| Abstract Scope |
Recent work has demonstrated promise for multicomponent rare earth disilicates (REDS) as environmental barrier coatings (EBC) for SiC-based composites. This involves separating and recombining RE elements, 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. Following a desire to reduce costs, we can look to minerals for inspiration. 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 we present reactivity of REPO4 in 1400°C high-velocity steam for exposures up to 10 days for individual Y,Gd,Dy,Er,Yb phosphates and multicomponent REPO4. Relation between crystallographic properties and steam resistance will be discussed. |