Cold sintering process (CSP) change

Cold sintering process (CSP) changes our concept for the fabrication of ceramics due to its extremely low processing temperatures, generally below 300 °C.1,2 Since its discovery, the successful densification of more than 80 ceramic compositions, including binary, ternary and quaternary compounds was demonstrated.3 Besides, new inorganic-based composites with 2D materials,4 carbons,5 polymers6 were fabricated. Nonetheless, there is a lack of studies on doping of ceramics, which is regarded as an effective approach to tailor functional properties of materials.7 In industry, several kinds of additives have been doped into BaTiO3 to achieve desired properties and function, such as positive temperature coefficient of resistivity,8 temperature stability of the relative permittivity,9 high relative permittivity by introducing polar nano regions in perovskite lattice,10 and controlled electronic and ionic conductivity to improve reliability.11,12 Remarkable functionalities were also demonstrated through the fabrication of composites with controlled architectures in the form of 0-3 type composites,13,14 core-shell structures,15 and grain boundary phase segregation.16 To expand on these previous findings to CSP materials and fabricate other novel ceramics, we need a deep understanding of mechanisms allowing lowtemperature densification, namely how starting powders evolve to high dense ceramics under CSP conditions.