Phase relations in Na{sub x}Cr{sub x}Ti{sub 8-x}O{sub 16} at 1350deg. C and crystal structure of hollandite-like Na{sub 2}Cr{sub 2}Ti{sub 6}O{sub 16}

Journal Article · Tue Aug 15 04:00:00 EDT 2006 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2006.05.007· OSTI ID:20905411

Michiue, Yuichi ^[1]

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1. National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

Phase relations of rutile, freudenbergite, and hollandite structures were examined in the pseudobinary system NaCrO{sub 2}-TiO{sub 2} (i.e., Na{sub x}Cr{sub x}Ti{sub 8-x}O{sub 16}) at 1350deg. C. The hollandite structure was obtained in the composition range 1.7=<x=<2.0. The symmetry of the samples at room temperature was tetragonal for x=1.7 and 1.75, and monoclinic for x=1.8 and above. Single crystals of monoclinic hollandite Na{sub 2}Cr{sub 2}Ti{sub 6}O{sub 16} were grown and the structure refinement has been carried out using an X-ray diffraction technique. The space group was I2/m and cell parameters were a=10.2385(11), b=2.9559(9), c=9.9097(11)A, and {beta}=90.545(9){sup o} with Z=1. The Na ion distribution in the tunnel was markedly deformed from that in the tetragonal form. It was suggested that Cr/Ti ratios were different between the two framework metal sites.

• OSTI ID: 20905411
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 8 Vol. 179; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHROMITES
HOLLANDITE
MONOCLINIC LATTICES
MONOCRYSTALS
PHASE TRANSFORMATIONS
RUTILE
SODIUM COMPOUNDS
SODIUM IONS
SPACE GROUPS
TEMPERATURE RANGE 0273-0400 K
TETRAGONAL LATTICES
TITANIUM OXIDES
X-RAY DIFFRACTION