Thermal polymorphism and decomposition of Y(BH4)3
(2010) Inorganic Chemistry — Vol. 49, n° 8, p. 3801-3809 (2010)
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- Abstract
- The structure and thermal decomposition of Y(BH4)3 is studied by in situ synchrotron radiation powder X-ray diffraction (SR-PXD), 11B MAS NMR spectroscopy, and thermal analysis (thermogravimetric analysis/differential scanning calorimetry). The samples were prepared via a metathesis reaction between LiBH4 and YCl3 in different molar ratios mediated by ball milling. A new high temperature polymorph of Y(BH4)3, denoted β-Y(BH4)3, is discovered besides the Y(BH4)3 polymorph previously reported, denoted ∝-Y(BH4)3. β-Y(BH 4)3 has a cubic crystal structure and crystallizes with the space group symmetry Pm̄3m and a bisected a-axis, a = 5.4547(8) Å, as compared to ∝-Y(BH4)3, a = 10.7445(4) Å (Pā3). β-Y(BH4)3 crystallizes with a regular ReO3-type structure, hence the Y3+ cations form cubes with BH4 - anions located on the edges. This arrangement is a regular variant of the distorted Y3+ cube observed in ∝-Y(BH4)3, which is similar to the high pressure phase of ReO3. The new phase, β-Y(BH4)3 is formed in small amounts during ball milling; however, larger amounts are formed under moderate hydrogen pressure via a phase transition from ∝- to β-Y(BH4)3, at ∼180 °C. Upon further heating, β-Y(BH4)3 decomposes at ∼190 °C to YH 3, which transforms to YH2 at 270 °C. An unidentified compound is observed in the temperature range 215-280 °C, which may be a new Y-B-H containing decomposition product. The final decomposition product is YB4. These results show that boron remains in the solid phase when Y(BH4)3 decomposes in a hydrogen atmosphere and that Y(BH4)3 may store hydrogen reversibly. © 2010 American Chemical Society.
- Affiliations
ESRF, Grenoble (France) Chimie
Citations
Ravnsb k, D. B., Filinchuk, Y., Cerný, R., Ley, M. B., Haase, D., Jakobsen, H. J., Skibsted, J., & Jensen, T. R. (2010). Thermal polymorphism and decomposition of Y(BH4)3. Inorganic Chemistry, 49(8), 3801-3809. https://doi.org/10.1021/ic902279k (Original work published 2010)