Dense Liquid Precursor in Mineral Crystallization: Spinodal Morphology and High Viscosity Evidenced by Electron Imaging.

Abstract

Recent consensus suggests that the classical single-step nucleation theory, a key reference for nanomaterial synthesis, inadequately explains nanocrystal formation in solutions, as it ignores noncrystalline intermediate structures. Among these, reactant-rich liquid nanostructures have gained attention for their potential to differentiate between crystallization theories. However, capturing their physical properties at the nanometer scale before crystallization remains challenging. We demonstrate that liquid nanostructures in cerium oxalate crystallization exhibit spinodal decomposition-like morphologies, have a viscosity at least 5 orders of magnitude higher than the surrounding water-rich phase, and act as the main nucleation reservoir for the amorphous phase. These findings suggest that models for multistep crystallization must incorporate spinodal morphologies, significant viscosity contrasts between separating phases, and a nucleation process.