在高超音速飞行下，飞行器的中波红外窗口面临着气动加热导致的高温透过率下降和高温辐射增强的挑战，在高马赫应用中，选择窗口材料时必须对材料的高温透过率与高温热辐射这两个性能进行考察。本文采用傅里叶红外光谱仪测试了蓝宝石单晶、钇铝石榴石单晶、镁铝尖晶石陶瓷、氟化镁陶瓷和氧化钇陶瓷5 种常见中波红外窗口材料在50 ℃～400 ℃的高温透过性能和高温辐射性能。考察了这几种窗口材料的高温透过率下降趋势和高温辐射增强。结果表明，相对于其他3 种材料，氟化镁和氧化钇材料在3～5 μm 应用波段的高温透过率下降很小，同样高温辐射也较小。此外，氧化钇表现出非常优异的超低红外辐射性能，是一种非常有应用前景的中波红外窗口材料。

The transmittance and radiance of mid-infrared window materials at elevated temperature require investigation. Due to their reduced transmittance and higher radiance, these materials are applied to hypersonic aircraft windows where aerodynamic heating is a large challenge. Five types of mid-infrared widow materials are widely used and selected for this study: sapphire, YAG, spinel, MgF₂, and Y₂O₃. Their transmittance reduction and radiance increase in the temperature range from 50 ℃ to 400 ℃ were studied by an FTIR spectrometer. The results show that MgF₂and Y₂O₃exhibit better properties at high temperature and far less reduction in transmittance and the increase in radiance was observed in the range of 3-5 μm compared with other three kinds of materials. Particularly, Y₂O₃has an extremely low radiance and thus is a very promising mid-infrared window material.