Manufacturing of NiO/NiTiO3 porous substrates and the role of zirconia impurities during sintering

Anode substrates based on Ni/TiO2 cermets were fabricated for planar solid oxide fuel cells (SOFC) with the aim of improving the thermoelastic behavior of Ni/8 mol.% Y2O3-stabilized zirconia (8YSZ) substrates. This offers the possibility of adjusting the thermal expansion coefficient to any electrolyte membrane considered. NiO/NiTiO3 specimens were fabricated from Coat-Mix® powders by rate-controlled and constant heating rate sintering. The heat treatments led to a significant change in activation energy and, especially at high sintering temperatures, in the morphology of the microstructures compared with NiO/8YSZ substrates. A TEM investigation revealed droplet-shaped impurities at the grain boundaries, which are regarded as the reason for liquid phase sintering of these substrates.