Investigation on the properties of Ta doped Ti3SiC2 as solid oxide fuel cell interconnects

The oxidation behaviours and electrical properties of 5 at% Ta doped Ti3SiC2 solid solution have been investigated at 800 °C in air for up to 500 h. The oxidation kinetics of (Ti0.95Ta0.05)3SiC2 follows a parabolic law. The oxidation rate constant is 7.33 × 10−14 g2 cm−4 s−1, which is lower than those of Ti3SiC2, (Ti0.95Nb0.05)3SiC2 and Crofer 22 APU. Ta doped r-TiO2 formed (Ti0.95Ta0.05)3SiC2 during the oxidation process. Ta doping can limit the outward diffusion of Ti by decreasing the native Ti interstitials concentration and simultaneously restraining the inward diffusion of oxygen by decreasing the O vacancy concentration. As a result, the oxidation resistance is significantly improved and the oxide scale structure of Ti3SiC2 changes from a double-layer to a monolithic layer. The ASR of (Ti0.95Ta0.05)3SiC2 after oxidation at 800 °C in air for 500 h is 29.5 mΩ cm2, which is much lower than that of Ti3SiC2. Ta doping can increase the electron concentration in r-TiO2 and thereby increase the electrical conductivity of r-TiO2. Therefore, the ASR of (Ti0.95Ta0.05)3SiC2 after oxidation is lower compared to that of Ti3SiC2.