Synchrotron Powder X-ray Diffraction Study of the Structure and Dehydration Behavior of Sepiolite

Journal Article · Mon Jan 01 04:00:00 EST 2007 · American Mineralogist

DOI:https://doi.org/10.2138/am.2007.2134· OSTI ID:930270

Post, J; Bish, D; Heaney, P

Rietveld refinements using synchrotron powder X-ray diffraction data were used to study the crystal structure and dehydration behavior of sepiolite from Durango, Mexico. The room-temperature (RT) sepiolite structure in air compares well with previous models but reveals an additional zeolitic H{sub 2}O site. The RT structure under vacuum retained only {approx}1/8 of the zeolitic H{sub 2}O and the volume decreased by 1.3%. Real-time, temperature-resolved synchrotron powder X-ray diffraction data and Rietveld refinements were used to investigate the behavior of the sepiolite structure from 300 to 925 K. Rietveld refinements revealed that most of the zeolitic H{sub 2}O is lost by {approx}390 K, accompanied by a decrease in the a and c unit-cell parameters. Above {approx}600 K the sepiolite structure folds as one-half of the crystallographically bound H{sub 2}O is lost. Rietveld refinements of the 'anhydrous' sepiolite structure reveal that, in general, unit-cell parameters a and b and volume steadily decrease with increasing temperature; there is an obvious change in slope at {approx}820 K suggesting a phase transformation coinciding with the loss of the remaining bound H{sub 2}O molecule.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 930270
• Report Number(s): BNL--80968-2008-JA
• Journal Information: American Mineralogist, Journal Name: American Mineralogist Vol. 92; ISSN AMMIAY; ISSN 0003-004X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
43 PARTICLE ACCELERATORS
AIR
AUGMENTATION
CRYSTAL STRUCTURE
DATA
DEHYDRATION
MEXICO
PHASE TRANSFORMATIONS
POWDERS
SEPIOLITE
SYNCHROTRONS
VOLUME
X-RAY DIFFRACTION
national synchrotron light source