The microstructural features of clacium rare earth(Ca RE) fluorocarbonate minerals from Southwest China were studied by using selected area electron diffraction(SAED) and high resolution transmission electron micros...The microstructural features of clacium rare earth(Ca RE) fluorocarbonate minerals from Southwest China were studied by using selected area electron diffraction(SAED) and high resolution transmission electron microscopy(HRTEM). Three new regularly mixed layer structures of B 8S 6 type with long period and different stacking sequence, i.e. B 8S 6 Ⅰ, B 8S 6 Ⅱ, and B 8S 6 Ⅲ, were found in the derived polycrystal of parisite, in which their structural symmetry, cell parameters, chemical formulas of crystal and stacking models of structural unit layer, etc. were determined. The results of this study also show that these new regularly mixed layer structrues were formed by order stacking unit layer of bastnaesite(B) and synchisite(S) in varying proportion along c axis. The observation under HRTEM reveals that in the three new regularly mixed layer structures there are different distribution modes of Ce F ion layers, CO 2- 3 ion groups between the Ce F ion layers, and CO 2- 3 ion groups between Ce F and Ca 2+ ion layers, and there are some heterogeneous textures, such as disorder interlayer and stacking fault. It further proves the complexity of the crystal structure of the Ca RE fluorocarbonate minerals.展开更多
The domain structures in calcium-cerium fluorocarbonate mineral series from a rare earth mineral deposit within an aegirine alkali granite massif in Mianning County, Sichuan Province, China, were studied by means of t...The domain structures in calcium-cerium fluorocarbonate mineral series from a rare earth mineral deposit within an aegirine alkali granite massif in Mianning County, Sichuan Province, China, were studied by means of transmission electron microscopy. Many categories of domain structures in this mineral series were observed and investigated, including the microtwin domains of parisite-6R(2) and B2S-6R, the antiphase domains of B2S-2H. The results show that the antiphase domains which are faults along crystal plane (0001) are formed by the displacement of crystal lattice in c * direction and the displacement is 0.471 nm. A new polytype (B4S2-3R) of regular mixed-layer structure with B4S2 type is found in the domain region of mixed-layer structure.展开更多
The microstructural characteristics of syntactic polycrystal in the calcium rare earth fluorocarbonate minerals from Southwest China have been studied by means of selected area electron diffraction and high resolutio...The microstructural characteristics of syntactic polycrystal in the calcium rare earth fluorocarbonate minerals from Southwest China have been studied by means of selected area electron diffraction and high resolution electron microscopy(HREM). The complication of the heterogeneous fabric of the minerals have been revealed by HREM. The results show that the crystal structure of the minerals was formed by a disorder stacking of the unit layers of bast naesite and synchisite in the calcium rare earth fluorocarbonate minerals along c direction. The stacking fault and other crystal defects in the syntactic polycrystal have been discussed.展开更多
文摘The microstructural features of clacium rare earth(Ca RE) fluorocarbonate minerals from Southwest China were studied by using selected area electron diffraction(SAED) and high resolution transmission electron microscopy(HRTEM). Three new regularly mixed layer structures of B 8S 6 type with long period and different stacking sequence, i.e. B 8S 6 Ⅰ, B 8S 6 Ⅱ, and B 8S 6 Ⅲ, were found in the derived polycrystal of parisite, in which their structural symmetry, cell parameters, chemical formulas of crystal and stacking models of structural unit layer, etc. were determined. The results of this study also show that these new regularly mixed layer structrues were formed by order stacking unit layer of bastnaesite(B) and synchisite(S) in varying proportion along c axis. The observation under HRTEM reveals that in the three new regularly mixed layer structures there are different distribution modes of Ce F ion layers, CO 2- 3 ion groups between the Ce F ion layers, and CO 2- 3 ion groups between Ce F and Ca 2+ ion layers, and there are some heterogeneous textures, such as disorder interlayer and stacking fault. It further proves the complexity of the crystal structure of the Ca RE fluorocarbonate minerals.
文摘The domain structures in calcium-cerium fluorocarbonate mineral series from a rare earth mineral deposit within an aegirine alkali granite massif in Mianning County, Sichuan Province, China, were studied by means of transmission electron microscopy. Many categories of domain structures in this mineral series were observed and investigated, including the microtwin domains of parisite-6R(2) and B2S-6R, the antiphase domains of B2S-2H. The results show that the antiphase domains which are faults along crystal plane (0001) are formed by the displacement of crystal lattice in c * direction and the displacement is 0.471 nm. A new polytype (B4S2-3R) of regular mixed-layer structure with B4S2 type is found in the domain region of mixed-layer structure.
文摘The microstructural characteristics of syntactic polycrystal in the calcium rare earth fluorocarbonate minerals from Southwest China have been studied by means of selected area electron diffraction and high resolution electron microscopy(HREM). The complication of the heterogeneous fabric of the minerals have been revealed by HREM. The results show that the crystal structure of the minerals was formed by a disorder stacking of the unit layers of bast naesite and synchisite in the calcium rare earth fluorocarbonate minerals along c direction. The stacking fault and other crystal defects in the syntactic polycrystal have been discussed.
