| Abstract Scope |
Xenotime minerals are rare earth (RE) phosphates of the type REPO4 where RE is found to be primarily Y, with minor amounts of Gd, Dy, Er, Yb. Prior work demonstrated that YbPO4 had necessary properties for an environmental barrier coating (EBC) however desired reductions in EBC thermal conductivity can be achieved with mixed REPO4. Multicomponent rare earth compositions are synthesized via combining single component rare earth compounds. However, rare earth separation into single components is costly, slow, and generates significant waste. Thus, motivation exists to use multicomponent rare earth minerals such as xenotime directly without separation and recombination of RE. In this work, properties of naturally occurring xenotime minerals, individual REPO4 (RE=Y,Gd,Dy,Er,Yb), synthetic xenotime, and equimolar (Y,Gd,Dy,Er,Yb)PO4 are explored to evaluate EBC properties. Phase purity, thermal expansion, thermal conductivity, high temperature steam resistance, and CMAS resistance were evaluated. Efficacy of the proposed xenotime mineral as thermal barrier (T)EBCs is demonstrated. |