FABRICATION OF POLYCRYSTALLINE TRANSPARENT CERAMICS BY A COMBINATION OF SPARK PLASMA SINTERING (SPS) AND HOT ISOSTATIC PRESSING (HIP) PROCESSES

SPS is a rapid and cost-effective advanced sintering technique, highly promising for the fabrication of transparent polycrystalline ceramics. However, using this approach for large and/or thicker parts is difficult due to limited tooling dimensions, applied force and non-homogeneous temperature distribution. In the present study we suggest to combine the SPS process with a subsequent HIP treatment to obtain relatively large (40 mm diameter) transparent ceramic parts. MgAl₂O₄ and YAG nano-size powders, were firstly densified by SPS to obtain translucent parts with about 1-2% of residual porosity. After the HIP treatment at 1800ºC, under 2000 atm for 10 hours, samples were fully dense with transparency of about 80% in the 600nm wave length.