The development of morphology and structure in hexagonal vaterite

Area of Science:

• Biomineralization
• Materials Science
• Crystallography

Background:

• Biomimetic synthesis aims to replicate complex CaCO(3) structures.
• Additives control crystal morphology by selectively inhibiting crystal faces.
• The amorphous-to-crystalline transition in CaCO(3) formation is not fully understood.

Purpose of the Study:

• To elucidate the amorphous-to-crystalline transition during vaterite formation.
• To investigate the role of ammonium ions in vaterite crystal growth.
• To detail the simultaneous development of order and morphology.

Main Methods:

• Cryogenic transmission electron microscopy (cryoTEM).
• Techniques included bright field imaging, cryo-tomography, low dose electron diffraction, and cryo-darkfield imaging.
• Studied vaterite crystal formation in the presence of NH(4)(+) ions.

Main Results:

• Hexagonal vaterite forms via an amorphous precursor phase.
• The amorphous phase undergoes a solid-state transformation into crystalline vaterite.
• Polycrystalline vaterite transitions into a single crystal, templated by an NH(4)(+)-induced crystal plane.

Conclusions:

• Ammonium ions direct the solid-state transformation of amorphous calcium carbonate to single-crystal vaterite.
• Simultaneous development of order and morphology is key in this biomimetic process.
• Understanding this transition offers insights into biomineralization and synthetic crystal growth.