Breakthrough in cold sintering process: Water enables low-temperature densification of water-insoluble Li2TiO3 ceramics

Ceramics are indispensable in electronics, energy storage, and advanced engineering, but their production often relies on high-temperature sintering that consumes massive energy and degrades material performance. The cold sintering process (CSP) has emerged as a game-changer, allowing densification at low temperatures (below 300 °C) using transient liquid phase (TLP) to facilitate particle bonding. However, a major roadblock has persisted: water, an ideal TLP for water-soluble ceramics, fails for most water-insoluble materials, which require harsh acids, bases, or expensive solvents instead. This limitation has shut out countless important ceramics from CSP’s benefits.

Li₂TiO₃ is one such critical material. Valued for its roles in solid electrolytes, microwave devices, and nuclear tritium breeders, it suffers from traditional high-temperature sintering: elevated temperatures (around 1000°C) cause grain coarsening and lithium volatilization, weakening its ionic conductivity and structural stability.

Now, a joint team consisting of researcher Ruichong Chen from Chengdu University, Professor Jianqi Qi from Sichuan University, and researcher Haomin Wang from Taihang Laboratory made a breakthrough: By shrinking Li₂TiO₃ powders to the nanoscale, they enabled water to act as an effective TLP for cold sintering, despite the material’s near-insolubility in water.

This work was published in the Journal of Advanced Ceramics on July 12, 2025.

“We’ve long known that nanomaterials behave differently—their high surface energy and unique interfaces can unlock new properties,” said Ruichong Chen, the first corresponding author from Chengdu University. “Here, we harnessed these nanoscale effects to bypass solubility limits, letting water do the work that once required harsh chemicals.”

The team compared nano-sized (19.71 nm) and micro-sized Li₂TiO₃ powders under identical CSP conditions. At 300°C and 700 MPa, the nanopowders achieved a remarkable 94.33% relative density, while microsized powders reached only 78%. High-resolution microscopy revealed the secret: a unique densification mechanism combining dislocation-mediated plastic deformation (where pressure drives atomic rearrangement) and localized dissolution at nanoparticle interfaces—phenomena amplified by the nanoparticles’ high surface energy.

The result? Nanoceramics with a refined grain structure (26.42 nm) that outperformed their traditionally sintered counterparts. They exhibited a Vickers hardness of 905 HV—far exceeding the hardness of ceramics made via conventional 1000°C sintering—and enhanced electrical conductivity, critical for energy and electronic applications.

“Traditional sintering of Li₂TiO₃ at 1000°C coarsens grains and causes lithium loss, undermining performance,” noted Leiqing Tang, the first author from Chengdu University. “Our cold-sintered nanoceramics retain their fine structure and chemical stability, all while using less energy and simpler, greener solvents—just water.”

This approach not only solves a long-standing problem in CSP but also opens doors for other water-insoluble ceramics. By eliminating the need for specialized solvents, it simplifies manufacturing, reduces costs, and aligns with global trends toward sustainable “green” fabrication.

The team published their findings in the Journal of Advanced Ceramics. Future work will explore applying this strategy to other functional ceramics, expanding the reach of CSP in energy, electronics, and beyond.

About Author

Ruichong Chen, PhD in Science, is currently a distinguished researcher at Chengdu University. He holds a joint PhD in Condensed Matter Physics from Sichuan University and Energy Chemical Engineering from Kyushu University, Japan. His main research interests include structural design and performance optimization of solid tritium breeders in the field of magnetic confinement nuclear fusion, and controllable preparation of hollow target pellets for B₄C ignition in the field of laser inertial confinement nuclear fusion. He has published more than 40 papers in prestigious international journals including Nuclear Fusion, Advanced Functional Materials, Journal of Advanced Ceramics, Journal of the American Ceramic Society, and Journal of Nuclear Materials. Additionally, the researcher holds three authorized national invention patents.

Jianqi Qi, PhD, currently a doctoral supervisor at Sichuan University. His main research directions are the design and preparation of advanced functional materials, research on the service performance of materials under extreme conditions, and design and regulation of material systems and microstructures. He has undertaken more than 20 projects including the National Natural Science Foundation of China and national key research and development projects, published more than 190 papers in multiple international journals, participated in the application of more than 10 patents, and won the second prize of Sichuan Science and Technology Progress Award. He also serves as an editorial board member of journals such as "Journal of Advanced Ceramics" and "Modern Technical Ceramics" and a young editorial board member of journals such as "Journal of Rare Earths".

Haomin Wang is a postdoctoral fellow at Nanyang Technological University, Singapore. He is a member of the Chinese Society of Mechanics, the American Society of Mechanical Engineers (ASME), and the Sichuan Society of Mechanics. He has been selected into the "High-level Talent Cultivation Program" of Chengdu University. His main research areas are nanomaterial preparation and mechanical behavior, 3D printing metamaterials, and micro-nanomechanics. He has published more than 50 SCI papers in top international journals such as Nature Communications, has 5 authorized invention patents, and is currently in charge of 4 national and provincial projects.

About Journal of Advanced Ceramics

Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen. JAC’s 2024 IF is 16.6, ranking in Top 1 (1/33, Q1) among all journals in “Materials Science, Ceramics” category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508