The fluorite-pyrochlore transformation of Ho{sub 2-y}Nd{sub y}Zr{sub 2}O{sub 7}

Journal Article · Mon Aug 15 00:00:00 EDT 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.05.054· OSTI ID:21580186

Clements, Richard ^[1]; Hester, James R ^[1]; Ling, Chris D ^[1]; Stampfl, Anton P.J. ^[2]

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1. School of Chemistry, University of Sydney, Sydney, NSW 2006 (Australia)
2. School of Chemistry, niversity of Sydney, Sydney, NSW 2006 (Australia)

Twelve members of the Ho{sub 2-y}Nd{sub y}Zr{sub 2}O{sub 7} series, prepared using conventional solid state methods, have been characterised by neutron powder diffraction. Ho{sub 2}Zr{sub 2}O{sub 7} has a defect fluorite structure whereas Nd{sub 2}Zr{sub 2}O{sub 7} is found to adopt the ordered pyrochlore structure with the composition induced fluorite-pyrochlore transformation occurring near y=1. Rietveld analysis on the neutron data for all the compositions reveals an increase in lattice parameter as a function of y across the entire series, with a small discontinuity associated with the transformation. The neutron profile results suggest that domains of pyrochlore-type initially begin to form before crystallising into a separate phase, and therefore that anion and cation ordering processes are distinct. There is a strong correlation between the extent of disorder in the anion sublattice and the x-parameter of 48f oxygen. These results point the way to a better understanding of the stability observed in pyrochlore structures. - Graphical abstract: Neutron diffraction profiles for Nd{sub 2-y}Ho{sub y}Zr{sub 2}O{sub 7} type oxides reveal details of the transformation from the ordered pyrochlore structure (y=0) to the disordered fluorite structure (y=2). Highlights: > Structures of twelve members of the Ho{sub 2-y}Nd{sub y}Zr{sub 2}O{sub 7} series studied using neutron powder diffraction. > Domains of pyrochlore-type materials form at low doping levels. > Higher doping stabilises the pyrochlore. > Anion and cation ordering processes are distinct.

• OSTI ID: 21580186
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 8; Other Information: DOI: 10.1016/j.jssc.2011.05.054; PII: S0022-4596(11)00303-3; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANIONS
DEFECTS
FLUORITE
LATTICE PARAMETERS
NEODYMIUM COMPOUNDS
NEUTRON DIFFRACTION
NEUTRONS
OXIDES
OXYGEN
PYROCHLORE
TRANSFORMATIONS
ZIRCONATES
BARYONS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
DIFFRACTION
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
HADRONS
HALIDE MINERALS
IONS
MINERALS
NONMETALS
NUCLEONS
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
SCATTERING
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS