Multi-component 20La 2 O 3-20TiO 2-20Nb 2 O 5-20(Al 2 O 3 /ZrO 2 )-20(ZrO 2 / Ta 2 O 5 ) glasses with ultra-high refractive index and mechanical properties inspired by high-entropy design

The highly refractive glasses with excellent mechanical properties (hardness, Young's modulus, and fracture toughness) are highly desired for the lenses used in small optical devices. In this study, a series of five-primarycomponent 20La 2 O 3 -20TiO 2 -20Nb 2 O 5 -20(Al 2 O 3 /ZrO 2 )-20(ZrO 2 /Ta 2 O 5 ) (LTNAZ, LTNAT, LTNZT) glasses were designed by using high-entropy strategy and successfully elaborated through a containerless meltingsolidification process. The highest refractive index ( n d ) of the glasses reach up to 2.25. The maximum vickers hardness ( H V ), Young's modulus ( E ), and indentation fracture toughness ( K IFT ) are 10.74 GPa, 157.5 GPa, and 1.23 MPa m 0.5 respectively. The glasses exhibit good glass forming ability with kinetic window ( Delta T ) ranging from 80 to 116 degrees C. The excellent comprehensive performances of the glasses are attributed to the high electronic polarizability and dissociation energy, as well as the synergistic effect of multiple components in the highentropy effect. The glasses will be promising host materials for optical applications such as digital product lenses, endoscopes and mini size lasers.