Preparation of MgO·1.5Al2O3 transparent ceramic by pressureless sintering and hot isostatic pressing

Abstract

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 (Mg0.46Al0.54)IV[Mg0.26Al1.64□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).