The structures of C-Ce2O3+δ, Ce7O12, and Ce11O20
The structures of C-Ce2O3+δ, Ce7O12, and Ce11O20
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DOI：
10.1006/jssc.1999.8403
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发表时间：
1999-11-01
影响因子：
3.3
通讯作者：
Heger, G
中科院分区：
文献类型：
--
作者：
Kümmerle, EA;Heger, G
通过对在环境温度下收集的单晶中子衍射数据进行精修，确定了具有有序氧空位分布的CeO₁.₆₈（C - Ce₂O₃ + δ）、Ce₇O₁₂和Ce₁₁O₂₀的晶体结构。CeO₁.₆₈是立方晶系，空间群为\(\overline{Ia3}\)，a = 11.111(2) Å；两个氧位置中的一个被部分占据，占据概率为37(3)%。对于Ce₇O₁₂，确认其为菱面体空间群\(\overline{R3}\)，a = 6.785(1) Å，α = 99.42(1)°。Ce₁₁O₂₀与Tb₁₁O₂₀同构，为三斜晶系空间群\(\overline{P1}\)。晶格参数为a = 6.757(3) Å，b = 10.260(5) Å，c = 6.732(3) Å，α = 90.04(4)°，β = 99.80(4)°，γ = 96.22(4)°。对于Ce₁₁O₂₀，不存在\(\frac{1}{2}[1,1,1](F)\)氧空位对，即沿[1, 1, 1](F)方向对应萤石晶格空间对角线一半的空位对。该结构中最短的空位对类型是\(\frac{1}{2}[1, 1, 1](F)\)，这在另外两个相中也存在。高温中子衍射测量表明，Ce₇O₁₂在高达1072 K时是稳定的。然后它转变为具有无序氧空位的萤石型结构。（C）1999年学术出版社。
The crystal structures of CeO1.68 (C-Ce2O3+delta), Ce7O12, and Ce11O20 with ordered oxygen vacancy distributions have been determined by refinement of single crystal neutron diffraction data collected at ambient temperature. CeO1.68 is cubic, of space group Ia (3) over bar with a = 11.111(2) Angstrom; one of the two oxygen positions is partially occupied with a probability of 37(3)%. For Ce7O12 the rhombohedral space group R (3) over bar with a 6.785(1) Angstrom, alpha = 99.42(1)degrees was confirmed. Ce11O20 is isomorphous to Tb11O20 with the triclinic space group P (1) over bar. The lattice parameters are a 6.757(3) Angstrom, b = 10.260(5) Angstrom, c = 6.732(3) Angstrom, alpha = 90.04(4)degrees, beta = 99.80(4)degrees, and gamma = 96.22(4)degrees. For Ce11O20 there are no 1/2[1,1,1](F) oxygen vacancy pairs, i.e., pairs corresponding to half of the space diagonal of the fluorite lattice along [1, 1, 1](F). The shortest vacancy pair type in that structure is 1/2[1, 1, 1](F), which is also present in the two other phases. High temperature neutron diffraction measurements showed that Ce7O12 is stable up to 1072 K. Then it transforms into a fluorite type structure with disordered oxygen vacancies. (C) 1999 Academic Press.