Contact Resistance of Ceramic Interfaces Between Materials Used for Solid Oxide Fuel Cell Applications

The contact resistance can be divided into two main contributions. The small area of contact between ceramic components results in resistance due to current constriction. Resistive phases or potential barriers at the interface result in an interface contribution to the contact resistance, which may be smaller or larger than the constriction resistance.

The contact resistance between pairs of three different materials were analysed (stron-tium doped lanthanum manganite, yttria stabilised zirconia and strontium and nickel doped lanthanum cobaltite), and the effects of temperature, atmosphere, polarisation and mechanical load on the contact resistance were investigated.

The investigations revealed that the mechanical load of a ceramic contact has a high influence on the contact resistance, and generally power law dependence between the contact resistance and the mechanical load was found. The influence of the mechanical load on the contact resistance was ascribed to an area effect.

The contact resistance of the investigated materials was dominated by current constric-tion at high temperatures. The measured contact resistance was comparable to the resis-tance calculated on basis of the contact areas found by optical and electron microscopy. At low temperatures, the interface contribution to the contact resistance was dominating. The cobaltite interface could be described by one potential barrier at the contact interface, whereas the manganite interfaces required several consecutive potential barriers to model the observed behaviour. The current-voltage behaviour of the YSZ contact interfaces was only weakly non-linear, and could be described by 22 ± 1 barriers in series.

Contact interfaces with sinterable contact layers were also investigated, and the mea-sured contact resistance for these interfaces were more than 10 times less than for the other interfaces.