Synthesis of Nanosize Ceria by a Combustion Process and Electrical Characterization of HeteroFoaM Porous Ceria Electrodes

Nanosize powders of Sm₂O₃-doped CeO₂ (SDC) containing various dopants (Pr, Rh, Re) were synthesized using respective nitrates and D-gluconic acid (DGA) by a combustion process. The resulting powders were extremely fine (nanosize) and of uniform composition. Porous samples with open porosity were fabricated by sintering. Electrical conductivity was measured by a four probe DC technique over a wide pO₂ range and a temperature range between 200°C and 800°C. The pO₂ was measured using an oxygen sensor. Samples of SDC and SDC with Pr doping exhibited significant electronic conduction in reducing atmospheres above 400°C. Thus, these materials are suitable candidates for SOFC anodes above 400°C. Sintered and powder samples were subjected to various thermal treatments in several atmospheres (oxidizing to reducing) and were characterized by XRD, SEM, and XPS. The purpose of adding the dopants Pr, Rh and Re was to create mixed ionic electronic conductivity in reducing atmospheres at low (<300°C) temperatures. Such materials are potential candidates as SOFC anodes at temperatures possibly lower than 500°C.