OPTIMIZATION OF THE SPARK PLASMA SINTERING CONDITION FOR TRANSPARENT POLYCRYSTALLINE MAGNESIUM ALUMINATE SPINEL

摘要

Polycrystalline transparent magnesium aluminate spinel is a promising candidate for light weight transparent armor and infrared window applications. The spark plasma sintering (SPS) technique has been used to produce a fine-grain microstructure which potentially yields a high hardness value for spinel. By controlling the SPS heating rate at ≤ 2.5°C/min up to 1350°C with a 10 minute hold, an in-line transmittance of ＞60% at the 550 nm wavelength could be attained for a 1.8 mm-thick spinel sample. The current work demonstrates that, the SPS heating rate is the decisive factor in attaining a high transparency for the polycrystalline spinel produced from a high-purity starting powder. Experimental data also showed that a long SPS processing time might diminished the transmittance of spinel.