Reactive Spark Plasma Sintering of Y3Al5O12-MgAl2O4 Composites

In this study, Y3Al5O12-MgAl2O4 (YAG-Spinel) composites, with different molar ratios (1:1 and 1:3), were in-situ fabricated using Reactive Spark Plasma Sintering (RSPS) technique. To this end, Al2O3, MgO, and Y2O3 powders were used as the starting materials. In-situ formation of YAG-Spinel composites was investigated based on the reaction 3.5 Al2O3 + MgO + 1.5 Y2O3 → Y3Al5O12 + MgAl2O4. Both synthesis and densification processes were accomplished using a single-cycle RSPS with one-step heating. The RSPS process was performed at a sintering temperature of 1300 °C for 30 min hold time with a maximum uniaxial pressure of 90 MPa under vacuum conditions. The synthesized phases and microstructures were investigated by X-ray diffraction and field emission scanning electron microscopy. The unwanted phases such as YAP (YAlO3) in a composite microstructure were removed using LiF additive. LiF was used as a sintering aid in the process of sintering. The in-situ synthesized YAG-Spinel composites exhibited no internal infrared transmittance over the infrared wavelength ranges of 2.5-25 μm.