Optical, Thermal, and Mechanical Properties of (Y1-xScx)2O3 Transparent Ceramics

Sesquioxides such as Y2O3 and Sc2O3 are important optical materials, but the fabrication of their transparent ceramics remains a challenge due to the ultra-high melting point of over 2400 oC. In this work, a series of (Y1-xScx)2O3 transparent ceramics were successfully fabricated by a simple vacuum sintering process without any sintering additives, and the effect of Scandium (Sc) content on the crystal structure and optical/thermal/mechanical properties were evaluated. Y2O3 and Sc2O3 form a complete solid solution with a cubic bixbyite structure. The formation of (Y1-xScx)2O3 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 mm. In particular, the in-line transmittance in the range of 0.6-6 mm remains above 80% for (Y1-xScx)2O3 with x = 0.23-0.31, while the pristine Y2O3 and Sc2O3 are opaque. Moreover, the mechanical properties including Vickers hardness (Hv), fracture toughness (KIC), and biaxial strength (δb) are evidently enhanced due to the solid solution strengthening, while the thermal conductivity 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 sesquioxides transparent ceramics with high optical and mechanical quality.