Sintering and Electrical Properties of (CeO2)0.9(Gd2O3)0.1Powders Prepared by Glycine-Nitrate Process for Solid Oxide Fuel Cell Applications

Doped CeO2-(CeO2)0.9(Gd2O3)0.1pellets were prepared using the glycine-nitrate process with various sintering times and sintering temperatures. Compositional and structural characterizations were carried out using X-ray diffraction (XRD) with CuK? radiation, a scanning electron microscope (SEM) and a Transmission electron microscope (TEM). Sintering and electrical characteristics were investigated using dilatometer measurement and the AC impedance analyser. Powder characteristics were also investigated by the BET method. Polycrystalline (CeO2)0.9(Gd2O3)0.1powders with specific surface areas of 19-23 m2/ g were obtained. Green bodies from the synthesized powders after milling shrunk up to about 1470° C, above which they expanded with heating temperature, whereas those before milling shrank continuously up to a temperature of 1600° C. This difference might be attributed to the change of the packing density of the synthesized powders upon milling: from 25% without milling to about 40% after milling. Therefore the sintered (CeO2)0.9(Gd2O3)0.1bodies having a theoretical density of 7.25 g/cm3were considered to be obtained from the as-milled powders by controlling the sintering time at a sintering temperature higher than 1470° C in air. In the AC impedance measurements, the electrical resistivity of the (CeO2)0.9-(Gd2O3)0.1bodies, produced from as-milled powders, and sintered at 1500° C with increasing sintering time, showed the minimum total value at the sintering time of 10 h. The minimum total resistivity of the (CeO2)0.9(Gd2O3)0.1bodies sintered at 1500° C for 10 h seems to be obtained when the sum of the activation energy for the resistivities in the grain and at the grain boundary.