Synthesis, structure, and reactivity of novel lanthanum tungstates

Journal Article · Fri Jul 01 00:00:00 EDT 1994 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1994.1207· OSTI ID:7073018

Gaertner, M; Abeln, D; Pring, A; Wilde, M; Reller, A ^[1]

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1. Univ. of Hamburg (Germany)

Two new compounds, La[sub 2]W[sub 3]O[sub 12] and LaFeW[sub 3]O[sub 12], were prepared from La[sub 2]O[sub 3] and WO[sub 3] or from Fe[sub 2]O[sub 3], La[sub 2]O[sub 3], and WO[sub 3]. La[sub 2]W[sub 3]O[sub 12] has a structure which can be considered as a distorted superstructure of the scheelite structure CaWO[sub 4] in which 1/3 of the Ca sites are vacant. It is monoclinic, with space group C2/c and a = 7.873(2) [angstrom], b = 11.841(2) [angstrom], c = 11.654(2) [angstrom], and [beta] = 109.25(3)[degrees]. LaFeW[sub 3]O[sub 12] is triclinic with a = 7.569(3) [angstrom], b = 7.537(2) [angstrom], c = 32.41(2) [angstrom], [alpha] = 90.13(4)[degrees], [beta] = 94.75(3)[degrees], and [gamma] = 98.90(3)[degrees], and the structure consists of two distinct layers, one of which is a La tungstate which consists of a sheet of La in eight coordination and a sheet of WO[sub 4] tetrahedra and another which consists of a sheet of edge-sharing FeO[sub 6] octahedra sandwiched between two sheets of edge-connected WO[sub 6] octahedra. The reactivity of these compounds with H[sub 2] was investigated by TGA. La[sub 2]W[sub 3]O[sub 12] is reduced at 1100[degrees]C to yield a mixture of La[sub 2]O[sub 3] and W metal. The products of the reduction of LaFeW[sub 3]O[sub 12] were found to depend on the composition of the atmosphere. In N[sub 2] with 5% H[sub 2] the compound yields a complex mixture of La[sub x](WO[sub 3])[sub y] compounds with W and a W-Fe alloy, while in 100% H[sub 2], La[sub 2]O[sub 3], W, and the alloys Fe[sub 6]W[sub 7] or Fe[sub 2]W are formed.

• OSTI ID: 7073018
• Journal Information: Journal of Solid State Chemistry; (United States), Vol. 111:1; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
LANTHANUM TUNGSTATES
CRYSTAL STRUCTURE
CHEMICAL PREPARATION
LATTICE PARAMETERS
MONOCLINIC LATTICES
REDUCTION
THERMAL GRAVIMETRIC ANALYSIS
TRICLINIC LATTICES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
CRYSTAL LATTICES
GRAVIMETRIC ANALYSIS
LANTHANUM COMPOUNDS
QUANTITATIVE CHEMICAL ANALYSIS
RARE EARTH COMPOUNDS
SYNTHESIS
THERMAL ANALYSIS
TUNGSTATES
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
400201 - Chemical & Physicochemical Properties