Advances and Challenges to the Manufacturing of Electroceramics with Cold Sintering
Cold Sintering continues to provide new insights into a densification process enabled by pressure solution creep, enabled by a transient phase. The transient phase enables the chemo mechanical enhanced dissolution, transport, and precipitation processes. A large variety of ceramics, ceramic composites, and a few metals have all successfully demonstrated cold sintering densification, under pressures of 500 MPa, and temperatures of 350 oC. Here we will review evidence for pressure solution with some initial modelling of the rate-controlled densification kinetics. Currently the major focus has been using ZnO as a model system, but there is also evidence with BaTiO3, and Na2Mo2O7 for pressure solution creep. In addition, to the fundamentals of cold sintering, we will also give insights to the potential of manufacturing with the cold sintering process. Progress to the densification control and reproductivity is being considered with respect to the transient phase, sample aspect ratio, shape, multilayers, heating rate, and uniformity of stress in the die. Sintering involves a transient phase that permits the densification of particulate materials at low temperatures 300 oC and below. Sintering at such low temperature offers so many new opportunities. It permits the integration of metastable materials that would typically decompose at high temperatures. So cold sinter enables a platform for better unification of material science. Now ceramics, metal and polymers can be processed under a common platform in one step processes. With controlling the forming process new nanocomposites can be fabricated. Polymers, gels and nanoparticulates can be dispersed, interconnected and sintered in the grain boundaries of a ceramic matrix phase. Various examples will be given to describe various forms of property changes that can be appreciated from this new method of composite design. Examples will be given around dielectrics, semiconductors, and mixed ionic conductors.