Cold Sintering: Progress, Challenges, and Future Opportunities

TLDR

Cold sintering densifies ceramic powders at temperatures far below their melting points by applying uniaxial force to a transient liquid transport phase, enabling high‑density monoliths and revealing rich mass‑transport behavior at liquid‑solid interfaces. The article summarizes cold sintering achievements and discusses future fundamental and engineering directions. The authors review current working models that describe the operative mechanisms of cold sintering relative to other low‑temperature densification strategies. Observations indicate a multi‑stage densification process similar to liquid‑phase sintering, with grain growth following classical trends but lower activation energies, and low temperatures enabling novel grain‑boundary designs and nanocomposites.

Abstract

Cold sintering is an unusually low-temperature process that uses a transient transport phase, which is most often liquid, and an applied uniaxial force to assist in densification of a powder compact. By using this approach, many ceramic powders can be transformed to high-density monoliths at temperatures far below the melting point. In this article, we present a summary of cold sintering accomplishments and the current working models that describe the operative mechanisms in the context of other strategies for low-temperature ceramic densification. Current observations in several systems suggest a multiple-stage densification process that bears similarity to models that describe liquid phase sintering. We find that grain growth trends are consistent with classical behavior, but with activation energy values that are lower than observed for thermally driven processes. Densification behavior in these low-temperature systems is rich, and there is much to be investigated regarding mass transport within and across the liquid-solid interfaces that populate these ceramics during densification. Irrespective of mechanisms, these low temperatures create a new opportunity spectrum to design grain boundaries and create new types of nanocomposites among material combinations that previously had incompatible processing windows. Future directions are discussed in terms of both the fundamental science and engineering of cold sintering.