A glucose sol-gel combustion method has been developed to synthesize composite nanopowders with equal volume fractions of Y 2 O 3 and MgO. The synthesis involves the generation of precursor foam containing Y 3+ and Mg 2+ cations via the chemical and thermal degradation of glucose molecules in aqueous solutions. Subsequent calcination of the foam gave the composite nanopowders uniform composition and surface areas of 44-62 m 2 /g depending on the relative amount of glucose. Then the nanopowder with an average particle size of 19 nm was consolidated by the hot-pressing technique with different sintering temperatures. The fabricated nanocomposite is midinfrared transparent as the result of fine grains, narrow grain size distribution, and uniform phase domains. The transmittance increases with increase in the sintering temperature and reaches 83.5% at 3-5 lm mid-infrared wave range once the temperature reaches 1350°C, which is close to the theoretical value of 85%. And it is noteworthy that the cutoff wavelength reaches 9.6 lm, which is superior to those of spinel, AlON, and sapphire. And the Vickers hardness of the sample reaches 10.0 AE 0.1 GPa, which is significantly higher than those of the coarse grained single-phase MgO and Y 2 O 3 . The results indicate that the glucose sol-gel combustion and hot-pressing technique is an effective method to fabricate infrared transparent Y 2 O 3 -MgO nanocomposites.

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A sol-gel combustion method has been used to synthesize Y 2 O 3 -50 vol%MgO composite nanopowders. Solutions of the precursor nitrates were mixed with citric acid and ethylene glycol, heated from 200°C to a predetermined temperature gradually, giving nanocrystalline ceramic powders. The influence of the ratio of yttrium nitrate to the whole precursor mixture and the holding temperature on the properties of the composite nanopowder was investigated using a combination of thermal analysis, X-ray diffraction, specific surface area analysis, and scanning electron microscopy techniques. When the ratio of yttrium nitrate to the whole precursor mixture reaches 22.5 mol%, the average particle size of synthesized composite nanopowder is 13 nm and the specific surface area is 45.9 m 2 / g. Then the synthesized Y 2 O 3 -MgO composite nanopowder was consolidated by the hot-pressing technique at 1200°C with different dwell time. As a result, the nanocomposite ceramic prepared with a dwell time of 60 min got the highest transmittance of 75% at 5 lm wavelength. The cut-off wavelength of Y 2 O 3 -MgO nanocomposite ceramic reaches 9.8 lm, which is superior to other mid-IR transparent materials. In addition, the fabricated sample is more or less transparent in visible wavelengths and the transmittance at 0.8 lm is as high as 14.5%.