Zirconia is today the compound that presents one of the most diversified application fields as a technical ceramic material. One of the reasons is the multiple allotropic phases of zirconia which suit many different purposes as for example refractive material or additive (high temperature parts), ionic conductor (solid oxide fuel cells), health dentistry), aeronautics (abradables), …. But manufacturing solid zirconia parts require high sintering temperatures (T>1400°C) when using conventional methods.
In the present, great progresses have been made in order to lower the sintering temperature by using different strategies: chemical (dopants, sintering aids), technological (microwave sintering, Spark Plasma Sintering (SPS), flash sintering,…) and/or a combination of both. As an example, combining SPS with the reactivity of hydroxide precursors allowed us to densify at 350°C monoclinic yttria-stabilized zirconia (YSZ). More recently, a strategy based on the combination of Cold Sintering Process (CSP) and SPS made possible to obtain tetragonal YSZ nanostructured ceramics below 900°C by tuning the chemistry through the contribution of a hydrated zirconium carbonate as reactive agent. Now, a narrow temperature window between 850ºC and 950ºC has been identified and investigated in order to sinter YSZ by SPS without reactive agent. In this very sensitive temperature range, the impact of defect chemistry is highlighted both in the densification behavior and in the need for post SPS heat treatment. A subtle combination of experimental parameters (thermal ramps, pressure, environment, ..) has to be found in order to bypass the post-SPS thermal treatment while obtaining dense yttria stabilized zirconia. Understanding the mechanisms based on defect chemistry would allow obtaining high quality YSZ nanostructured ceramics between 850ºC and 950ºC.