Abstract
The atomic structures of the lanthanide tantalates, Ln3TaO7, series (Ln = Pr, Tb, Dy, Ho, Tm, Yb) were systematically investigated using total scattering techniques. High-energy X-ray and neutron diffraction analysis revealed that the long-range structures can be grouped into three distinct families: (1) ordered Cmcm (Ln = Pr), (2) ordered Ccmm (Ln = Tb, Dy, Ho), and (3) disordered, defect-fluorite Fm3̄m (Ln = Ho, Tm, Yb). These findings help to clarify the symmetry discrepancy for the already reported long-range structures in the literature. The short-range analysis of neutron total scattering data via pair distribution functions reveals a high degree of structural heterogeneity across length scales for all compounds, with distinct local atomic arrangements that are not fully captured by the average, long-range structure. The short-range structures at the level of coordination polyhedra are better captured by a set of alternative non-centrosymmetric structural models: (1) C2cm, (2) C2221, and (3) C2mm. This establishes a short-range multiferroic character for weberite-type tantalates because ferroelectric interactions compete with magnetic correlations. These ferroelectric interactions are particularly pronounced for the disordered compounds Tm3TaO7 and Yb3TaO7. The structural differences among the three families are the result of changes in TaO6 polyhedral tilt (transition between families 1 and 2) and dipolar interactions of off-centered Ta cations (transition between families 2 and 3).
Original language | English |
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Pages (from-to) | 8886-8903 |
Number of pages | 18 |
Journal | Journal of Materials Chemistry A |
Volume | 11 |
Issue number | 16 |
DOIs | |
State | Published - Apr 4 2023 |
Funding
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award DE-SC0020321. Partial support was provided by the Joint PhD Programme of Université Paris-Saclay as part of the Investissements d'Avenir Program, grant number ANR-11-IDEX-003. This work was also supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under the SCGSR Fellowship Program. The SCGSR Program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract number DESC0014664. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. These experiments and analyses were supported by the U.S. Department of Energy (DOE) Office of Fusion Energy Sciences under Contract No. DE-SC0018322 with the Research Foundation for the State University of New York at Stony Brook. This research used resources at the Pair Distribution Function Beamline of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. Authors express their appreciation to Mason King for his support regarding sample synthesis.