Study of the Physicochemical Properties of Nanopowders and Ceramics Based on the CeO2–Rare Earth Oxides (Sm2O3, Nd2O3, Dy2O3) Systems as Electrolyte Materials for Medium-Temperature Fuel Cells

Abstract

Highly dispersed powders based on the CeO₂–rare earth oxides (Sm₂O₃, Nd₂O₃, Dy₂O₃) systems were synthesized using the method of cocrystallization of nitrate salts. On their basis, ceramic materials were obtained, which are solid solutions with a cubic lattice of the fluorite type with coherent scattering regions (CSRs) of ~ 66–88 nm (1300°С) and open porosity in the range of 2.0–6.5%. A comparative study of the physical and chemical properties of the obtained ceramics showed that in the systems CeO₂–Nd₂O₃ and CeO₂–Dy₂O₃ the dense and low-porosity materials are formed only by introducing a sintering additive in the form of zinc oxide. The resulting ceramics have a mixed type of conductivity, but in the medium-temperature range the ionic mechanism of electrical conductivity predominates (ion transport numbers t_i = 0.75–0.91 in the range of 300–700°С). The CeO₂ samples containing 20 mol % Sm₂O₃ and 15 mol % Nd₂O₃ or Dy₂O₃ have the highest ionic conductivity in the temperature range of 500–700°С: σ_700°С = 1.3 × 10^–2 S/cm, σ_700°С = 0.46 × 10^–2 S/cm, and σ_700°С = 0.43 × 10^–2 S/cm, respectively. Based on their physicochemical properties (density, open porosity, type and mechanism of specific electrical conductivity), the obtained ceramic materials are promising as solid oxide electrolytes for medium-temperature fuel cells.