IRG1-4

2022 IRG-1: A New Type of Compositionally Complex M₅Si₃ Silicides: Cation Ordering and Unexpected Phase Stability

A new type of compositionally complex M₅Si₃silicides is reported. Notably, (V_1/5Cr_1/5Nb_1/5Ta_1/5W_1/5)₅Si₃ forms the hexagonal γ (D8₈) phase, while all its five constituent binary silicides, V₅Si₃, Cr₅Si₃, Nb₅Si₃, Ta₅Si₃, and W₅Si₃, are stable in the tetragonal α (D8_l) or β (D8_m) phases. Rietveld refinements of X-ray diffraction patterns and aberration-corrected scanning transmission electron microscopy reveal cation ordering, which reduces the configurational entropy. This work expands the field of high-entropy and compositional complex ceramics by not only discovering a new compositionally complex silicide phase but also demonstrating cation ordering and unusual phase stability. These compositionally complex silicides can be combined with refractory high-entropy alloys to make the high-entropy counterparts to the Nb-silicide and Mo-Si-B composites.

S. Shivakumar, M. Qin, D. Zhang, C. Hu, Q. Yan, J. Luo, Scripta Materialia, 212, 114557 (2022) https://doi.org/10.1016/j.scriptamat.2022.114557

Jian Luo (University of California, San Diego)