title: Anion disorder in lanthanoid zirconates Gd(2-x)Tb(x)Zr2O7.
abstract: The pyrochlore-defect fluorite order-disorder transition has been studied for a series of oxides of the type Gd(2-x)Tb(x)Zr2O7 by a combination of diffraction and spectroscopy techniques. Synchrotron X-ray diffraction data suggest an abrupt transition from the coexistence of pyrochlore and defect fluorite phases to a single defect fluorite phase with increasing Tb content. However neutron diffraction data, obtained at λ ≈ 0.497 Å for all Gd-containing samples to minimize absorption, not only provide evidence for independent ordering of the anion and cation sublattices but also suggest that the disorder transition across the pyrochlore-defect fluorite boundary of Ln2Zr2O7 is rather gradual. Such disorder was also evident in X-ray absorption measurements at the Zr L3-edge, which showed a gradual increase in the effective coordination number of the Zr from near 6-coordinate in the pyrochlore rich samples to near 7-coordinate in the Tb rich defect fluorites. These results indicate the presence of ordered domains throughout the defect fluorite region, and demonstrate the gradual nature of the order-disorder transition across the Gd(2-x)Tb(x)Zr2O7 series.
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, NSW 2006 Australia.
authors.forename: Emily
authors.initials: E
authors.lastname: Reynolds
authors.forename: Peter E R
authors.initials: PE
authors.lastname: Blanchard
authors.forename: Brendan J
authors.initials: BJ
authors.lastname: Kennedy
authors.forename: Chris D
authors.initials: CD
authors.lastname: Ling
authors.forename: Samuel
authors.initials: S
authors.lastname: Liu
authors.forename: Max
authors.initials: M
authors.lastname: Avdeev
authors.forename: Zhaoming
authors.initials: Z
authors.lastname: Zhang
authors.forename: Gabriel J
authors.initials: GJ
authors.lastname: Cuello
authors.forename: Anton
authors.initials: A
authors.lastname: Tadich
authors.forename: Ling-Yun
authors.initials: LY
authors.lastname: Jang