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

Abstract Sesquioxides such as Y₂O₃and Sc₂O₃are 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−xSc_x)₂O₃transparent 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. Y₂O₃and Sc₂O₃form a complete solid solution with a cubic bixbyite structure. The formation of (Y_1−xSc_x)₂O₃solid 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−xSc_x)₂O₃withx= 0.23–0.31, while the pristine Y₂O₃and Sc₂O₃are 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.