects of fine alumina dispersion on ionic conductivity and mechanical properties of ytterbia stabilized cubic zirconia

Nanocomposites of Yb2O3 stabilized ZrO2 (YbSZ) containing fine Al2O3 dispersions were fabricated by conventional powder mixing and a pressureless sintering technique. A fine homogeneous microstructure was obtained for the composites. This microstructural refinement decreased the size of defects in the composites, which significantly increased the fracture strength of the composites compared to that of monolithic ZrO2. The composites had the same ionic conductivity values as those of the monolithic ceramics at high temperatures (in the range of 800-1000degreesC). Furthermore, the activation energy at high temperatures was independent of the Al2O3 content, whereas in the lower temperature regime (300-800degreesC), it varied with the Al2O3 fraction. This indicated that different O2- conduction-based activation processes were operating in the two temperature regimes. The O2- ion transfer could easily occur at high temperatures due to the presence of the Al2O3 particulate dispersion in the composite system. From these results, it was concluded that the dispersion of fine grained Al2O3 into YbSZ is advantageous for achieving high-strength ion-conductive cubic zirconia.