Synthesis and Research of Electrolyte and Electrode Materials in CeO₂–Nd₂O₃ and Gd₂O₃–La₂O₃–SrO–Ni(Co)₂O_3 – δ Systems for Medium-Temperature Fuel Cells

Using the method of the joint crystallization of solutions of nitrate salts with ultrasonic treatment, xerogels and highly dispersed mesoporous powders of the following composition are synthesized: (CeO₂)_1 – x(Nd₂O₃)_x (x = 0.02; 0.05; 0.10), Gd_1 – xSr_xCo_0.5O_3 – δ (x = 0.1, 0.15, 0.2, 0, 25), Gd_0.4Sr_0.1Ni_0.5O_3 – δ, and Gd_0.125La_0.125Sr_0.25Co_0.5O_3 – δ; and based on them, nanoceramic materials with a crystalline cubic structure of the fluorite type, as well as an orthorhombic and tetragonal structure of the perovskite type with CSR ~ 55–90 nm (1300°С), respectively, are obtained. The physicochemical properties of the resulting ceramics are studied; it is revealed that it has an open porosity of 7–11% for the composition (CeO₂)_1 – x(Nd₂O₃)_x and 17–42% for materials with the Gd_1 – xSr_xCo_0.5O_3 – δ, Gd_0.4Sr_0.1Ni_0.5O_3 – δ, and Gd_0.125La_0.125Sr_0.25Co_0.5O_3 – δ composition. Materials based on cerium oxide predominantly have the ionic (ion transport numbers t_i = 0.71–0.89 in the range 300–700°С) type of electrical conductivity due to the formation of mobile oxygen vacancies in the heterovalent substitution of Ce⁴⁺ by Nd³⁺; and σ_700°С = 0.31 × 10^–2 S/cm Solid solutions based on nickelate and lanthanum cobaltite have mixed electron-ionic conductivity, σ_700°С = 0.59 × 10^–1 S/cm with transfer numbers t_e = 0.92–0.99 and t_i = 0.08–0.01. The prospects for using the obtained ceramic materials as solid oxide electrolytes and electrodes for medium-temperature fuel cells (FCs) are shown.