Toward a size scale-up cold sintering process at reduced uniaxial pressure

Cold sintering is a low-temperature powder process methodology that enables the densification of ceramics and ceramic-based composites at significantly reduced times and temperatures. Although the general notion of required pressure for the cold sintering is in the hundreds MPa, some material systems were reasonably demonstrated to be densified in the pressure below 50 MPa, which allows to increase the sample size up to 25 cm² using a small tabletop laboratory press. Indeed, the pressure requirement has been a major constraint on promoting its application deployments, but this study is intended to propose a path to alleviate that limitation. Five different ceramic and composite systems (three ZnO-based composites, Li_1.5Al_0.5Ge_1.5(PO₄)₃, and zeolite Y) with applications in electronic, structural, and energy storage were investigated as a preliminary example of the size scale-up process. One of the observed challenges of the scale-up process was to obtain homogeneous microstructure all over the sample as the transient phase evaporation rate may be different upon the localization. In the case of ZnO, the inhomogeneous pellet translucency may pertain to partial anisotropic grain growth within the same sample.