Silicon nitride (Si₃N₄) is an excellent candidate for engineering ceramics; however, its toughness and hardness remain fundamentally constrained by the inherent limitations arising from the incompatible α-phase (characterized by high hardness) and β-phase (characterized by high toughness). Herein, we report the exploration of advanced Si₃N₄ ceramics enabled by an intergrown cluster microstructure, which achieves a synergistic enhancement in both toughness (10.2±0.3 MPa·m^1/2) and Vickers hardness (20.1±0.3 GPa). These synergistic properties represent the state-of-the-art among Si₃N₄ ceramics fabricated via liquid-phase sintering reported to date. The formation of columnar clusters is driven by a high-pressure-induced coarsening process. The established metastable growth mechanism may open an avenue for fabricating new-generation Si₃N₄ ceramics with superb performance.

Field-assisted sintering technology has revolutionized material processing by integrating temperature, mechanical, electrical, and magnetic fields to achieve unprecedented densification efficiency and microstructural control. Recent advances in techniques such as hot oscillatory pressing, cold sintering, high/ultra-high pressure sintering, spark plasma sintering, ultrafast high-temperature sintering, and flash sintering have enabled the fabrication of previously unattainable materials, including ultrafine-grained ceramics, nanostructured composites, and functionally graded materials. These materials possess exceptional performances under extreme conditions, expanding applications in aerospace, electronics, energy, and biomedicine. However, the rapid development of these methods has exposed limitations in conventional sintering theory, particularly in describing mass transport and interface evolution under multi-physics coupling. This review systematically examines representative field-assisted sintering technologies and discusses their principles, equipment configurations, and application cases. By analyzing current challenges and opportunities, we aim to bridge fundamental understanding with industrial implementation, providing insights for the design and fabrication of next-generation high-performance materials.

The nacreous layer of shells has become an excellent biomimetic template of materials due to its unique structure. Inspired by the highly complex multilayered structure of shells, biomimetic layered composite protective materials with outstanding strength, toughness, and impact resistance have been developed. As the hard phase in biomimetic pearlescent layered protective materials, ceramics suffer from inherent low toughness. Applying prestress proved to be an efficient method to enhance their toughness and impact resistance. In this study, prestressed biomimetic periodic laminated (TiB₂—TiB)/Ti protective materials were fabricated with spark plasma sintering (SPS) technology under the conditions of 1450 ℃ and 30 MPa in an argon atmosphere. Moreover, both experimental and numerical simulation analyses were conducted to investigate their protective performance. Compared to non-prestressed protective materials, the prestressed constrained materials exhibited the significantly improved protective performance with reduced penetration depth, substantially lower residual velocity, and kinetic energy after impact. This study provided valuable insights into the structural design and performance optimization of other protective materials.

The presence of high-density defects is rarely observed in bulk 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramics obtained through conventional pressureless sintering. In the present work, fine-grained dense 147 nm 3Y-TZP ceramics were prepared by pressureless sintering of commercial 0.25 wt% alumina-doped zirconia powders at 1300 ℃. A novel discovery was reported in which large amounts of defects were present in the grain interiors of the sample. The phenomenon was further examined using three types of powder samples, and the reasons for defect formation were investigated by microstructural characterization using high-resolution transmission electron microscopy (HRTEM) analysis and Rietveld refinement. The results confirmed the essential dependence of the defect formation on the alumina addition. The authors attributed the defect formation to the significant difference in ionic radii of the solvent and solute during the dissolution of alumina into the zirconia lattice. The sintering kinetics were proposed to be enhanced by the presence of substantial defects, which consequently favored the low-temperature sintering of the alumina-doped zirconia ceramics.