Structure and Dynamics for LiBH4-LiCl Solid Solutions
(2009) In Chemistry of Materials 21(24). p.5772-5782- Abstract
- A Surprisingly high degree of structural and compositional dynamics is observed in the system LiBH4-LiCl as a function of temperature and time. Rietveld refinement of synchrotron radiation powder X-ray diffraction (SR-PXD) data reveals that Cl- readily substitutes for BH4- in the Structure of LiBH4. Prolonged heating a sample of LiBH4-LiCl (1:1 molar ratio) above the phase transition temperature and below the melting point (108 < T < 275 degrees C) can produce highly chloride substituted hexagonal lithium borohydride, h-Li(BH4)(l-x)Cl-x, e.g., x similar to 0.42, after heating from room temperature (RT) to 224 degrees C at 2.5 degrees C/min. LiCl has a higher solubility in h-LiBH4 its compared to orthorhombic lithium borohydride,... (More)
- A Surprisingly high degree of structural and compositional dynamics is observed in the system LiBH4-LiCl as a function of temperature and time. Rietveld refinement of synchrotron radiation powder X-ray diffraction (SR-PXD) data reveals that Cl- readily substitutes for BH4- in the Structure of LiBH4. Prolonged heating a sample of LiBH4-LiCl (1:1 molar ratio) above the phase transition temperature and below the melting point (108 < T < 275 degrees C) can produce highly chloride substituted hexagonal lithium borohydride, h-Li(BH4)(l-x)Cl-x, e.g., x similar to 0.42, after heating from room temperature (RT) to 224 degrees C at 2.5 degrees C/min. LiCl has a higher solubility in h-LiBH4 its compared to orthorhombic lithium borohydride, o-LiBH4, which is illustrated by a LiBH4-LiCl (1:1) sample equilibrated at 245 degrees C for 24 days and left at RT for another 13 months. Rietveld refinement reveals that this sample contains o-Li(BH4)(0.91)Cl-0.09 and LiCl. This illustrates a significantly faster dissolution of LiCl in h-LiBH4 its compared to a slower segregation of LiCl from o-LiBH4, which is also demonstrated by in situ SR-PXD from three cycles of heating and cooling of the same Li(BH4)(0.91)Cl-0.09 sample. The substitution of the smaller Cl- for the larger BH4- ion is clearly observed as a reduction in the unit cell volume as a function of time and temperature. A significant stabilization of h-LiBH4 is found to depend on the degree of anion substitution. Variable temperature solid-state magic-angle spinning (MAS) Li-7 and B-13 NMR experiments oil pure LiBH4 show an increase in full width at half maximum (fwhm) when approaching the phase transition from o- to h-LiBH4, which indicates an increase of the relaxation rate (i.e. T-2 decreases). A less pronounced effect is observed for ion-substituted Li(BH4)(1-x)Cl-x, 0.09 < x < 0.42. The MAS NMR experiments also demonstrate a higher degree of motion in the hexagonal phase, i.e., fwhm is reduced by more than a Factor of 10 at the o- to h-LiBH4 phase transition. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1532752
- author
- Arnbjerg, Lene M. ; Ravnsbaek, Dorthe B. ; Filinchuk, Yaroslav ; Vang, Ronnie T. ; Cerenius, Yngve LU ; Besenbacher, Flemming ; Jorgensen, Jens-Erik ; Jakobsen, Hans Jorgen and Jensen, Torben R.
- organization
- publishing date
- 2009
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Chemistry of Materials
- volume
- 21
- issue
- 24
- pages
- 5772 - 5782
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- wos:000272597500011
- scopus:72949113692
- ISSN
- 0897-4756
- DOI
- 10.1021/cm902013k
- language
- English
- LU publication?
- yes
- id
- 65933323-313f-4162-885c-3ebfb701e906 (old id 1532752)
- date added to LUP
- 2016-04-01 12:18:47
- date last changed
- 2022-03-21 02:22:59
@article{65933323-313f-4162-885c-3ebfb701e906,
abstract = {{A Surprisingly high degree of structural and compositional dynamics is observed in the system LiBH4-LiCl as a function of temperature and time. Rietveld refinement of synchrotron radiation powder X-ray diffraction (SR-PXD) data reveals that Cl- readily substitutes for BH4- in the Structure of LiBH4. Prolonged heating a sample of LiBH4-LiCl (1:1 molar ratio) above the phase transition temperature and below the melting point (108 < T < 275 degrees C) can produce highly chloride substituted hexagonal lithium borohydride, h-Li(BH4)(l-x)Cl-x, e.g., x similar to 0.42, after heating from room temperature (RT) to 224 degrees C at 2.5 degrees C/min. LiCl has a higher solubility in h-LiBH4 its compared to orthorhombic lithium borohydride, o-LiBH4, which is illustrated by a LiBH4-LiCl (1:1) sample equilibrated at 245 degrees C for 24 days and left at RT for another 13 months. Rietveld refinement reveals that this sample contains o-Li(BH4)(0.91)Cl-0.09 and LiCl. This illustrates a significantly faster dissolution of LiCl in h-LiBH4 its compared to a slower segregation of LiCl from o-LiBH4, which is also demonstrated by in situ SR-PXD from three cycles of heating and cooling of the same Li(BH4)(0.91)Cl-0.09 sample. The substitution of the smaller Cl- for the larger BH4- ion is clearly observed as a reduction in the unit cell volume as a function of time and temperature. A significant stabilization of h-LiBH4 is found to depend on the degree of anion substitution. Variable temperature solid-state magic-angle spinning (MAS) Li-7 and B-13 NMR experiments oil pure LiBH4 show an increase in full width at half maximum (fwhm) when approaching the phase transition from o- to h-LiBH4, which indicates an increase of the relaxation rate (i.e. T-2 decreases). A less pronounced effect is observed for ion-substituted Li(BH4)(1-x)Cl-x, 0.09 < x < 0.42. The MAS NMR experiments also demonstrate a higher degree of motion in the hexagonal phase, i.e., fwhm is reduced by more than a Factor of 10 at the o- to h-LiBH4 phase transition.}},
author = {{Arnbjerg, Lene M. and Ravnsbaek, Dorthe B. and Filinchuk, Yaroslav and Vang, Ronnie T. and Cerenius, Yngve and Besenbacher, Flemming and Jorgensen, Jens-Erik and Jakobsen, Hans Jorgen and Jensen, Torben R.}},
issn = {{0897-4756}},
language = {{eng}},
number = {{24}},
pages = {{5772--5782}},
publisher = {{The American Chemical Society (ACS)}},
series = {{Chemistry of Materials}},
title = {{Structure and Dynamics for LiBH4-LiCl Solid Solutions}},
url = {{http://dx.doi.org/10.1021/cm902013k}},
doi = {{10.1021/cm902013k}},
volume = {{21}},
year = {{2009}},
}