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

Finely dispersed СeO₂–Nd₂O₃ and Gd₂O₃–La₂O₃–SrO–Ni(Co)₂O_3–δ mesoporous powders are synthesized by co-crystallization of the corresponding nitrates solutions with ultrasonic treatment and used to prepare nanoceramic materials with a fluorite-like, orthorhombic perovskite and tetragonal perovskite crystal structures respectively with CSR ~ 55–90 нм (1300ºC). The study of physicochemical properties of the obtained ceramic materials revealed an open porosity 7–11% for СeO₂–Nd₂O₃ and 17–42% for Gd₂O₃–La₂O₃–SrO–Ni(Co)₂O_3–ä. Cerium oxide-based materials possess a predominantly ionic electrical conductivity with σ_700ºС = 0.31 · 10^–2 S/cm (ion transfer number t_i = 0.71–0.89 in the temperature range 300–700°C) due to the formation of mobile oxygen vacancies at heterovalent substitution of Nd³⁺ for Се⁴⁺. Solid solutions based on lanthanum nickelate and cobaltite feature a mixed electronic-ionic conductivity with σ_700°С = 0.59 ∙ 10^–1 S/cm with the electron and ion transfer numbers t_e = 0.92–0.99 and t_i = 0.08–0.01. The obtained ceramic materials are shown to be promising as solid oxide electrolyrtes and electrodes for medium temperature fuel cells.