Synthesis and Research of Electrolyte and Electrode Materials in CeO2–Nd2O3 and Gd2O3–La2O3–SrO–Ni(Co)2O3 – δ Systems for Medium-Temperature Fuel Cells

Abstract

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.