Syntheses and Crystal Structures of the Lanthanum Titanium Oxyselenides La

Journal Article · Thu Mar 01 04:00:00 EST 2001 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.2000.9060· OSTI ID:784069

Tougait, Olivier; Ibers, James A

The new compounds La{sub 4}Ti{sub 2}O{sub 4}Se{sub 5} and La{sub 6}Ti{sub 3}O{sub 5}Se{sub 9} have been obtained from stoichiometric reactions of La, Ti, TiO{sub 2}, and Se in fused-silica tubes at 1223 K. Potassium halide fluxes were used to promote the crystallization. The compounds have been characterized by single-crystal X-ray diffraction methods. La{sub 4}Ti{sub 2}O{sub 4}Se{sub 5} crystallizes in the orthorhombic space group Cmcm with eight formula units in a cell at 153 K of dimensions a=3.9695(4) {angstrom}, b=33.115(3) {angstrom}, c=18.6380(18) {angstrom}. The five independent La atoms in the structure are found in four different coordination polyhedra, namely tricapped trigonal prism, bicapped trigonal prism, square antiprism, and 7-octahedron, whereas the three independent Ti atoms have octahedral coordination. The crystal structure comprises infinite layers that stack along the b-axis. Two adjacent layers are linked by La-Se bonds. La{sub 4}Ti{sub 2}O{sub 4}Se{sub 5} represents the first rare-earth titanium oxychalcogenide containing only Ti{sup 3+} cations. La{sub 6}Ti{sub 3}O{sub 5}Se{sub 9} crystallizes in the monoclinic space group C2/m with four formula units in a cell at 153 K of dimensions a=43.999(6) {angstrom}, b=3.9454(6) {angstrom}, c=11.1093(16) {angstrom}, {beta}=96.882(2){degree}. The six independent La atoms in the structure are found in three different coordination polyhedra, namely tricapped trigonal prism, bicapped trigonal prism, and 7-octahedron. The four independent Ti atoms have octahedral coordination. The crystal structure comprises infinite condensed layers of composition {sub {infinity}}{sup 2}[La{sub 2}Ti{sub 1}O{sub 2}Se{sub 3}] that stack successively with extended slabs of composition {sub {infinity}}{sup 2}[La{sub 4}Ti{sub 2}O{sub 3}Se{sub 6}] along the a-axis. La{sub 6}Ti{sub 3}O{sub 5}Se{sub 9} is a mixed-valence compound in which two-thirds of the Ti cations are Ti{sup 3+} and one-third are Ti{sup 4+}.

• Research Organization: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois (US)
• Sponsoring Organization: U. S. National Science Foundation (US)
• OSTI ID: 784069
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 157; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ATOMS
CATIONS
CHEMICAL PREPARATION
CRYSTAL STRUCTURE
CRYSTALLIZATION
DIMENSIONS
EXPERIMENTAL DATA
HALIDES
LANTHANUM
LANTHANUM COMPOUNDS
LATTICE PARAMETERS
MONOCLINIC LATTICES
ORTHORHOMBIC LATTICES
OXYSELENIDES
POTASSIUM
SPACE GROUPS
TITANIUM
TITANIUM COMPOUNDS
VALENCE
X-RAY DIFFRACTION