High-entropy R 2 O 3 -Y 2 O 3 -TiO 2 -ZrO 2 -Al 2 O 3 glasses with ultrahigh hardness, Young's modulus, and indentation fracture toughness.

Glasses with high hardness, high Young's modulus, and high fracture toughness become crucial materials which are urgently needed in the protective covers for various electronic displays. Here, a paradigm is presented that the conceptual design of high-entropy materials is adaptable to high performance oxide glasses. We designed the multi-component glass compositions of 18.77RO-4.83YO-28.22TiO-8.75ZrO-39.43AlO (R = La, Sm, Gd) and elaborated successfully the glassy samples through a containerless solidification process. The as-prepared samples demonstrated the outstanding mechanical and optical properties. The measured hardness, Young's modulus, and indentation fracture toughness of the high-entropy (R = Gd) glass are 12.58 GPa, 177.9 GPa, and 1.52 MPa·m, respectively, in which the hardness and Young's modulus exhibit the highest value among the reported oxide glasses. Structural analysis revealed that the excellent mechanical properties are attributed to the large dissociation energies and the high field strength of AlO, TiO, and ZrO and the complex interaction between atoms caused by high entropy.