Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Döbelin, N. Articles by Armbruster, T. Search for Related Content GeoRef GeoRef Citation

Stepwise dehydration of Sr-exchanged heulandite: A single-crystal X-ray study

Laboratorium für chemische und mineralogische Kristallographie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland

Correspondence: ^* E-mail: ndoebelin{at}gmx.ch

A Sr-exchanged heulandite crystal of composition Sr_4.35Ca_0.13(Al_8.96Si_27.04O₇₂)·26H₂O was used for stepwise dehydration experiments. The crystal was heated for approximately 12 h from room temperature to 250 °C in steps of 50 °C using an airflow-heater device. For single-crystal X-ray data collection the crystal was quenched to –173 °C with liquid-N₂ on the diffractometer. Due to pronounced Sr order deviating from the topological symmetry C2/m, the structure was refined in space group Cm for each dehydration state. The initial H₂O content of 26 molecules per formula unit (pfu) at room temperature decreased to 17 molecules pfu after heating at 250 °C. Heating to 270 °C mechanically destroyed the crystal and a completely dehydrated state could not be studied. The loss of H₂O and accompanying migration of Sr caused a change of cell parameters: a and c slightly decreased, b decreased, and ß remained invariant, leading to a reduction of the cell volume. As Sr loses H₂O upon dehydration, it moves toward the C rings and forms stronger bonds to the tetrahedral framework. With increasing dehydration the A and B ring become slightly compressed and elongated. Initially highly populated Sr sites split into less populated sites caused by the loss of surrounding H₂O molecules.

This article has been cited by other articles:

				D. Moraetis, G. E. Christidis, and V. Perdikatsis Ion exchange equilibrium and structural changes in clinoptilolite irradiated with {beta}- and {gamma}-radiation. Part II: divalent cations European Journal of Mineralogy, August 1, 2008; 20(4): 603 - 620. [Abstract] [Full Text] [PDF]