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

Abstract

Xerogels and finely dispersed СeO₂–Nd₂O₃ and Gd₂O₃–La₂O₃–SrO–Ni(Co)₂O_3–δ 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°C). The physicochemical characterization of the prepared ceramic materials revealed an open porosity of 7–11% for СeO₂–Nd₂O₃ ceramics and 17–42% for Gd₂O₃–La₂O₃–SrO–Ni(Co)₂O_3–δ ceramics. Cerium oxide-based materials possess a predominantly ionic electrical conductivity with σ_700°С = 0.31 × 10^–2 S/cm (the ion transference number t_i = 0.71–0.89 in the temperature range 300–700°C) due to the formation of mobile oxygen vacancies upon heterovalent substitution of Nd³⁺ for Се⁴⁺. Solid solutions based on gadolinium nickelate and gadolinium cobaltite feature a mixed electronic–ionic conductivity (σ_700°С = 0.59 × 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.