Abstract: Magnesium aluminate spinel （MgAl₂O₄） transparent ceramics exhibit superior properties including broad optical transmission range， high mechanical strength， and excellent thermal stability， demonstrating significant application potential in the fields of transparent armor， infrared windows， and fairing. However， the diffusion coefficient of oxygen ions in MgAl₂O₄ is relatively low， and the sintering densification is difficult. Therefore， sintering aid is often introduced during the sintering process. Rare earth sesquioxides， being resistant to volatilization at high temperature， have been shown to effectively promote the densification of MgAl₂O₄ ceramics. This study employed commercially available MgAl?O? powder as the raw material and Y₂O₃ as the sintering aid. The MgAl₂O₄ transparent ceramics were successfully prepared through a combination of pressureless presintering and hot isostatic pressing （HIP）. The microstructure， optical and mechanical properties were systematically characterized and analyzed by scanning electron microscopy （SEM）， UV-Vis-NIR spectrophotometry， and universal testing machine. The results indicate that the MgAl₂O₄ ceramics doped with 0.020%（mass fraction） Y₂O₃ prepared by pressureless presintering at 1 525 ℃ and HIP at 1 600 ℃， the prepared sample exhibits optimal transmittance. The transmittance at 550 and 3 000 nm reaches 84.5% and 87.8%， respectively， while the flexural strength reaches 333.2 MPa. Compared with the undoped Y₂O₃ samples， the average grain size of the MgAl₂O₄ ceramics doped with 0.020% Y₂O₃ decrease from 8 μm to 4 μm， and the flexural strength is increase by 9.79%.

Key words: magnesium aluminate spinel; transparent ceramics; Y₂O₃; sintering aid; transmittance; flexural strength