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Thermally induced phase transitions of barium oxalates

Christensen, Axel Norlund; Arnbjerg, Lene M.; DiMasi, Elaine; Cerenius, Yngve LU ; Hauback, Bjorn C. and Jensen, Torben R. (2011) In Solid State Sciences 13(7). p.1407-1413
Abstract
The thermal decomposition of BaC2O4 center dot 3.5H(2)O and BaC2O4 center dot 0.5H(2)O was investigated using in situ synchrotron X-ray and neutron powder diffraction. The decomposition routes for the barium oxalate hydrates were observed to depend on the applied heating rate. Thermal decomposition of BaC2O4 center dot 0.5H(2)O showed transformation to alpha-BaC2O4 and to beta-BaC2O4 prior to the formation of BaCO3. The decomposition of BaC2O4 center dot 3.5H(2)O showed formation of BaC2O4 center dot 0.5H(2)O at 58 degrees C and the hemi hydrate transforms to alpha-BaC2O4 at 187 degrees C using a relatively fast heating rate of 6.25 degrees C/min. The phase transitions were more complicated using lower heating rate, which also reveal... (More)
The thermal decomposition of BaC2O4 center dot 3.5H(2)O and BaC2O4 center dot 0.5H(2)O was investigated using in situ synchrotron X-ray and neutron powder diffraction. The decomposition routes for the barium oxalate hydrates were observed to depend on the applied heating rate. Thermal decomposition of BaC2O4 center dot 0.5H(2)O showed transformation to alpha-BaC2O4 and to beta-BaC2O4 prior to the formation of BaCO3. The decomposition of BaC2O4 center dot 3.5H(2)O showed formation of BaC2O4 center dot 0.5H(2)O at 58 degrees C and the hemi hydrate transforms to alpha-BaC2O4 at 187 degrees C using a relatively fast heating rate of 6.25 degrees C/min. The phase transitions were more complicated using lower heating rate, which also reveal formation of beta-BaC2O4 coexisting with alpha-BaC2O4 along with an unidentified compound. Heating alpha- and beta-BaC2O4 to higher temperatures (T > 400 degrees C) produced BaCO3. A sample of alpha-BaC2O4 was prepared in situ by thermal decomposition of BaC2O4 center dot 3.5H(2)O on a powder neutron diffractometer. The neutron diffraction data has broad diffraction peaks due to small crystallite sizes and overlapping Bragg reflections. [A structural model for alpha-BaC2O4 was derived from the neutron pattern, triclinic, space group P-1, a = 5.127(7), b = 8.905(12), c = 9.068(12) angstrom, alpha = 82.74(1), beta = 99.46(2), gamma = 100.10(1)degrees measured at T= 300 degrees C. The average Ba-O distances are 2.84(3) angstrom and 2.66(3) angstrom for Ba 1 and Ba2 respectively, C-O atom distances in the oxalate ions were found in the range 1.25(3)-1.26(4) angstrom, and C-C distances were 1.60(1)-1.61(1) angstrom]. (C) 2011 Elsevier Masson SAS. All rights reserved. (Less)
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Contribution to journal
publication status
published
subject
keywords
Synchrotron X-ray powder diffraction, Neutron ppwder diffraction, Structure of alpha-BaC2O4, Thermal transformation of barium oxalates, hydrates
in
Solid State Sciences
volume
13
issue
7
pages
1407 - 1413
publisher
Editions scientifiques Elsevier
external identifiers
  • wos:000293425000008
  • scopus:79959740094
ISSN
1873-3085
DOI
10.1016/j.solidstatesciences.2011.04.013
language
English
LU publication?
yes
id
fbee24bb-d276-4b3f-90a1-3918f4bf0660 (old id 2065293)
date added to LUP
2011-08-29 17:34:08
date last changed
2017-01-01 03:24:12
@article{fbee24bb-d276-4b3f-90a1-3918f4bf0660,
  abstract     = {The thermal decomposition of BaC2O4 center dot 3.5H(2)O and BaC2O4 center dot 0.5H(2)O was investigated using in situ synchrotron X-ray and neutron powder diffraction. The decomposition routes for the barium oxalate hydrates were observed to depend on the applied heating rate. Thermal decomposition of BaC2O4 center dot 0.5H(2)O showed transformation to alpha-BaC2O4 and to beta-BaC2O4 prior to the formation of BaCO3. The decomposition of BaC2O4 center dot 3.5H(2)O showed formation of BaC2O4 center dot 0.5H(2)O at 58 degrees C and the hemi hydrate transforms to alpha-BaC2O4 at 187 degrees C using a relatively fast heating rate of 6.25 degrees C/min. The phase transitions were more complicated using lower heating rate, which also reveal formation of beta-BaC2O4 coexisting with alpha-BaC2O4 along with an unidentified compound. Heating alpha- and beta-BaC2O4 to higher temperatures (T > 400 degrees C) produced BaCO3. A sample of alpha-BaC2O4 was prepared in situ by thermal decomposition of BaC2O4 center dot 3.5H(2)O on a powder neutron diffractometer. The neutron diffraction data has broad diffraction peaks due to small crystallite sizes and overlapping Bragg reflections. [A structural model for alpha-BaC2O4 was derived from the neutron pattern, triclinic, space group P-1, a = 5.127(7), b = 8.905(12), c = 9.068(12) angstrom, alpha = 82.74(1), beta = 99.46(2), gamma = 100.10(1)degrees measured at T= 300 degrees C. The average Ba-O distances are 2.84(3) angstrom and 2.66(3) angstrom for Ba 1 and Ba2 respectively, C-O atom distances in the oxalate ions were found in the range 1.25(3)-1.26(4) angstrom, and C-C distances were 1.60(1)-1.61(1) angstrom]. (C) 2011 Elsevier Masson SAS. All rights reserved.},
  author       = {Christensen, Axel Norlund and Arnbjerg, Lene M. and DiMasi, Elaine and Cerenius, Yngve and Hauback, Bjorn C. and Jensen, Torben R.},
  issn         = {1873-3085},
  keyword      = {Synchrotron X-ray powder diffraction,Neutron ppwder diffraction,Structure of alpha-BaC2O4,Thermal transformation of barium oxalates,hydrates},
  language     = {eng},
  number       = {7},
  pages        = {1407--1413},
  publisher    = {Editions scientifiques Elsevier},
  series       = {Solid State Sciences},
  title        = {Thermally induced phase transitions of barium oxalates},
  url          = {http://dx.doi.org/10.1016/j.solidstatesciences.2011.04.013},
  volume       = {13},
  year         = {2011},
}