Cametti, Georgia; Armbruster, Thomas Michael; Nagashima, Mariko (2016). Dehydration and thermal stability of elpidite: An in-situ single crystal X-ray diffraction study. Microporous and mesoporous materials, 227, pp. 81-87. Elsevier 10.1016/j.micromeso.2016.02.049
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Elpidite Na2ZrSi6O15·3H2O is a natural zirconosilicate with space group Pbcm. A sample from Mt. Saint Hilaire (Canada) was investigated between 25 and 350 °C under different humidity conditions (RH = 0% and at RH = 100%). The largest structural channels are eight- and ten-rings delimited by corner-sharing SiO4 tetrahedra and ZrO6 octahedra.
Under dry conditions, the structure started liberating water at 75 °C. At 100 °C, when it lost one H2O molecule, elpidite underwent a structural change from space group Pbcm to Cmce.
The structure continuously released water up to 225 °C until it became anhydrous. From 225 °C to 350 °C no structural changes were observed. Associated with the transition from Pbcm to Cmce symmetry, the unit-cell volume reduced by 2.7%. An additional decrease is observed up to 225 °C when the contraction reached 3.4% of the starting volume. After release of all H2O molecules, increase of temperature led to gradual expansion of the unit cell from 2940.79 (7) Å3 at 225 °C to 2947.4 (5) Å3 at 350 °C.
Supplementary ex-situ heating experiments showed that the structure was retained up to 950 °C but after heating at 1200 °C the sample melted.
Under humid conditions a dehydration-trend similar to that found under a dry N2-atmosphere was observed but the structural changes occurred at slightly higher temperatures.
Immersion of a dehydrated sample in water for 30 days led to only marginal rehydration and the Cmce symmetry was preserved.
Item Type: |
Journal Article (Original Article) |
|---|---|
Division/Institute: |
08 Faculty of Science > Institute of Geological Sciences > Mineralogy 08 Faculty of Science > Institute of Geological Sciences |
UniBE Contributor: |
Cametti, Georgia, Armbruster, Thomas Michael |
Subjects: |
500 Science > 540 Chemistry 500 Science > 550 Earth sciences & geology |
ISSN: |
1387-1811 |
Publisher: |
Elsevier |
Language: |
English |
Submitter: |
Georgia Cametti |
Date Deposited: |
07 Jun 2017 13:03 |
Last Modified: |
05 Dec 2022 15:03 |
Publisher DOI: |
10.1016/j.micromeso.2016.02.049 |
BORIS DOI: |
10.7892/boris.96214 |
URI: |
https://boris.unibe.ch/id/eprint/96214 |
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