Structural and electrical properties of Sr(Ti, Fe)O_3-δ materials for SOFC cathodes

摘要

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, SrTi_0.65Fe_0.35O₃ and SrTi_0.50Fe_0.50O₃ 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 ~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 600°C to 800°C. At 790°C samples show polarization ASR of approximately 0.1 Ω cm2. 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.