Reactivity in LaGaO₃/Ni and CeO₂/Ni systems

The reactivity in CeO₂/Ni and LaGaO₃/Ni systems, which are constituents of intermediate temperature solid oxide fuel cell (IT-SOFC) anodes, has been investigated both computationally and experimentally. The CALPHAD-method (CAL-culating of PHAse Diagrams), employing BINGSS and THERMOCALC software, was used to obtain a self-consistent set of Gibbs energy functions describing the systems. Interactions in the LaGaO₃/Ni system were predicted using a thermodynamic database developed for the La-Ga-Ni-O system. Similarly, to analyze the CeO₂/Ni system, the Ce-Ni-O ternary phase diagram was calculated using known thermodynamic data for binary Ce-O, Ni-O, and Ce-Ni systems. The experimental work was designed based on the calculated phase diagrams. While the La-Ga-Ni-O system experiments were conducted in air, the Ce-Ni-O system was also investigated in a reducing atmosphere. The calculated Ce-Ni-O diagram is in good agreement with the experimental results. It has been found that NiO does not react with CeO ₂. Extended solid solutions of La(Ga,Ni)O₃, La ₂(Ni,Ga)O₄, and La₄(Ni,Ga)₃O ₁₀ were found in the La-Ga-Ni-O system. Additionally, the compound LaNiG₁₁O₁₉, with magnetoplumbite-type structure, has been found, which has not been reported in the literature so far. It is concluded that La₂NiO₄ is not chemically compatible, as a cathode material, with the LSGM electrolyte.