The thermal dehydration process of the natural Li zeolite bikitaite has been studied in situ by synchrotron radiation powder diffraction. The temperature-resolved experiments were performed using a translating imaging plate system. Rietveld refinements were carried out on 42 powder patterns in the temperature range from room temperature to 800 degreesC. Bikitaite is stable at least up to 800 degreesC, the temperature at which the phase transition to gamma-spodumene begins. The dehydration process begins at about 200 degreesC, affecting the two water sites in a similar way, and is complete at 468 degreesC. Such a process induces only very minor structural distortions in the framework, due to the anti-rotation of the internal T-O-T hinges. In this sense, bikitaite can be defined as a flexible but non-collapsible framework, and it is the zeolite that undergoes the lowest heating-induced distortion among those studied up to now. The high thermal and structural stability suggest that anhydrous bikitaite could be used as a solid porous matrix for embedding nanosized materials in its one-dimensional channels.
Dehydration dynamics of bikitaite: Part I. In situ synchrotron powder X-ray diffraction study
CERIANI, CHIARA;FOIS, ETTORE SILVESTRO;GAMBA, ALDO;
2004-01-01
Abstract
The thermal dehydration process of the natural Li zeolite bikitaite has been studied in situ by synchrotron radiation powder diffraction. The temperature-resolved experiments were performed using a translating imaging plate system. Rietveld refinements were carried out on 42 powder patterns in the temperature range from room temperature to 800 degreesC. Bikitaite is stable at least up to 800 degreesC, the temperature at which the phase transition to gamma-spodumene begins. The dehydration process begins at about 200 degreesC, affecting the two water sites in a similar way, and is complete at 468 degreesC. Such a process induces only very minor structural distortions in the framework, due to the anti-rotation of the internal T-O-T hinges. In this sense, bikitaite can be defined as a flexible but non-collapsible framework, and it is the zeolite that undergoes the lowest heating-induced distortion among those studied up to now. The high thermal and structural stability suggest that anhydrous bikitaite could be used as a solid porous matrix for embedding nanosized materials in its one-dimensional channels.
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