Abstract: A series of transparent spinel ceramics were prepared by a two-step sintering process, vacuum sintering followed by hot isostatic pressing. Phase analysis of the powders and the ceramics were performed by X-ray Diffraction (XRD). The calcined Mg_((1-3χ))Al_((2-2χ))O_4 powders with 0≤χ≤0.20 are mono-phased spinel structure. SEM images show that corundum grains deposited on the main grain boundaries, which are beneficial for toughening the ceramics. Taking consideration of transparency and toughening effect of corundum, the microstructure of the ceramic prepared using Mg_((1-3χ))Al_((2-2χ))O_4 powder with χ of 0.14 is expected better for toughening and strengthening ceramic at less expense of transmittance.

Key words: Mg_((1-3χ))Al_((2-2χ))O_4;transparent ceramics;off-stoichiometric;microstructure;toughening