Very recently, a novel sintering te

Very recently, a novel sintering technology, which is called as cold sintering process (CSP), is established to achieve dense ceramic solids at dramatically reduced sintering temperatures.[16-22] Basically, CSP needs a temporary aqueous environment to accelerate densification by a mediated dissolution–precipitation process under some external pressure ranged from 50MPa to 500MPa.[17] With the assistance of pressure,a proper liquid medium can wet the particle interfaces to dissolve the particle edge, and meanwhile can lead to a facilitated particle rearrangement. Both of these effects will help to increase the density of ceramics compacts. By far, the feasibility of CSP to densify more than 50 chemistries with 80%-99% of theoretical density below the temperature of 300°C have been demonstrated.[16] For some specific ingredients, although they cannot be directly densified through CSP method, the samples proceeded by CSP can be easily fabricated by the following conventional sintering at much lower temperature than usual. For example, benefited from the CSP, Guo et al. successfully reduced the sintering temperature from 1400°C to 1200°C for zirconia ceramics during the following conventional sintering.[20]Congruent dissolution can be observed in this case, and no segregation appeared during the precipitation.[23]For some substances such as BaTiO3, previous studies have revealed an incongruent dissolution phenomenon when BaTiO3 particles are cold sintered with the assist of Ba(OH)2/TiO2 suspension.[24]Dense BaTiO3 ceramics with ~95% relative density containing the carbonate-rich glass phase was first obtained at the low temperature of 180oC via a hydrothermal synthesis assisted cold sintering process, and then was crystallized into BaTiO3 after heat treatment. [17] Whatever congruent or incongruent dissolution is involved, these two methods are derived from cold sintering technique and then followed by conventional sintering or a heat treatment, and can be called as cold sintering assisted sintering (CSAS). It has been proved that CSAS method can play a positive role in increasing the green density of ceramics, and then lowering down the sintering temperatures.