Thermal stability and field assisted sintering of cerium-doped YSZ ceramic nanoparticles obtained via a hydrothermal process

Owing to its extraordinary range of properties, yttria-doped zirconia holds a unique place among the ceramic oxide systems. To improve the properties for some specific custom design applications, co-doping with other rare earth oxides such as ceria is needed. The aim of this paper is to identify the correlations between the phase composition evolution with increasing thermal treatment temperature in order to establish the thermal stability in connection with the ceria content and how does it influence the yttria-stabilised zirconia microstructure. The ZrO2–3Y2O3–nCeO2 (n = 3, 6 and 9 wt.%) samples were obtained by a hydrothermal process and submitted to a thermal treatment up to 1600 °C. Intensive characterization was performed via X-ray powder diffraction and EDX analysis. It was found that up to 400 °C, a monophasic structure was formed. At higher temperatures tetragonal zirconia is formed as a major phase with the presence of secondary monoclinic and cubic phases, depending on the Ce content and thermal treatment temperature. Sintered compacts with densities up to 99.5% from the theoretical density were obtained starting from the 6%CeO2–3%Y2O3–ZrO2-nanostructured powders using a special field-assisted (FAST) sintering process. With increasing CeO2 content to 9% only, tetragonal zirconia with 6–9 nm crystallite sizes is formed during the FAST sintering process