Fabrication and characterization of oriented Nd2NiO4 bulk and cathode for low-temperature operating solid oxide fuel cell

Textured Nd2NiO4 (NNO) bulks were fabricated by slip casting in a 5 T magnetic field generated by a superconducting magnet. The easy-magnetization axis of NNO was determined by X-ray diffraction (XRD) measurements performed on the surfaces parallel and perpendicular to the applied magnetic field direction of the sintered bulk NNO ceramics. The anisotropic electric conductivity and thermal expansion coefficient of the textured NNO were characterized by the conventional DC four-terminal method and dilatometry, respectively. A higher electric conductivity and lower thermal expansion in the direction perpendicular to the c-axis were confirmed. Based on the obtained experimental data, fabrication of the a-b plane perpendicular-oriented NNO cathode layer on a Gd-doped ceria (GDC) electrolyte was finally attempted in a 0.9 T magnetic field generated by neodymium magnets. The effect of the rotation of the magnetic field in the horizontal plane on the orientation condition of the NNO layer was also investigated. The rotation of the magnetic field could produce the random orientation of the c-axis while retaining the a-b plane orientation against the electrolyte. Based on the performance tests of single cells equipped with different oriented NNO cathodes, the ideal situation of the NNO cathode layer leading to good performance is proposed.