Of the various energy-efficient sin

Of the various energy-efficient sintering techniques, the cold sintering process (CSP) holds the most potential for ultra-low temperature sintering. Though most of the CSP papers have been published within the past 5 years, the origin of this technique may be traced back to the 1800s for metals1,2 and 1950-1960s when researchers started to realize the presence of moisture increased the green density in oxides and sulfates which reduced the sintering temperatures.1,3,4 In the 1970-1980s, the word “cold sintering” was first used to refer to a process utilizing “plastic deformation of powder particles in a high pressure gradient at ambient temperature resulting in green densities close to theoretical” for metals, glass, and ionic crystals.5 At the same time, the hydrothermal hot-pressing (HHP) method was proposed for the densification of cement materials at low temperatures.6,7 Kähäri et al. showed Li2MoO4 (LMO) could be sintered at near room temperatures by adding water and higher uniaxial pressures, noting that large particles are beneficial for the densification.8,9 The group at Penn State University outlined the path towards a universal strategy for the cold sintering process in which particles were mixed with a small amounts of solvent (often aqueous or polar organics). This enabled controlled dissolution at low temperatures and applied pressures; subsequently, the solvent is evaporated from the open system.10 In many cold sintering studies, ceramic pellets can be sintered to >95% relative density at