Fig. 8: Schematic of non-classical crystallization and growth evolution of spherulites (not to scale).
From: Controlled spherulitic crystal growth from salt mixtures
a The spherulites nucleate through a non-classical pathway involving the formation of microsized dense ion clusters, which subsequently crystallize via particle attachment (CPA) by nanocrystals. As growth progresses, the nanocrystals can fuse together, and more stable phases may develop on top of the spherulite as smooth blade-like structures which will crack and transform into the equilibrium phase upon complete dehydration. b The spherulitic morphology evolves from compact forms to highly faceted structures as a function of experimental parameters. High relative humidity (RH) and a large diffusion coefficient (D) allow evolution towards larger, smoother, and more stable morphologies, whereas increased viscosity (η) and higher divalent-ion fractions (x) inhibit crystallization, preserve the out-of-equilibrium metastable spherulitic phase, and promote branching that yields smaller spherulites. This transition highlights the complex interplay between growth kinetics and environmental conditions.
