Long‐term oxidation and electrical behavior of Nb‐doped Ti3SiC2 as solid oxide fuel cell interconnects
Nb‐doped Ti3SiC2 compounds ((Ti1‐ xNbx)3SiC2, x=0%, 2%, 5%, 7%, and 10%) as novel interconnect materials of intermediate temperature solid oxide fuel cell (IT‐SOFC) were studied in the simulated cathode atmosphere. The long‐term oxidation behaviors and area‐specific resistance (ASR) of these compounds have been investigated at 800°C up to 700 hours. Among these compounds, (Ti0.95Nb0.05)3SiC2 shows the best oxidation resistance and lowest postoxidation ASR (5.6 mΩ·cm2 after exposure at 800°C in air for 700 hours), endowing it a great promising material in the application as interconnect of IT‐SOFC. After oxidation, Nb is mainly doped uniformly into the lattice of rutile‐TiO2 (r‐TiO2) grains formed on the tested compounds. Nb doping could decrease the concentrations of both oxygen vacancies and titanium interstitials in r‐TiO2. As a result, the oxidation rate of (Ti,Nb)3SiC2 decreases remarkably, the structure of the oxide scale changes from a duplex layer of TiO2 outer layer and TiO2+SiO2 mixture inner layer to a single mixture layer. Nb doping also increases the amount of semifree electrons, causing the significant reduce of the postoxidation ASR of (Ti,Nb)3SiC2.
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