Improvement on optical and mechanical properties of Y2O3–MgO composites via the enhancement of phase homogeneity

Y2O3–MgO composites are optical materials with promising applications for mid-infrared windows in extreme environments. Considering the refractive index differences between different phases and the Hall–Petch effect, intensifying phase homogeneity and reducing grain size enhances the optical and mechanical properties of composites. The grain sizes of composites are also influenced by phase homogeneity. However, research on the relationship and mechanism of phase homogeneity with the optical and mechanical properties of Y2O3–MgO composites is not quantitative and lacks gradient data support. In this study, the phase homogeneity was quantified and utilized as a gradient parameter to fabricate Y2O3–MgO composites by regulating the solvothermal temperature during powder synthesis. As the phase homogeneity increases, scattering is reduced and the grain size decreases, resulting in improved properties (transmittance at ∼6 μm rises from ∼5.5% to ∼81.5%). The gradientization and quantitative analysis of phase homogeneity in Y2O3–MgO composites can serve as a reference on optical composites, aiding in the optimization of properties.