Synthesis and processing of nanocrystalline powders for IR transparent windows

Polycrystalline infrared transparent materials with good optical and mechanical properties are needed for the fabrication of infrared windows and domes. We have developed a synthesis process to produce MgO nanopowders. The average aggregate size of powder is in the range of 150-160 nm, with a narrow aggregate size distribution. Additionally, a protocol for compaction of nanocrystalline powders to achieve high green density (>50% of theoretical density) and microstructural uniformity has been described, as these factors are critical to sinter compacts to theoretical density with minimum number of flaws. Some of the samples were hot pressed and subsequently hot isostatically pressed (HIPed) for complete densification. Processing parameters are discussed to achieve uniformly dense sample with high degree of translucency. Some of the fully densified samples had a grain size as low as 100-300 nm.