Tantalum Oxide Coatings as Candidate Environmental Barriers

Tantalum (Ta) oxide, due to its high-temperature capabilities and thermal expansion coefficient similar to silicon nitride, is a promising candidate for environmental barriers for silicon (Si) nitride-based ceramics. This paper focuses on the development of plasma-sprayed Ta oxide as an environmental barrier coating for silicon nitride. Using a D-optimal design of experiments, plasma-spray processing variables were optimized to maximize coating density. The effect of processing variables on coating thickness was also determined. X-ray diffraction (XRD) was use to ascertain that the as-sprayed coatings were comprised of and -Ta2O5, but were fully converted to -Ta2O5 after a 1200 °C heat treatment. Grain growth of the Ta2O5 followed a time dependence of t at 1200 °C.