Optimization of spray freeze drying parameters for spark plasma sintering of transparent MgAl2O4 spinel

Magnesium aluminate spinel (MgAl₂O₄) is considered as one of the most important spinels possessing desirable mechanical properties, with a wide range of applications at high temperatures. Powder granulation by spray freeze drying can lead to better powder flow and distribution in the mold, resulting in a specimen with high green density and strength. Accordingly, this study aimed at investigating the influential parameters on the granulation process of spinel powders via the spray freezing drying method. At first, spinel powders with various weight percents of 20, 25, 30, 35 and 50, and PVA binders with 0, 1, 2 and 8 wt% were investigated to prepare the optimal solution. Finally, the granules were sintered using the SPS method. The obtained bodies were tested by X-ray diffraction, SEM, FE-SEM, Viscosity and UV–Vis. The results showed that the optimal amount of the binder to obtain uniform granules in this process was 3%. Also, 35 wt% of solid loads represented the optimum amount for slurries, forming granules with the size range of 10–50 μm. By powder granulation, density experienced an increase of about 20%, leading to the growth of more than 15% in the in-line transmission for the IR range.