Co‐sintering ceramic and thermoplastic polymer composites in a single step with very high volume fractions of ceramics seems unlikely, given the vast differences in the typical sintering temperatures of ceramics versus polymers. These processing limitations are overcome with the introduction of a new sintering approach, namely “cold sintering process” (CSP). CSP utilizes a transient low temperature solvent, such as water or water with dissolved solutes in stoichiometric ratios consistent with the ceramic composition, to control the dissolution and precipitation of ceramics and effect densification between room temperature and ≈200 °C. Under these conditions, thermoplastic polymers and ceramic materials can be jointly formed into dense composites. Three diphasic composite examples are demonstrated to show the overall diversity of composite material design between organic and inorganic oxides, including the microwave dielectric Li2MoO4–(C2F4 ) n , electrolyte Li1.5Al0.5Ge1.5(PO4)3–(CH2CF2 ) x [CF2CF(CF3)] y , and semiconductor V2O5–poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate composites. Cold sintering is more general and shall have a major impact on the processing of composite materials for many different applications, mechanical, thermal, and electronic, to mention a few possibilities. CSP concepts open up new composite material design and device integration schemes, impacting a wide variety of applications.

Ceramic-polymer composites are of interest for designing enhanced and unique properties. However, the processing temperature windows of sintering ceramics are much higher than that of compaction, extrusion, or sintering of polymers, and thus traditionally there has been an inability to cosinter ceramic-polymer composites in a single step with high amounts of ceramics. The cold sintering process is a low-temperature sintering technology recently developed for ceramics and ceramic-based composites. A wide variety of ceramic materials have now been demonstrated to be densified under the cold sintering process and therefore can be all cosintered with polymers from room temperature to 300 °C. Here, the status, understanding, and application of cold cosintering, with different examples of ceramics and polymers, are discussed. One has to note that these types of cold sintering processes are yet new, and a full understanding will only emerge after more ceramic-polymer examples emerge and different research groups build upon these early observations. The general processing, property designs, and an outlook on cold sintering composites are outlined. Ultimately, the cold sintering process could open up a new multimaterial design space and impact the field of ceramic-polymer composites.

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