Toughening and strengthening zirconia through the addition of a transient solid solution additive

A very small amount of nickel oxide (NiO), 0.18 mol%, could dissolve into yttria-stabilized zirconia (YSZ) during sintering in air at elevated temperature. The presence of Ni solutes enhances both the densification and grain growth of YSZ specimens. By heat-treating the NiO-doped YSZ specimen in a reducing atmosphere, nano-sized Ni particles are produced at the grain boundaries. The NiO thus acts as a transient solid solution additive for the YSZ-Ni nanocomposite. The formation of Ni nano-particles introduces an extra ferromagnetic performance into the YSZ specimen. Furthermore, the toughness and strength of YSZ are enhanced respectively by 120% and 40%. The toughness enhancement shows strong dependence on the size of ZrO2 grains. Nevertheless, the strengthening is contributed by many factors.