MgO·1.5Al2O3透明陶瓷的无压/热等静压烧结制备

镁铝尖晶石透明陶瓷是典型的结构功能一体化材料, 具有优异的光学和机械性能。实验合成了颗粒细小、均匀的单相MgO·1.5Al₂O₃陶瓷粉末, 并且利用XRD全谱拟合软件Fullprof和尖晶石位置分配程序SIDR两步法确定其晶体结构为(Mg_0.46Al_0.54)^IVMg_0.26Al_1.64□_0.09]^VIO₄。再通过真空无压烧结结合热等静压烧结制备出了高性能的透明陶瓷, 热等静压18 MPa下1850℃烧结4 h所得样品的致密度达到99.75%, 厚度为2 mm的烧结样品可见光透过率达到65%, 红外波段透过率达到80%以上, 维氏硬度为(12.75±0.12) GPa, 杨氏模量为277 GPa。

Preparation of MgO·1.5Al2O3 Transparent Ceramic by Pressureless Sintering and Hot Isostatic Pressing

Possessing unique optical and mechanical properties, magnesium aluminate spinel transparent ceramic has been regarded as an important multifunctional material. In this study, pure phase MgO·1.5Al₂O₃ ceramic powders with uniform and fine particle size were synthesized through solid-state reaction. A two-step structural refinement procedure, including XRD Rietveld analysis by Fullprof software and further refinement by spinel solid solutions structure modeling program SIDR, was utilized to resolve the crystal structure of synthesized powders. After refinement, the crystal structure was finally determined to be (Mg_0.46Al_0.54)^IVMg_0.26Al_1.64□_0.09]^VIO₄. Using the synthesized MgO·1.5Al₂O₃ ceramic powders, high performance transparent ceramic was fabricated by pressureless vacuum sintering and subsequent hot isostatic pressing sintering (HIP). The relative density of the sample HIP-sintered at 1850 ℃ for 4 h under 180 MPa Ar could reach 99.75%. In the meantime, the in-line transmittance measurement of the 2-mm-thick sample displayed good optical transparency from ultraviolet to middle-infrared wavelengths with the maximum transmittance 65% in visible region and 80% in infrared region. The MgO·1.5Al₂O₃ transparent ceramic also exhibited good mechanical properties of Vickers hardness ((12.75 ± 0.12) GPa) and Young's modulus (277 GPa).