Structural studies on W{sup 6+} and Nd{sup 3+} substituted La{sub 2}Mo{sub 2}O{sub 9} materials

Journal Article · Sun Jan 15 04:00:00 EST 2006 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2005.10.017· OSTI ID:20784859

Marrero-Lopez, David ^[1]; Canales-Vazquez, Jesus ^[2]; Wuzong, Zhou ^[3]; Irvine, John T.S. ^[3]; Nunez, Pedro ^[1]

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1. Departamento de Quimica Inorganica, Universidad de La Laguna, E38200 La Laguna, Tenerife, Canary Islands (Spain)
2. Instituto de Ciencia de Materiales de Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain)
3. School of Chemistry, Purdie Building, University of St Andrews, St Andrews, Fife KY16 9ST (United Kingdom)

The structure of a series of new ionic conductors based in lanthanum molybdate (La{sub 2}Mo{sub 2}O{sub 9}) has been investigated using transmission electron microscopy (TEM), high-resolution X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The superstructure 2a{sub c}x3a{sub c}x4a{sub c} of the low temperature {alpha}-polymorph relative to the {beta}-polymorph was confirmed by HRTEM imaging and electron diffraction. Furthermore, the effects of partial cation substitution in the La{sub 2-x}Nd{sub x}Mo{sub 2}O{sub 9} and La{sub 2}Mo{sub 2-y}W{sub y}O{sub 9} series have been also evaluated in the search of new clues to understand the structure and stabilisation of the high temperature and better conductor {beta}-polymorph. The thermal analysis studies show that Nd-substitution does not stabilise completely the {beta}-polymorph at room temperature, although no superstructure ordering was observed by both XRD and HRTEM. On the other hand, W-substitution stabilises the cubic {beta}-polymorph for y>0.25, although, electron diffraction indicates a slight distortion from the cubic symmetry for low W-content. This distortion disappears as the W content increases and the Rietveld refinements gradually render better results.

• OSTI ID: 20784859
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 179; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CALORIMETRY
ELECTRON DIFFRACTION
LANTHANUM COMPOUNDS
MOLYBDATES
NEODYMIUM IONS
PHASE TRANSFORMATIONS
TEMPERATURE RANGE 0273-0400 K
THERMAL ANALYSIS
TRANSMISSION ELECTRON MICROSCOPY
TUNGSTEN IONS
X-RAY DIFFRACTION