Effect of volume ratio on the performance of mid-wave infrared transparent Gd2O3–MgO composite ceramics

Gd2O3–MgO composite ceramics are promising candidates for preparing protective mid-wave infrared (MWIR) windows. However, owing to the different crystal structures of Gd2O3 and MgO after the sintering process, the volume ratio of the two phases must be controlled more precisely to achieve optimum performance. In this study, a nitrate-citrate combustion method was used to prepare Gd2O3–MgO nanopowders with different volume ratios, and composite ceramics were then fabricated via low-temperature pre-sintering and subsequent hot isostatic pressing (HIP). The effect of the Gd2O3:MgO volume ratio on the sintering behaviour, microstructures and optical, thermal and mechanical properties of the composite ceramics was studied in detail. A comprehensive assessment of the above-mentioned properties indicated that the Gd2O3–MgO composite ceramic with a volume ratio of 2:3, which exhibited a transmittance of 80.1–85.8% in the range of 3–5 μm, thermal conductivity of 17.5 W m−1 K−1, Vickers hardness of 9.8 GPa and toughness of 1.84 MPa m1/2, displays the optimum application performance for MWIR windows.