Yttria-stabilized zirconia (8YSZ) synthesis in a supercritical CO2-assisted process: a parametric study for achieving cubic phase stability

Abstract

Yttria-stabilized zirconia (YSZ) with a yttria content beyond 8%_mol is especially interesting for its high ionic conductivity in the high-temperature range (700–1000 °C). Thereby, cubic YSZ properties make it a useful ceramic material for electrodes or electrolytes in various applications, such as solid oxide cell (SOC) technologies for energy conversion or oxygen sensors. This work aims to propose an alternative microstructure, hopefully, to improve material features. Adapting a sol–gel-type process that involves the use of supercritical CO₂ (scCO₂) to stabilize doped-zirconia nanoparticles in their cubic structure allows the crystallization of powders at temperatures as low as 250 °C. The resulting powders are very fine, with large specific surface areas around 50–150 m² g⁻¹, low agglomeration, and small-sized crystallites around 8–10 nm. After studying the effect of the operating conditions on the stabilization of the cubic crystalline phase, a well-adapted powder was selected and characterized in detail with respect to its microstructure, and its thermal behavior was investigated to eventually prepare an electrode/electrolyte.