Phase stability, microstructure and high-temperature properties of NbSi2- and TaSi2-oxide conducting ceramic composites
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NbSi2- and TaSi2-based electroconductive ceramic composites with the addition of 40–70 vol% Al2O3 and ZrO2 particles were fabricated by high-temperature sintering (1400–1600 °C) under argon. Their phase stability, microstructural evolution, oxidation kinetics and electrical properties were studied at high temperatures. The densification of the composites was improved by increasing the oxide phase content and sintering temperature. The interaction of the starting metal disilicides with residual oxygen sources resulted in the formation of the hexagonal-structured 5–3 metal silicide (Nb5Si3 and Ta5Si3) phases. The increasing sintering temperature and volume percentage of the oxide phase reduced the pest oxidation, particularly for the silicide–alumina composites, which exhibited lower oxidation-induced mass changes than their dense monolithic metal silicides. Depending on the silicide–oxide volume percentage, their electrical conductivities ranged from 5.3 to 111.3 S/cm at 900 °C. Their phase stability, reduced oxidation rates and high electrical conductivities at high temperatures show promise for future high-temperature applications in advanced sensing.
This research was funded by the U.S. Department of Energy, National Energy Technology Laboratory under contract DE-FE0012383. The authors greatly appreciate Dr. Maria Reidpath from the U.S. Department of Energy for her insight and valuable guidance. We also acknowledge the use of the WVU Shared Research Facilities.
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Conflict of interest
No conflicts of interest.
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