During the past years, many efforts have been devoted to the study and production of high-quality MgO-Y 2O 3 powders. Moreover, the fine grain size of MgO-Y 2O 3 powders, which are essential for obtaining fine grains and uniform microstructures, will positively influence the final sinterability. This is because the addition of MgO will be helpful in inhibiting grain growth, and then the grain size of the transparent ceramic will be smaller than that of the yttrium ceramics without MgO addition. Among these yttrium-oxide-based transparent ceramics, MgO-Y 2O 3 has been reported to present a better performance than pure Y 2O 3 ceramics or pure MgO ceramics, owing to its better optical transmittance, thermal shock resistance and mechanical strength. In recent years, many investigations have focused on Y 2O 3-based transparent ceramics, which are proven to be promising window materials because of their wide band transmission, low infrared emissivity, low scattering and good mechanical properties. The mid-infrared window materials that are applied to hypersonic aircraft windows require excellent service performances at a high temperature.
Transparent ceramics are a candidate for many applications, such as mid-infrared window materials, owing to their excellent mechanical, thermal and optical properties.
The present study may open an avenue for developing transparent ceramics based on MgO-Y 2O 3 nanopowders prepared by hydrothermal technique. Furthermore, the ceramics prepared with the above powders displayed a homogenous two-phase microstructure, fewer pores and a fine grain size with Y 2O 3 of ~1 µm and MgO of ~620 nm. The results show that powders with a seed content of 5% that are hydrothermally synthesized at 190 ☌ can present a better uniformity and dispersion with a particle size of ~125 nm.
Y(NO 3) 3♶H 2O, Mg(NO 3) 2♶H 2O, Y 2O 3 seeds and MgO seeds were used as raw materials to prepare the MgO-Y 2O 3 composite powders (50:50 vol.%), and the influences of the seed contents and hydrothermal treatment temperatures on the final powders and hot-pressed ceramics were investigated by XRD, SEM and TEM techniques. In this study, the combination of hydrothermal technique and seed-doping method was conducted to coordinately control the formation of fine MgO-Y 2O 3 powders, which are promising mid-infrared materials applied to hypersonic aircraft windows due to their excellent infrared transmissions over wide regions.
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