Densification of water-insoluble Li ₂TiO ₃ nanoceramics via a cold sintering process using water as a transient liquid phase

The cold sintering process (CSP) is an advanced low-temperature sintering technology whose effectiveness is closely related to the selection of transient liquid phases (TLP). While water serves as an ideal TLP for water-soluble ceramics, most water-insoluble materials necessitate acids, bases, or specialized solvents instead. This limitation has severely restricted the application of CSP, as many water-insoluble ceramics cannot be densified due to the lack of suitable TLP. This study demonstrates a breakthrough approach that exploits nanoscale effects to enable water to act as an effective TLP for the densification of water-insoluble Li₂TiO₃ ceramics. Comparing nano (19.71 nm) and micro-scale Li₂TiO₃ powders under identical sintering conditions revealed that, despite Li₂TiO₃’s exceptionally low aqueous solubility, nanopowders achieved 94.33% relative density at merely 300°C and 700 MPa, whereas micropowders attained only 78% density. Further analysis revealed a distinctive densification mechanism that integrates dislocation-mediated plastic deformation with localized dissolution phenomena at nanoparticle interfaces. The resultant nanoceramics exhibited superior Vickers hardness (905 HV) and enhanced electrical conductivity compared to conventional sintering (1000°C), while maintaining a refined nanoscale grain structure (26.42 nm). This study established an effective strategy for the cold sintering of water-insoluble ceramics with layered structures using water as a TLP, significantly expanding the applicability of CSP technology and offering new pathways for energy-efficient fabrication of advanced functional ceramics.