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A novel high-temperature commensurate superstructure in a natural bariopyrochlore: A structural study by means of a multiphase crystal structure refinement
- Source :
-
Journal of Solid State Chemistry . Mar2006, Vol. 179 Issue 3, p729-738. 10p. - Publication Year :
- 2006
-
Abstract
- Abstract: Additional X-ray diffraction effects yielding an eightfold commensurate superstructure of the ideal pyrochlore structure were observed after annealing at 873K of a thallium-doped bariopyrochlore single crystal. Electron diffraction indicated the coexistence of two cubic phases, the pyrochlore structure and a new F-centred, cubic phase. The superstructure was solved and refined in the space group . The two phases were combined together and refined as independently diffracting to . The resulting unit-cell content is (A,□)20Nb16Ti2O53 , with A=Ba, Tl, Ce, Th. For some atomic positions of the superstructure, third- and fourth-order anharmonic ADP''s were used to account for the specific density shape having a continuous character as typical for ionic conductors. There are three distinct clusters in the superstructure, leading to a new structure type no longer strictly of pyrochlore-structure type. [Copyright &y& Elsevier]
- Subjects :
- *THALLIUM halide crystals
*CRYSTALLOGRAPHY
*X-ray diffraction
*ELECTRON diffraction
Subjects
Details
- Language :
- English
- ISSN :
- 00224596
- Volume :
- 179
- Issue :
- 3
- Database :
- Academic Search Index
- Journal :
- Journal of Solid State Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 19861945
- Full Text :
- https://doi.org/10.1016/j.jssc.2005.11.031