Sintering dense nanocrystalline 3 mol% Yttria stabilized zirconia via high‑pressure spark plasma sintering

This study demonstrates bulk nanocrystalline 3 mol% yttria-stabilized zirconia (3YSZ) fabricated from 60 nm powder by high-pressure spark plasma sintering (HP-SPS). Sintering at 1200 °C under 150 MPa yields a uniform grain size of 65 ± 20 nm, whereas a conventional SPS reference at 50 MPa shows a coarser grain size of 106 ± 47 nm. Under high pressure, densification is driven by grain rotation, rearrangement, and plastic deformation arising from the synergistic action of high pressure and electric fields. The resulting ceramics feature low-energy, flat, ultra-thin grain boundaries and coincidence site lattice (CSL, Σ = 7), delivering outstanding properties: flexural strength of 1703 ± 95 MPa and Vickers hardness of 15.75 ± 0.79 GPa, far exceeding the conventional SPS sample (802 ± 63 MPa, 12.94 ± 0.40 GPa). This work significantly advances processing strategies for manufacturing dense nanocrystalline ceramics with precisely controlled microstructures.