Synthesis and Physicochemical Characterization of Solid Oxide Electrolyte and Electrode Materials for Medium-Temperature Fuel Cells

Xerogels and finely dispersed CeO2-Nd2O3 and Gd2O3-La2O3-SrO-Ni(Co)(2)O3-delta mesoporous powders are synthesized by cocrystallization of the corresponding nitrate solutions with ultrasonic treatment, and used to prepare nanoceramic materials with a fluorite-like and orthorhombic perovskite crystal structures, respectively, with CSRs of ca. 55-90 nm (1300 degrees C). The physicochemical characterization of the prepared ceramic materials revealed an open porosity of 7-11% for CeO2-Nd2O3 ceramics and 17-42% for Gd2O3-La2O3-SrO-Ni(Co)(2)O3-delta ceramics. Cerium oxide-based materials possess a predominantly ionic electrical conductivity with sigma(700 degrees C) = 0.31 x 10(-2) S/cm (the ion transference number t(i) = 0.71-0.89 in the temperature range 300-700 degrees C) due to the formation of mobile oxygen vacancies upon heterovalent substitution of Nd3+ for Ce4+. Solid solutions based on gadolinium nickelate and gadolinium cobaltite feature a mixed electronic-ionic conductivity (sigma(700 degrees C) = 0.59 x 10(-1) S/cm) with the electron and ion transference numbers t(e) = 0.92-0.99 and t(i) = 0.08-0.01. The prepared ceramic materials are shown to be promising as solid oxide electrolytes and electrodes for medium-temperature fuel cells.