Synthesis and characterization of Ce_0.99-xGd_xCu_0.01O_2-δ solid solutions

Full text: Doped ceria solid solutions have been regarded promising electrolyte materials for intermediate and low temperature solid oxide fuel cells (SOFCs) since their ionic conductivities are higher than that of the traditional yttrium-stabilized zirconia (YSZ) electrolyte. However, one of the main drawbacks of ceria based electrolytes are the high sintering temperatures (1350-1600 °C) required to full densification. In order to improve the sinterability of doped ceria ceramics, one processing alternative is adding transition metal oxides with low melting-point, such as CuO, into commercial or synthesized powders. In this scenario, this work is focused on evaluate the effect of Gd doping varying from 0 to 30 mol% on structure, sintering behavior, microstructure and electrical properties of Cu-doped ceria solid solutions. Powders with nominal compositions Ce_0.99-xGd_xCu_0.01 O_2-δ (x = 0, 0.1, 0.2, and 0.3) were synthesized by the polymeric precursor method. As-prepared and calcined (500 °C for 1 h) powders were characterized by thermogravimetry, X-ray diffractometry combined with Rietveld refinement and dilatometry from room temperature to 1200 °C. Relative density and microstructural inspection were performed on pellets sintered from 950 to 1050 °C. From the XRD patterns, well-crystalline cubic fluorite structured solid solutions were successfully synthesized by the herein used chemical route. Crystallite size decreased with increase in gadolinium doping in ceria lattice. A significant reduction of about 400 °C in densification sintering temperature was obtained when compared with conventional Cu-free CGO (gadolinium doped ceria) ceramics from literature. Reference: [1] Choubhury, A; Chambra, H; Arora, A. Renewable and sustainable emervw reviews, v. 20, P. 430-442, 2013. (author)