Abstract Scope |
Recent work has demonstrated promise for multicomponent rare earth disilicates (REDS) as environmental barrier coatings (EBC) for SiC-based composites. Synthesis of REDS requires separating RE from ores and recombining them for EBCs, creating a cost-prohibitive concept. Additionally, high-temperature steam exposure of REDS results in the formation of RE monosilicates leading to shorter lifespan due to cracking on cooling. RE-containing minerals offer opportunities for EBC use without costly separation of RE elements. Xenotime-based RE phosphates (REPO4), RE = (Y,Gd,Dy,Er,Yb), are a promising material class due to demonstrated improvements to several EBC requirements compared to REDS and being a commonly mined source of RE elements. Preliminary study of REPO4 indicates a reduction in parabolic rate of steam reaction through the production of highly stable RE2O3. Here results for reactivity of REPO4 in 1400°C high-velocity steam exposures for times up to 10 days are reported for individual Y,Nd,Gd,Dy,Er,Yb phosphates and multicomponent REPO4. |