Synthesis of bulk tetragonal zirconia without stabilizer: The role of precursor nanopowders

The densification of undoped zirconia nanopowder was performed using the High-Pressure Field Assisted Sintering technique, with the aim of preparing bulk size-stabilized tetragonal zirconia. The role played by the structural and microstructural properties of the starting powders on the characteristics of the sintered materials was investigated by exploring several different synthetic routes. Nanopowders prepared by solvothermal methods were proven to give the most satisfactory results thanks to their microstructure, particularly characterized by uniform spherical microaggregates. Using solvothermally synthesized powder as a starting material, nearly fully dense (97% relative density) samples of undoped size-stabilized tetragonal zirconia were obtained with a sintering cycle of 5 min under a uniaxial pressure of 700 MPa, at sintering temperatures as low as 900 °C.