Equilibrium relations in the system TiO{sub 2}/V{sub 2}O{sub 5}/P{sub 2}O{sub 5} and crystal structure of a NASICON-related vanadyl(V) titanium(IV) phosphate

Journal Article · Sat Dec 15 04:00:00 EST 2012 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2012.07.022· OSTI ID:22149983

Titlbach, Sven; Hoffbauer, Wilfried ^[1]; Glaum, Robert ^[1]

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1. Institut fuer Anorganische Chemie der Universitaet Bonn, Gerhard-Domagk-Str. 1, D-53121 Bonn (Germany)

Vanadyl(V)-titanium-orthophosphate (V{sup V}O)Ti{sup IV}{sub 6}(PO{sub 4}){sub 9} is formed by solid state reactions in the temperature range 525{<=}{theta}{<=}780 Degree-Sign C. At higher temperature decomposition into V{sub 2}O{sub 5} and the hitherto unknown solid solution Ti(P{sub 1-x}V{sub x}){sub 2}O{sub 7} (0{<=}x{<=}0.23; 0.30{<=}x{<=}0.43) is observed. The process of phase formation has been monitored by MAS-NMR ({sup 31}P, {sup 51}V) spectroscopy. Equilibrium phase relations in the quaternary system TiO{sub 2}/VO{sub 2.5}/PO{sub 2.5} have been determined. A structure analysis from X-ray single-crystal data (P6{sub 3}/m (No. 176), Z=2; a=8.4438(3) A, c=22.215(1) A, 14 independent atoms, 87 variables, 2066 unique reflections, R1=0.032, wR2=0.084) shows the relationship of (V{sup V}O)Ti{sup IV}{sub 6}(PO{sub 4}){sub 9} to the NASICON structure family. In marked contrast to the other members of this family [Ti{sup IV}{sub 2}O{sub 9}] double-octahedra and strongly distorted tetrahedral [(V{sup V}=O)O{sub 3}] groups are observed besides isolated [Ti{sup IV}O{sub 6}] octahedra and phosphate tetrahedra. The structure model is in agreement with the results from MAS-NMR ({sup 31}P, {sup 51}V) spectroscopy. - Graphical abstract: (V{sup V}O)Ti{sup IV}{sub 6}(PO{sub 4}){sub 9} belongs to the NASICON structure family. Its structure contains [Ti{sup IV}{sub 2}O{sub 9}] double-octahedra and unprecedented, strongly distorted tetrahedral [(V{sup V}=O)O{sub 3}] groups, in stark contrast to other members of this family. The structure model is in agreement with the results from MAS-NMR ({sup 31}P, {sup 51}V) spectroscopy. Highlights: Black-Right-Pointing-Pointer Equilibrium relations for the subsolidus have been established for the system TiO{sub 2}/V{sub 2}O{sub 5}/P{sub 2}O{sub 5}. Black-Right-Pointing-Pointer Phase formation has been monitored by XRPD as well as by {sup 31}P- and {sup 51}-MAS-NMR. Black-Right-Pointing-Pointer A solid solution Ti(P{sub 1-x}V{sub x}){sub 2}O{sub 7} exists up to x=0.43 with a miscibility gap at 0.23{<=}x{<=}0.30. Black-Right-Pointing-Pointer The crystal structure of the new NASICON-related phosphate (V{sup V}O)Ti{sup IV}{sub 6}(PO{sub 4}){sub 9} is reported. Black-Right-Pointing-Pointer The crystal structure contains the unprecedented [(V=O)O{sub 3}] group.

• OSTI ID: 22149983
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 196; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CATALYSTS
DECOMPOSITION
HEXAGONAL LATTICES
MONOCRYSTALS
NUCLEAR MAGNETIC RESONANCE
OXIDATION
PHOSPHATES
PHOSPHORUS 31
PHOSPHORUS OXIDES
SOLID SOLUTIONS
SOLIDS
SPECTROSCOPY
TITANIUM
TITANIUM OXIDES
VANADATES
VANADIUM OXIDES
X RADIATION