Sintering and electrical properties of (CeO2)(0.9)(Gd2O3)(0.1) powders prepared by glycine-nitrate process for solid oxide fuel cell applications

Doped CeO2-(CeO2)(0.9)(Gd2O3)(0.1) pellets 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 alpha 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)(0.1) powders with specific surface areas of 19-23 m(2)/g were obtained. Green bodies from the synthesized powders after milling shrunk up to about 1470 degrees C; above which they expanded with heating temperature, whereas those before milling shrank continuously up to a temperature of 1600 degrees C. This difference might milling to about 40% after milling. Therefore the sintered (CeO2)(0.9)(Gd2O3)(0.1) bodies having a theoretical density of 7.25 g/cm(3) were considered to be obtained from the as-milled powders by controlling the sintering time at a sintering temperature higher than 1470 degrees C in air, In the AC impedance measurements, the electrical resistivity of the (CeO2)(0.9)-(Gd2O3)(0.1) bodies, produced from as-milled powders, and sintered at 1500 degrees C with increasing sintering time, showed the minimum total value at the sintering time of 10h. The minimum total resistivity of the (CeO2)(0.9)(Gd2O3)(0.1) bodies sintered at 1500 degrees C for 10 h seems lo be obtained when the sum of the activation energy for the resistivities in the grain and at the grain boundary.