Three-dimensional/one-dimensional transition in the Cs sup + sublattice of the mixed valence CsTi sub 8 O sub 16 hollandite: Structures at 297 and 673 K

Journal Article · Wed May 01 04:00:00 EDT 1991 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1016/0022-4596(91)90245-D· OSTI ID:7038974

Fanchon, E; Hodeau, J L; Vicat, J; Watts, J A ^[1]

---

1. National de la Recherche Scientifique, Grenoble (France)

The mixed valence compound Cs{sub x}Ti{sub 8}O{sub 16} has been studied by X-ray and electron diffraction. It was found to belong to the hollandite structural family, with a superstructure made of sharp peaks indicating a three-dimensional long range order of Cs cations at room temperature. Heating under the electron beam of a microscope induced a phase transition in which superstructure reflections transformed to a diffuse plane perpendicular to the tunnel direction of the hollandite structure. This was confirmed by a series of X-ray precession photographs taken at several temperatures: the transition temperature is about 593 K and the transition is reversible. X-ray structure analyses have been performed below the transition (at T=297 K) and above it (at T=673K) and are reported in this paper. The space group of the high temperature phase is I4/m, with a=10.317(7){angstrom}, c=2.980(1){angstrom}. The superstructure at room temperature can be indexed in a supercell involving the multiplication of all three basic axes. The space group is I4{sub 1}/a, with a=14.524(11){angstrom}, c=5.936(2){angstrom}. At room temperature the two independent titanium sites have almost the same size, and the 3d electron is probably delocalized in accordance with the observation that Cs{sub x}Ti{sub 8}O{sub 16} is a semiconductor. The phase transition is explained by the loss of lateral correlation among tunnels. No electric phenomenon in the framework seems to be at the origin of the transition, which appears to be a purely ionic phenomenon.

• OSTI ID: 7038974
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 92:1; ISSN 0022-4596; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALI METAL COMPOUNDS
CESIUM COMPOUNDS
CHALCOGENIDES
CHARGE STATE
COHERENT SCATTERING
CRYSTAL STRUCTURE
DATA
DIFFRACTION
ELECTRON DIFFRACTION
EXPERIMENTAL DATA
HOLLANDITE
INFORMATION
LATTICE PARAMETERS
MATERIALS
MINERALS
NUMERICAL DATA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SCATTERING
SEMICONDUCTOR MATERIALS
TEMPERATURE EFFECTS
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION