Lu 1/6) 2 Si 2 O 7 has been designed and successfully synthesized following the strategy of high entropy engineering. The asprepared single-phase 6RE-disilicate possesses a new γ-type crystal structure (monoclinic, P2 1 /c) beyond the α-, βand δ-type parent structures of six single RE disilicates. Six-species RE cations are homogeneously distributed on RE lattice sites and our multicomponent disilicate demonstrates outstanding thermal stability from room temperature up to around 1900°C. This work extends the knowledge of strategic multicomponent modification of complex ceramics with extremely high phase stability.

Ti 3 AlC 2 has low density, high elastic modulus, quasi-ductility, and excellent oxidation resistance. However, its relatively low strength needs to be improved. In this study, dense Ti 3 AlC 2 -Y 4 Al 2 O 9 composites (containing 2.5, 5, and 7.5 wt% Y 4 Al 2 O 9 ) were synthesized by hot pressing/solid-liquid reaction using Ti, Al, C, and Y 2 O 3 as initial materials. We investigated the in situ formation process of Y 4 Al 2 O 9 , and studied the change of microstructure and optimization of mechanical properties of the Ti 3 AlC 2 -Y 4 Al 2 O 9 composites. The grain size and aspect ratio of Ti 3 AlC 2 grains are significantly reduced in Ti 3 AlC 2 -Y 4 Al 2 O 9 composites, which is the source of higher strength from room temperature to elevated temperatures. The Ti 3 AlC 2 -5 wt%Y 4 Al 2 O 9 composite shows better optimization in its mechanical properties than other studied composites. In addition, there is an improvement in strength without debit in toughness of the composite.T. Parthasarathy-contributing editor Manuscript No. 30482.

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