Phase formation capability and compositional design of β-phase multiple rare-earth principal component disilicates

A key strategy to design environmental barrier coatings focuses on doping multiple rare-earth principal components into β-type rare-earth disilicates (RE(2)Si(2)O(7)) to achieve versatile property optimization. However, controlling the phase formation capability of (nRE(xi))(2)Si(2)O(7) remains a crucial challenge, due to the complex polymorphic phase competitions and evolutions led by different RE(3+) combination. Herein, by fabricating twenty-one model (RE(I)(0.25)RE(II)(0.25)RE(III)(0.25)RE(IV)(0.25))(2)Si(2)O(7) compounds, we find that their formation capability can be evaluated by the ability to accommodate configurational randomness of multiple RE(3+) cations in β-type lattice while preventing the β-to-γ polymorphic transformation. The phase formation and stabilization are controlled by the average RE(3+) radius and the deviations of different RE(3+) combinations. Subsequently, based on high-throughput density-functional-theory calculations, we propose that the configurational entropy of mixing is a reliable descriptor to predict the phase formation of β-type (nRE(xi))(2)Si(2)O(7). The results may accelerate the design of (nRE(xi))(2)Si(2)O(7) materials with tailored compositions and controlled polymorphic phases.