Energy efficient sintering of high-performance ceramics: Microwave cold sintering process

Ceramic scientists have been dedicated to developing mild condition and energy-efficient ceramic sintering technologies. However, the high melting point of ceramics makes low-temperature, rapid, and pressureless sintering extremely challenging, presenting a key bottleneck restricting their energy-efficient preparation and performance control. Recently, an innovative sintering process-microwave cold sintering-has successfully achieved efficient densification of a variety of high-performance ceramics under mild conditions, providing a new approach to addressing these challenges.

Recently, a joint research team from Xi'an Jiaotong University, Southern University of Science and Technology and Pennsylvania State University has proposed and systematically developed a microwave cold sintering process. This process combines a transient liquid-phase-assisted dissolution-precipitation mechanism with the microwave resonance effect to achieve rapid, low-temperature, pressureless sintering of a wide variety of ceramics, including chlorides, oxides, phosphates, and molybdates.

The team published their work in Journal of Advanced Ceramics on November 24, 2025.

Prof. Jing Guo of Xi'an Jiaotong University, corresponding author of the study, stated, "We introduced a small amount of transient liquid phase and exploited its resonant behavior in a high-frequency microwave field to efficiently convert electromagnetic energy into a sintering driving force. This allowed us to achieve high densification of the ceramic while significantly reducing the sintering temperature and time."

Using transmission electron microscopy (TEM) and phase-field simulation, the research team revealed the densification mechanism of MW-CSP: the transient liquid phase not only promotes particle rearrangement and dissolution-precipitation processes, but its resonant behavior in the high-frequency microwave field also significantly improves the overall heating efficiency and atomic migration rate, thereby synergistically accelerating the densification of the ceramic.

In terms of performance, ceramics prepared via MW-CSP exhibit significant advantages. The Vickers hardness of the MW-CSP NaCl ceramic is 95.2% higher than that of conventionally sintered samples. The Q×f value of the MW-CSP MgMoO₄ ceramic in the microwave range is improved by over 52.8%. Furthermore, the MW-CSP KDP ceramic exhibits ferroelectric phase transition behavior comparable to that of previous works using traditional fabrication methods. Notably, compared with other pressureless sintering techniques, MW-CSP reduces energy consumption by more than 97%, lowers sintering temperatures by 225-500 °C, and shortens sintering time by 12.8-21.5 hours.

"This work not only demonstrates the feasibility and superiority of MW-CSP in preparing various ceramic systems, but more importantly, it opens a new path for preparing low-carbon, energy-efficient, and high-performance ceramics with broad application prospects," concluded Prof. Jing Guo. "We anticipate that more research groups worldwide will expand the range of applicable material systems with energy-efficient sintering."

This research was funded by the Natural Science Foundation of Shaanxi Province (No. 2024JC-YBMS-349), the Guangdong Provincial Key Laboratory Program (No. 2021B1212040001), and the Fundamental Research Funds for the Central Universities. The authors would like to thank the staff at the Instrument Analysis Center of Xi’an Jiaotong University for their help with the XRD, SEM, and Raman measurements. The authors thank Zeming Qi, Hengzhe Liu, and Chuansheng Hu at the IR beamline workstation of the National Synchrotron Radiation Laboratory (NSRL) for their help in the IR measurement.

About Authors

Jing Guo is a professor at the School of Materials Science and Engineering, Xi'an Jiaotong University. He graduated from Xi'an Jiaotong University with a bachelor in Microelectronics in 2009 and a doctorate in Electronic Science and Technology in 2015. From 2013 to 2014, he was a visiting scholar at Pennsylvania State University, where he studied under Prof. Clive A. Randall. He then continued his postdoctoral research at Pennsylvania State University until 2018. Prof. Jing Guo's research focuses on electro-ceramics, cold sintering process, and low temperature co-firing ceramic (LTCC). He has published over 100 papers in internationally renowned journals with over 7,600 citations and H-index of 48. He holds 13 authorized invention patents and serves in various editorial capacities, such as Associate Editor of the Journal of the American Ceramic Society.

Hong Wang is a chair professor and associate provost of Southern University of Science and Technology. She received her bachelor, master and Ph.D degrees in electronic materials and components in 1986, 1990, 1998 from Xi’an Jiaotong University, respectively. Her research interests include dielectric materials for electronic components and ceramic packages, functional nanocomposites for energy storage and electro-magnetic devices, and microwave dielectric measurement technologies. She has been elected to IEEE Fellow in 2020 and received the IEEE Ferroelectrics Recognition Award in 2023.

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