Electrical resistivity of low temperature sintered perovskites

Lanthanum–Manganese perovskites are suitable for application as a cathode contact layer in SOFC-stacks. This work describes the resistivity of Lanthanum–Manganese samples which were pre-sintered at different temperatures before annealing at 850 °C in air. Due to the different degrees of sintering, measured resistivity values of low temperature sintered perovskites are higher than resistivity values reported in the literature. For a low resistive and long-term stable contact between cathode and interconnector in SOFC stacks, it is necessary to search for an optimal contact layer made of paste. The main factors affecting the properties of the contact layer are the chemical composition, the grain size distribution of the powder and the organic content of the paste. The results of this work show that with several Lanthanum–Manganese perovskites low resistivity with low sintering temperature can be realized. A bimodal grain size distribution is favorable for a low ageing rate. The fine fraction is responsible for generating the conduction paths and the coarse fraction prevents the volume shrinkage. The paste for the contact layer should have an optimal content of organic. Empirical models are not sufficient to estimate the resistivity of the low temperature sintered perovskites from known bulk resistivity and porosity.