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An X-ray diffraction and MAS NMR study of the thermal expansion properties of calcined siliceous ferrierite

Bull, I.; Lightfoot, P.; Villaescusa, L.A.; Bull, L.M.; Gover, R.K.B.; Evans, J.S.O.; Morris, R.E.

Authors

I. Bull

P. Lightfoot

L.A. Villaescusa

L.M. Bull

R.K.B. Gover

R.E. Morris



Abstract

Powder and single-crystal X-ray diffraction, combined with MAS NMR measurements, has been used to study the thermal expansion of siliceous zeolite ferrierite as it approaches a second-order displacive phase transition from a low-symmetry (Pnnm) to a high-symmetry (Immm) structure. Below the transition temperature, ferrierite exhibits positive thermal expansivity. However, above the transition temperature a significant change in thermal behavior is seen, and ferrierite becomes a negative thermal expansion material. Accurate variable-temperature single-crystal X-ray diffraction measurements confirm the transition temperature and allow the changes in average atomic position to be followed with temperature. The results from the single-crystal X-ray diffraction study can be correlated with Si-29 MAS NMR chemical shifts for the low-temperature phase. At low temperatures the results show that the positive thermal expansivity is driven by an overall increase in Si-Si distances related to an increase in Si-O-Si bond angles. However, in the high-temperature phase the Si-O-Si angles are approximately invariant with temperature, and the negative thermal expansion in this case is caused by transverse vibrations of the Si-O-Si units.

Citation

Bull, I., Lightfoot, P., Villaescusa, L., Bull, L., Gover, R., Evans, J., & Morris, R. (2003). An X-ray diffraction and MAS NMR study of the thermal expansion properties of calcined siliceous ferrierite. Journal of the American Chemical Society, 125(14), 4342-4349

Journal Article Type Article
Publication Date 2003-04
Journal Journal of the American Chemical Society
Print ISSN 0002-7863
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 125
Issue 14
Pages 4342-4349