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Maxim Avdeev Andrei Kholkin 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):e539-e540
The crystal structure of the low-temperature Na4Ti5O12 (tetrasodium pentatitanium dodecaoxide) phase has been solved and refined from X-ray and neutron powder diffraction data at 295 K. The structure is trigonal, space group P3, with Z = 1, although it is pseudo-centrosymmetric. The O and Na atoms form a distorted close-packed structure, where Ti atoms occupy octahedral sites. 相似文献
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Julian R. Tolchard Marie‐Laure Fontaine Tor Grande 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(4):i11-i13
Lanthanum nickel niobium trioxide has been synthesized and its structure refined for the first time. It was found to be a member of the family of technologically important `double perovskites', crystallizing in the monoclinic space group P21/n. The structure is characterized by a strong orthorhombic pseudosymmetry and a concurrent exhibition of both 1:1 B‐cation ordering and a−a−c+‐type tilting of the (Ni/Nb)O6 structural units. Trivalent lanthanum resides on the perovskite A site, which is strongly distorted owing to the tilting of the (Ni/Nb)O6 sublattice. Ordering of divalent nickel and pentavalent niobium on the B sublattice is described in terms of two twofold special positions (2c and 2d), with nickel taking almost complete occupancy of the 2d site and the 2c position being occupied by a statistical distribution of nickel and niobium. 相似文献
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The room temperature structure of perovskite CeAlO3 has been reinvestigated by X-ray powder diffraction. The Rietveld refinement has confirmed the tetragonal symmetry; but revealed a super cell, a=5.32489(6) Å and c=7.58976(10) Å, with the space group I4/mcm. In CeAlO3, the distortion from the ideal cubic perovskite is caused by the cooperative tilting of the AlO6 octahedra around the primitive cubic [001]p-axis. 相似文献
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The specific heat values of Bi4Ge3O12 and Bi4Ti3O12 single crystals have been studied using a DSC instrument in the temperature range from 323 to 1273 K. The temperature range at which the anomaly associated with transition from polarized to non-polarized phase in Bi4Ti3O12 occurred, has been estimated using the shape of the Bi4Ge3O12 heat capacity curve as a “normal” one. The heat effect and the entropy change of the transition were evaluated. 相似文献