Multi‐Step Crystallization of Barium Carbonate: Rapid Interconversion of Amorphous and Crystalline Precursors

The direct observation of amorphous barium carbonate (ABC), which transforms into a previously unknown barium carbonate hydrate (herewith named gortatowskite) within a few hundred milliseconds of formation, is described. In situ X‐ray scattering, cryo‐, and low‐dose electron microscopy were used to...

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Bibliographic Details
Published in:Angewandte Chemie (International ed.) 2017-12, Vol.56 (50), p.16028-16031
Main Authors: Whittaker, Michael L., Smeets, Paul J. M., Asayesh‐Ardakani, Hasti, Shahbazian‐Yassar, Reza, Joester, Derk
Format: Article
Language:English
Subjects:
amorphous materials
Barium
barium carbonate
crystal growth
Crystal structure
Crystallinity
Crystallization
Crystals
Electron microscopy
metastable compounds
multi-step crystallization
Nanoparticles
Precursors
Recrystallization
Vibrational spectra
X-ray scattering
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Description
Summary:The direct observation of amorphous barium carbonate (ABC), which transforms into a previously unknown barium carbonate hydrate (herewith named gortatowskite) within a few hundred milliseconds of formation, is described. In situ X‐ray scattering, cryo‐, and low‐dose electron microscopy were used to capture the transformation of nanoparticulate ABC into gortatowskite crystals, highly anisotropic sheets that are up to 1 μm in width, yet only about 10 nm in thickness. Recrystallization of gortatowskite to witherite starts within 30 seconds. We describe a bulk synthesis and report a first assessment of the composition, vibrational spectra, and structure of gortatowskite. Our findings indicate that transient amorphous and crystalline precursors can play a role in aqueous precipitation pathways that may often be overlooked owing to their extremely short lifetimes and small dimensions. However, such transient precursors may be integral to the formation of more stable phases. The precipitation of witherite (BaCO3) from aqueous solution involves not one, but two precursors: amorphous barium carbonate (ABC) and a crystalline barium carbonate monohydrate (gortatowskite) that crystallizes in a quasi‐2D habit. Both intermediates are very short‐lived and their characterization requires rapid, cryogenic, and/or low‐dose in situ techniques.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201709526