Comparative Crystal Chemistry of Rare Earth Minerals
来源期刊：Journal of Rare Earths1992年第2期
论文作者：杨主明 潘兆橹 张建洪
文章页码：81 - 87
摘 要：<正> Polyhedral analysis is used to study the geometrical limits of the crystal structure on isomorphic substitutionof rare earths.The rare earth sites in the structure may be distinguished into six groups on the basis of meanionic radii of the substituting cations in each rare earth site:Y,Y+Ca,REE,REE+Ca,Ce+Ca,Ce.The calcula-tion of volumes of 70 rare earth polyhedra indicates that the polyhedral volumes of the heavy rare earth are in arange of 13×10-3～28×10-3 nm3,the volumes of light rare earth polyhedra are in 20×10-3～40×10-3 nm3,and the polyhedral sizes suitable to isomorphic substitution of all REE are about 21×10-3～29×10-3 nm3.Thesize of REE polyhedra depends on mean ionic radii in REE sites,coordination number and linkage of polyhedra.In structures where exist two kinds of polyhedra,with the change of composition in REE site,both REEpolyhedron and anion group polyhedron tend to be more distorted,leading to the change of structural symmetry.The contrary distortion tendencies of both polyhedra favours the stability of the structure.The phenomena maybe interpreted by the potential energy distribution or the potential energy compensating mechanism of thecrystal.
杨主明，潘兆橹，张建洪
摘 要：<正> Polyhedral analysis is used to study the geometrical limits of the crystal structure on isomorphic substitutionof rare earths.The rare earth sites in the structure may be distinguished into six groups on the basis of meanionic radii of the substituting cations in each rare earth site:Y,Y+Ca,REE,REE+Ca,Ce+Ca,Ce.The calcula-tion of volumes of 70 rare earth polyhedra indicates that the polyhedral volumes of the heavy rare earth are in arange of 13×10-3～28×10-3 nm3,the volumes of light rare earth polyhedra are in 20×10-3～40×10-3 nm3,and the polyhedral sizes suitable to isomorphic substitution of all REE are about 21×10-3～29×10-3 nm3.Thesize of REE polyhedra depends on mean ionic radii in REE sites,coordination number and linkage of polyhedra.In structures where exist two kinds of polyhedra,with the change of composition in REE site,both REEpolyhedron and anion group polyhedron tend to be more distorted,leading to the change of structural symmetry.The contrary distortion tendencies of both polyhedra favours the stability of the structure.The phenomena maybe interpreted by the potential energy distribution or the potential energy compensating mechanism of thecrystal.
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