Crystal structures and phase transformations in Ca(BH4)2
(2009) Acta Materialia — Vol. 57, n° 3, p. 732-738 (2009)
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- Abstract
- Crystal structures of three polymorphs of Ca(BH4)2, and related phase transitions, have been identified. Removal of solvent from Ca(BH4)2·2THF results in various mixtures of α- and β-polymorphs of Ca(BH4)2. These mixtures were studied by in situ synchrotron powder diffraction in argon atmosphere. The α-Ca(BH4)2 structure crystallizes in the noncentrosymmetric space group F2dd, and contains an ordered BH4 - anion. Upon increasing the temperature, the cell parameters a and c of the α-phase approach each other, and at ∼495 K, a second order α → α′ transition takes place resulting in a tetragonal α′-phase of space group I-42d, a supergroup of F2dd. The structure of β-Ca(BH4)2, which is 3.7-5.6% denser depending on temperature, was described in space group P-4. Crystal structures, variation of the cell parameters, and weight fraction are reported for the three Ca(BH4)2 phases as a function of temperature. © 2008 Acta Materialia Inc.
- Affiliations
ESRF, Grenoble (France) Chimie
Citations
Filinchuk, Y., Rönnebro, E., & Chandra, D. (2009). Crystal structures and phase transformations in Ca(BH4)2. Acta Materialia, 57(3), 732-738. https://doi.org/10.1016/j.actamat.2008.10.034 (Original work published 2009)