Tailoring phase domains and properties of transparent Y₂O₃-MgO composites via powder morphology design

While spherical powders are typically favored for enhanced sintering activity, highly transparent Y₂O₃-MgO ceramics have recently been fabricated using rod-like powders. The underlying mechanisms by which powder morphology influences the final microstructure and properties remain unclear. This study reveals that spherical powders yield spherical-phase domains and high mid-wave infrared transmittance (~84% at 3 μm). In contrast, rod-like powders promote elongated phase domains and a higher long-wave infrared transmittance (~82% at 8 μm) with a broader transmission window. Both composites exceed 85% (~6 μm) transmittance (theoretical maximum ~86%). Optical tailoring is attributed to the interplay of Mie scattering, carbon contamination, intrinsic phonon absorption mechanisms, and pinning effect. Composites from rod-like powders also exhibit finer grains and higher hardness (11.3 GPa vs. 10.2 GPa), consistent with the Hall-Petch relationship. This work demonstrates that powder morphology design enables concurrent optimization of performance in transparent materials, offering a general strategy for advanced ceramic engineering.