The structure of braitschite, a calcium rare earth borate
- George Washington Univ., Washington, DC (United States)
- Smithsonian Inst., Washington, DC (United States)
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); Materials Science of Actinides (MSA)
- Sponsoring Organization:
- USDOE SC Office of Basic Energy Sciences (SC-22)
- DOE Contract Number:
- SC0001089
- OSTI ID:
- 1064909
- Journal Information:
- American Mineralogist, Journal Name: American Mineralogist Journal Issue: 1 Vol. 96; ISSN 0003-004X
- Country of Publication:
- United States
- Language:
- English
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