E.Yu. Pikalova

Structural and Electrical Properties of Composites Based on Ni and NiAl Alloys for SOFC Application

Ni and NiAl alloys were utilized as the components of the composites on the base of Zr0.81Y0.19O2-δ and Al2O3 ceramic powders. The synthesis of composites was performed directly from the mechanical mixtures of metal and ceramic powders by the air plasma spraying method. The samples were made in the shape of porous tubes 20 cm long by 1 cm in diameter. Phase content and their weight ratio were evaluated by the XRD method after spraying and heat treatment at 1350 °C in different atmospheres. It was found that in the deposited samples, Ni stays mainly in a metal state with a small amount of NiO which at the stage of Ar treatment completely transforms into metal Ni. Doping by Al in a small amount (5%) leads to an appearance of spinel which, after decomposition and reduction in hydrogen, favours more uniform Ni distribution in the ceramic matrix and prevents a coarsening of Ni particles. This leads to the cermet having increased conductivity and better thermal properties. The total conductivity of Ni95Al5-Al2O3 cermet in hydrogen was 1374 S/cm at 600 °C with the mean value of the coefficient of thermal expansion equal to 10.5 × 10−6 K−1 in the range of 25–900°С which makes it a prospect for usage as a supported anode for solid oxide fuel cell production.

Development of the Cathode Materials for Intermediate-Temperature SOFCs Based on Proton-Conducting Electrolytes

High-temperature proton-conducting oxide materials are of great fundamental interest due to the phenomenon of proton conductivity which appears with oxygen-ionic conductivity in a humidified atmosphere and is strongly dependent on temperature. The practical interest associated with the use of such Co-ionic electrolyte materials in solid oxide fuel cells (SOFCs) derives from the increased efficiency as a result of the higher open circuit voltage and, correspondingly, power output characteristics in comparison with those of SOFCs based on unipolar oxygen-ion conducting electrolytes. Today there is much work directed toward enhancing an SOFC’s electrochemical characteristics by developing new cathode materials that have excellent electrocatalytic activity. Thermal affinity between electrolyte and cathode materials should also be considered in order to attain both long-term stability and cycling. In this work the analysis of structural, electrical, and thermal properties of simple and layered cobaltites (GdBaCo2O5 + δ, NdBaCo2O5 + δ, Ba0.5Sr0.5CoO3–δ, Y0.8Ca0.2BaCo4O7 + δ), cobaltite-ferrites (NdBa0.5Sr0.5Co1.5Fe0.5O5 + δ, GdBaCoFeO5 + δ, Ba0.5Sr0.5Co0.8Fe0.2O3–δ, Ba0.5Sr0.5Co0.2Fe0.8O3–δ, La0.6Sr0.4Co0.2Fe0.8O3), nikelites (La2NiO4 + δ and its alkali earth element substituted derivatives) and nikelate (LaNi0.6Fe0.4O3–δ) was investigated in terms of their perspective applications in intermediate-temperature SOFCs based on proton-conducting electrolytes.