Study of the Electrophysical Properties of Solid Solutions with a Perovskite Structure in La₂O₃–SrO–Ni(Co,Fe)₂O_3–δ Systems for Cathode Electrodes for Fuel Cells

Abstract—Finely dispersed mesoporous powders of the following composition are synthesized by the method of cocrystallization of nitrate salts with ultrasonic treatment: La_1–xSr_xNiO_3–δ, La_1–xSr_xCoO_3–δ, and La_1–xSr_xFe_0.7Ni_0.3O_3–δ (x = 0.30; 0.40). Based on them, ceramic nanomaterials of the given composition with a coherent scattering region (CSR) of ~65–69 nm (1300°С) are obtained. Ceramics fired at 1300°C are single-phase and have a tetragonal and orthorhombic perovskite-type structure in the La₂O₃‒SrO‒Ni(Co,Fe)₂O_3–δ system. Solid solutions have mixed electron–ion conductivity with transfer numbers t_e = 0.98–0.90 and t_i = 0.02–0.10. Ceramics with a tetragonal perovskite-type crystal structure exhibit higher electrical conductivity than materials having an orthorhombic perovskite-type crystal structure. According to their electrophysical properties related to the structural features of solid solutions, ceramic materials obtained based on them are promising as solid oxide cathodes for average-temperature fuel cells.