Comparisons of grain size-density trajectory during spark plasma sintering and hot-pressing of zirconia

Spark plasma sintering (SPS) and hot-pressing (HP) of a granulated stabilized zirconia powder have been investigated for a fixed macroscopic compaction pressure of 100 MPa and a fixed heating rate (25 °C/min for HP, 50 °C/min for SPS). The “relative density/grain size” trajectories have been established for both sintering methods.HP is shown to be similar to SPS for the manufacturing of polycrystalline TZ3Y materials with a final grain size well below the micrometer. Independently of the sintering technology employed, it is interesting to note that three kinds of microstructures are obtained depending on the experimental parameters: porous materials (opened porosity, relative density between 61 and 90%) with a nanometer grain size (around 75-80 nm), dense materials (closed porosity, relative density between 90 and 98%) with a nanometer grain size (around 75-80 nm), fully dense material with a submicron grain size (around 160 nm using SPS and around 105 nm using HP).