The structure of braitschite, a calcium rare earth borate

Journal Article · Wed Dec 22 04:00:00 EST 2010 · American Mineralogist

DOI:https://doi.org/10.2138/am.2011.3592· OSTI ID:1386729

Rowland, C. E.; Cahill, C. L.; Post, J. E.

The crystal structure of braitschite, Ca6.15Na0.85RE2.08[B6O7(OH)3(O,OH)3]4(H2O), is reported here in space group P6/m with unit-cell parameters a = 12.1506(6), c = 7.3678(4) Å, and V = 942.03(8) Å3. Data were collected from a single crystal using a MoKα source and a CCD detector, solved by direct methods, and refined to an R factor of 2.81%. The mineral structure consists of hexaborate fundamental building blocks that polymerize along [001] and are bound by Ca2+ and REE3+ counter-ions. The framework forms hexagonal channels, which are occupied alternately by Ca2+ cations and water molecules. In an investigation of its thermal stability, braitschite maintains its crystallinity to a temperature of 400 °C, after which it undergoes decomposition. Using Rietveld refinements against powder X-ray diffraction data, we were able to track the loss of water molecules in channels and hydroxyl groups in the covalent B-O network with increasing temperature.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA)
• Sponsoring Organization: USDOE SC Office of Basic Energy Sciences (SC-22)
• DOE Contract Number: SC0001089
• OSTI ID: 1386729
• Journal Information: American Mineralogist, Journal Name: American Mineralogist Journal Issue: 1 Vol. 96; ISSN 0003-004X
• Publisher: Mineralogical Society of America
• Country of Publication: United States
• Language: English

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synthesis (novel materials)
synthesis (self-assembly)