Structural and electrical properties of Sr(Ti, Fe)O3-δ materials for SOFC cathodes

Doped strontium titanates are very versatile materials. Iron doped SrTiO3 can be used, for example, as a material for resistive gas sensors and fuel cell electrodes. In this paper, two compositions based on Fe doped SrTiO3 were studied as possible candidates for cathode application in SOFCs. Namely, SrTi0.65Fe0.35O3 and SrTi0.50Fe0.50O3 were examined. A chemical reactivity between electrode and YSZ electrolyte material was investigated, since Sr containing cathode materials in contact with YSZ electrolyte are prone to form insulating phases. Electrical conductivity of bulk samples showed relatively low total conductivities of 0.4 S cm(-1) and similar to 2 S cm(-1) for STF35 and STF50 respectively. Suitability for cathode application was studied by Electrochemical Impedance Spectroscopy in a symmetrical electrode configuration. Area specific resistance (ASR) was determined in the temperature range from 600A degrees C to 800A degrees C. At 790A degrees C samples show polarization ASR of approximately 0.1 abroken vertical bar A cm(2). It can be expected that further reduction of electrode ASR can be obtained by introduction of ceria barrier layer and tailoring of the electrode microstructure.