Zirconia electrolytes aging

Raeder, H., Norby T., and Osborn, P.A., Ageing of yttria-stabUized zirconia electrolytes at 1000°C, in Ceramic Processing Science and Technology, Ed. H. Hausner, Columbus, OH, Amer. Ceram. Soc., 1995, 719-723. 

In contrast from the single-phase electrolytes, the two-phase electrolytes are characterized by the deeper aging, and the duration of aging is usually much longer. The absence of equilibrium was reported for the zirconia-based electrolytes held at the temperature of 1100°C for 2000-3000 hours [13], for the Z1O2-SC2O3 electrolyte part of the aging curve has the 5-shape form [34],... 

Scandia doped zirconia (SDZ) is quite attractive as the electrolyte for SOFC s, especially for the intermediate temperature (600-800 °C) SOFC s. The long-term stability was not clarified before Yamamoto et al. reported the aging effect by annealing at higher temperatures [27]. Zr02 with 8 mol %... 

Various authors have reported different temperatures of eutectoid decomposition, ranging from 1000 to 1140 °C [183-185]. The eutectoid transformation is a rather slow process, and is therefore not seen in conventionally aged samples. However, a large cubic phase field also exists which, together vfith slow transformation, facilitates the existence of a fully cubic structure, providing the basis for calcia-stabilized zirconia solid electrolytes. 

K. Kobayashi, H. Kayajima, and T. Masaki [1981] Phase Change and Mechanical Properties of Zirconia-Yttria Solid Electrolyte after Aging, Solid State Ionics 3/4, 489 93. 

Service time. While the volume conductivity of a soUd-state electrolyte such as fully stabihzed (cubic) zirconia (FSZ) reaches a steady state within a comparatively short time, its grain boundary conductivity changes with service time, mostly due to the accumulation of impurities. In PSZ, similar effects occur in relation to the precipitation of tetragonal Zr02 and associated deterioration of conductivity. Because of this aging behavior of PSZ, FSZ is preferred in SOFC applications (Subbarao, 1981 Minh and Takahashi, 1995). 

---