Features of electrical conductivity of complex Cu-Mn-ceria-based electrolytes

Fuel cells are the most efficient means to directly convert stored chemical energy to usable electrical energy (an electrochemical reaction). Doped ceria is considered to be a promising electrolyte for operation at intermediate temperatures (500 – 600°C). It has been reported that a reduction of ceria can be neglected at this temperature. However, such temperatures are not suitable for singly doped ceria as an electrolyte in a SOFC or other devices due to high electrical resistance. Structural modification of ceria-based solid solutions by co-doping is one of the possible ways to improve their electrical conductivity at this temperature range. In this work, tri-doped ceria based solid electrolyte materials for intermediate temperature solid oxide fuel cell were synthesized by the co-precipitation method with sonication. The materials were characterized via thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, Wagner’s polarization technique, and electrochemical impedance spectroscopy. The powders were isostatically pressed at 150 MPa and sintered at 1000°C for 4 h in air to form electrolyte discs for testing. The relative densities of all the samples were more than 90 % after sintering at 1000°C. The electrical conductivity of these materials was measured by an impedance spectroscopy in the temperature range of 500 – 750°C in air. The conductivity increased with the increasing oxygen vacancies that were induced by charge compensation. It was shown that the Cu0.08Mn0.02Nd0.05Ce0.85O2 ceramics can become a promising electrolyte.

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