Structures of ordered tungsten- or molybdenum-containing quaternary perovskite oxides

Journal Article · Sun Jan 15 04:00:00 EST 2012 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.11.007· OSTI ID:21612858

Day, Bradley E; Bley, Nicholas D; Jones, Heather R; McCullough, Ryan M ^[1]; Eng, Hank W ^[2]; Porter, Spencer H; Woodward, Patrick M ^[3]

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1. Department of Chemistry, Millikin University, 1184 W. Main Street, Decatur, IL 62522 (United States)
2. Department of Natural Sciences, San Antonio College, 1300 San Pedro Avenue, San Antonio, TX 78212 (United States)
3. Department of Chemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, OH 43210 (United States)

The room temperature crystal structures of six A{sub 2}MMoO{sub 6} and A{sub 2}MWO{sub 6} ordered double perovskites were determined from X-ray and neutron powder diffraction data. Ba{sub 2}MgWO{sub 6} and Ba{sub 2}CaMoO{sub 6} both adopt cubic symmetry (space group Fm3-bar m, tilt system a{sup 0}a{sup 0}a{sup 0}). Ba{sub 2}CaWO{sub 6} has nearly the same tolerance factor (t=0.972) as Ba{sub 2}CaMoO{sub 6} (t=0.974), yet it surprisingly crystallizes with I4/m symmetry indicative of out-of-phase rotations of the MO{sub 6} octahedra about the c-axis (a{sup 0}a{sup 0}c{sup -}). Sr{sub 2}ZnMoO{sub 6} (t=0.979) also adopts I4/m symmetry; whereas, Sr{sub 2}ZnWO{sub 6} (t=0.976) crystallizes with monoclinic symmetry (P2{sub 1}/n) with out-of-phase octahedral tilting distortions about the a- and b-axes, and in-phase tilting about the c-axis (a{sup -}a{sup -}c{sup +}). Ca{sub 2}CaWO{sub 6} (t=0.867) also has P2{sub 1}/n symmetry with large tilting distortions about all three crystallographic axes and distorted CaO{sub 6} octahedra. Analysis of 93 double perovskites and their crystal structures showed that while the type and magnitude of the octahedral tilting distortions are controlled primarily by the tolerance factor, the identity of the A-cation acts as the secondary structure directing factor. When A=Ba{sup 2+} the boundary between cubic and tetragonal symmetries falls near t=0.97, whereas when A=Sr{sup 2+} this boundary falls somewhere between t=1.018 and t=0.992. - Graphical abstract: A survey of the tolerance factor of 41 Mo/W- and 52 Nb/Ta-containing quaternary perovskites plotted as a function of the difference between the two six-coordinate M-cation ionic radii. Compounds with cubic symmetry are represented by diamonds, those with tetragonal symmetry are represented by squares, those with I2/m monoclinic symmetry are represented by Multiplication-Sign , and those with P2{sub 1}/n monoclinic symmetry are represented by triangles. White symbols represent compositions where A=Ba{sup 2+}, gray symbols represent compositions where A=Sr{sup 2+}, and black symbols represent where A=Ca{sup 2+}. The filled circle represents rhombohedral Ba{sub 2}BiTaO{sub 6} (t=0.961; space group-R3-bar ; tilt system-a{sup -}a{sup -}a{sup -}). References for the compounds included in this figure are listed in the Supporting Information File. Black-Small-Square Highlights: Black-Right-Pointing-Pointer Reports the structures of six double perovskites containing either Mo{sup 6+} or W{sup 6+}. Black-Right-Pointing-Pointer Compounds with similar tolerance factors (t) exhibited different symmetries. Black-Right-Pointing-Pointer This effect was observed in Sr{sub 2}ZnMO{sub 6} and Ba{sub 2}CaMO{sub 6} (M=Mo or W). Black-Right-Pointing-Pointer Contains a structural survey of 93 double perovskites. Black-Right-Pointing-Pointer Octahedral tilting distortions are controlled by t and the nature of the A-cation.

• OSTI ID: 21612858
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 185; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CARBON
CARBON IONS
CATIONS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
CUBIC LATTICES
DIAMONDS
DIFFRACTION
ELECTROMAGNETIC RADIATION
ELEMENTS
IONIZING RADIATIONS
IONS
METALS
MINERALS
MOLYBDENUM
MOLYBDENUM IONS
MONOCLINIC LATTICES
NEUTRON DIFFRACTION
NONMETALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PEROVSKITE
PEROVSKITES
RADIATIONS
REFRACTORY METALS
SCATTERING
SPACE GROUPS
STRONTIUM IONS
SYMMETRY GROUPS
TETRAGONAL LATTICES
TOLERANCE
TRANSITION ELEMENTS
TRIGONAL LATTICES
TUNGSTEN
TUNGSTEN IONS
X RADIATION
X-RAY DIFFRACTION