Densification with CSP is mainly ba

Densification with CSP is mainly based on pressure solution mechanism, often encountered in geoscience [25,32]. This mechanism is driven by chemical potential gradients from highly constrained areas with enhanced dissolution and high chemical potential to low constrained areas at particle surfaces with a lower chemical potential, through atomically thin liquid film at the contacting particle surfaces. A discussion of the thermodynamic principles governing pressure solution in cold sintering is made in section II.2.3. The pressure solution is conceptually similar to Coble and Nabarro-Herring creep laws which are driven by grain boundary and intragranular diffusion, respectively [25,32]. However, pressure solution creep occurs at much lower temperatures than these two other mechanisms owing to the diminished activation energy of diffusion lower in liquids and at surfaces relative to bulk diffusion in solids.