The intermediate phase of strontium chromate aluminate sodalite
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D. M. Többens
Abstract
At high temperatures yellow strontium chromate aluminate sodalite Sr8[Al12O24](CrO4)2 has cubic symmetry with orientational disorder of the CrO42--ions within the sodalite cages. The existence of two phase transitions at 299 K and 289 K, which result in superstructures of tetragonal and orthorhombic symmetry, respectively, is well known. The structure of the orthorhombic low-temperature phase has been solved recently. In this work we discuss the crystal structure of the intermediate phase and its determination from neutron and x-ray powder diffraction data. The structure of this phase shows only very small distortions of the framework of AlO4-tetrahedra. The CrO4-tetrahedra within the sodalite cages are partially ordered. The observed distribution of their orientations can be described as a combination of those of the low- and the high-temperature phase. 27Al-MAS-NMR spectra reveal the dynamic nature of the structure.
© 2001 Oldenbourg Wissenschaftsverlag GmbH
Artikel in diesem Heft
- Thermal expansion of decagonal Al70.7Co13.3Ni16.0 in the temperature range 15–300 K
- The intermediate phase of strontium chromate aluminate sodalite
- Crystal structure and elastic properties of betaine fumarate and of betaine maleate, two isomers of ((CH3)3NCH2COOH . OOC(CH)2COOH
- Synthesis, electronic and crystal structure of a new organic semiconductor tetramethyltetrathiafulvalene-trinitroresorcinol (2:1), (TMTTF)2(C6H2N3O8)
- Synthesis and crystal structure determination of 6-phenyl-5-phenylsulfonyl-1,2,3,4-tetrahydropyrimidine-2-thione from neutron powder diffraction data
- A contribution to the crystal chemistry of DL-malates
- Absorption correction for crystal-environment attachments from direction cosines
- Book Review
Artikel in diesem Heft
- Thermal expansion of decagonal Al70.7Co13.3Ni16.0 in the temperature range 15–300 K
- The intermediate phase of strontium chromate aluminate sodalite
- Crystal structure and elastic properties of betaine fumarate and of betaine maleate, two isomers of ((CH3)3NCH2COOH . OOC(CH)2COOH
- Synthesis, electronic and crystal structure of a new organic semiconductor tetramethyltetrathiafulvalene-trinitroresorcinol (2:1), (TMTTF)2(C6H2N3O8)
- Synthesis and crystal structure determination of 6-phenyl-5-phenylsulfonyl-1,2,3,4-tetrahydropyrimidine-2-thione from neutron powder diffraction data
- A contribution to the crystal chemistry of DL-malates
- Absorption correction for crystal-environment attachments from direction cosines
- Book Review
