Optical, thermal, and mechanical properties of (Y1−xScx)2O3 transparent ceramics

Abstract Sesquioxides such as Y 2 O 3 and Sc 2 O 3 are important optical materials, but the fabrication of their transparent ceramics remains a challenge due to the ultra-high melting point of over 2400 ° C. In this work, a series of (Y 1− x Sc x ) 2 O 3 transparent ceramics were successfully fabricated by a simple vacuum sintering process without any sintering additives, and the effect of scandium (Sc) content ( x ) on the crystal structure and optical/thermal/mechanical properties was evaluated. Y 2 O 3 and Sc 2 O 3 form a complete solid solution with a cubic bixbyite structure. The formation of (Y 1− x Sc x ) 2 O 3 solid solution promotes the densification of ceramics, leading to the realization of high transparency close to the theoretical transmittance over a wide wavelength range of 0.35–8 µm. In particular, the in-line transmittance in the range of 0.6–6 µm remains above 80% for (Y 1− x Sc x ) 2 O 3 with x = 0.23–0.31, while the pristine Y 2 O 3 and Sc 2 O 3 are opaque. Moreover, the mechanical properties including Vickers hardness ( HV ), fracture toughness ( K IC ), and biaxial flexural strength ( δ b ) are evidently enhanced due to the solid solution strengthening, while the thermal conductivity ( k ) is reduced due to the reduction of photon free path. This study demonstrates that forming of solid solution is a facile and universal approach for preparing sesquioxide transparent ceramics with high optical and mechanical quality.