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Transmission electron microscopic study of new, regular, mixed-layer structures in calcium-rare-earth fluorocorbonote minerals

Published online by Cambridge University Press:  05 July 2018

Wu Xiuling ,
Meng Dawei ,
Pan Zhaolu ,
Yang Guangming  and
Li Douxing
Wu Xiuling
Affiliation:
Department of Physics, China University of Geosciences, Wuhan 430074, P.R. China
Meng Dawei
Affiliation:
Department of Physics, China University of Geosciences, Wuhan 430074, P.R. China
Pan Zhaolu
Affiliation:
Department of Physics, China University of Geosciences, Wuhan 430074, P.R. China
Yang Guangming
Affiliation:
Department of Physics, China University of Geosciences, Wuhan 430074, P.R. China
Li Douxing
Affiliation:
Laboratory of Atomic Imaging of Solids, Institute of Metal Research, Academia Sinica, Shenyang 110015, P.R. China
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Abstract

Structures of calcium-rare-earth (Ca-RE) fluorocarbonate minerals from southwest China have been investigated using selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). They are described as combinations of layers of bastnäsite-(Ce), CeFCO3 (B layers), and synchysite-(Ce), CeFCO3·CaCO3 (S layers) (Donnay and Donnay, 1953). We report here the discovery of six new, regular, mixed-layer structures in parisite-(Ce) observed using SAED and HRTEM. The symmetry, cell parameters, chemical formulae and stacking of the structural unit layers, etc., were determined for each. The regular, mixed-layer structures are formed by stacking unit layers of bastnäsite-(Ce) and synchysite-(Ce) in varying proportions along the c axis. HRTEM shows that there are different distribution modes for the Ce-F ion layers, the CO3 ion groups between the Ce-F ion layers and the CO3 ion groups between the Ce-F and Ca ion layers. The minerals may be regarded as polymorphs with the same chemical composition and the same spacing of the unit layers, but different arrangements of ion layers in the structural unit layers and different stacking sequences of the structural unit layers.

Keywords

Ca-RE fluorocarbonate mineralmixed-layer structurehigh-resolution transmission electron microscopy
Type
Research Article
Information
Mineralogical Magazine , Volume 62 , Issue 1 , February 1998 , pp. 55 - 64
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1998

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References

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