A conceptual change in crystallisation mechanisms of oxide materials from solutions in closed systems

Abstract

Atomic and molecular level interactions in solutions dictate the structural and functional attributes of crystals. These features clearly dictate the properties of materials and their applicability in technologies. However, the microscopic phenomena of particle formation—nucleation and growth—in real systems are still not fully understood. Specifically, crystallisation occurring in closed systems are largely unproven. Combining coherent experimental data, we here demonstrate a fundamental nucleation-growth mechanism that occurs in a model zinc oxide system when particles are formed under continuous, rapid heating under closed reaction conditions. Defying all previous reports, we show that the nucleation commences only when the heating is terminated. A prenucleation clusters pathway is observed for nucleation, followed by crystallite assembly-growth. We show that the nucleation-growth processes result from temporal and dynamic activity of constituent ions and gaseous molecules in solution and by the irreversible expulsion of the dissolved gaseous molecules. We suggest that this nucleation process is generic to most closed systems that go through precipitation, and, therefore, important for the crystallisation of a variety of metal oxides, composites and minerals. We anticipate that the work may be a platform for future experimental and theoretical investigation promoting deeper understanding of the nucleation-growth phenomena of a variety of practical systems.

ZnO Multilayer Thin Films as The Seed Layer for ZnO Nanorods: Morphology, Structural and Optical properties

“…It could be proved from the XRD spectra in Figure 11 5-Layers sample has a broader peak compared with the 3 and 4-Layers samples. Other than that, there are reported studies that state that the variation in crystallite is due to the aggregation and recrystallization during the crystal growth process, including heat structure (McGinty et al, 2020;Padmanabhan et al, 2020).…”

Exploration of anion effects in solvothermal synthesis using in situ X-ray diffraction

“…8,52,53 This question is closely related to the mechanism of formation, of which multiple types are reported with varying complexity and strong dependence on the chemical system in question. 54–62 While the crystallization process for specific chemical systems has been shown to consist of condensation of pre-nucleation clusters with product-like atomic structure, the role of anions in stabilizing and directing atomic structure is still poorly understood. Several chemical systems obtain medium-range order upon mixing of reactants in preparation of the precursor 25,63–68 and likely just need sufficient thermal energy to realize long range order.…”