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Mallick S, Orlandi F, Manuel P, Zhang W, Halasyamani PS, Hayward MA. MnCaTa 2O 7-A Magnetically Ordered Polar Phase Prepared via Cation Exchange. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2023; 35:7839-7846. [PMID: 37780409 PMCID: PMC10538500 DOI: 10.1021/acs.chemmater.3c01850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 08/30/2023] [Indexed: 10/03/2023]
Abstract
Reaction between the pseudo-Ruddlesden-Popper phase Li2CaTa2O7 and MnCl2 at 375 °C yields MnCaTa2O7, a paramagnetic polar phase (space group P21nm), which adopts an a-b-c+/b-a-c+ distorted, layered perovskite structure. Magnetization and neutron diffraction data show that MnCaTa2O7 adopts an antiferromagnetically ordered state below TN = 56 K and exhibits large lattice parameter anomalies and a transient increase in its polar distortion mode at TA = 50 K. However, in contrast to the related phase MnSrTa2O7, MnCaTa2O7 shows no strong signature of weak ferromagnetism and thus shows no signs of magnetoelectric coupling. The differences in physical behavior between the two MnATa2O7 phases appear to be related to their differing Mn cation-order and differing TaO6 tilting schemes and demonstrate that even subtle changes to these orderings can have large effects on the distortion-mode couplings, which drive complex behavior of this class of "hybrid improper" ferroelectric material.
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Affiliation(s)
- Subhadip Mallick
- Department
of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Fabio Orlandi
- ISIS
Facility, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, UK
| | - Pascal Manuel
- ISIS
Facility, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, UK
| | - Weiguo Zhang
- Department
of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204-5003, United States
| | - P. Shiv Halasyamani
- Department
of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204-5003, United States
| | - Michael A. Hayward
- Department
of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
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Mallick S, Zhang W, Batuk M, Gibbs AS, Hadermann J, Halasyamani PS, Hayward MA. The crystal and defect structures of polar KBiNb 2O 7. Dalton Trans 2022; 51:1866-1873. [PMID: 35018920 DOI: 10.1039/d1dt04064b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
KBiNb2O7 was prepared from RbBiNb2O7 by a sequence of cation exchange reactions which first convert RbBiNb2O7 to LiBiNb2O7, before KBiNb2O7 is formed by a further K-for-Li cation exchange. A combination of neutron, synchrotron X-ray and electron diffraction data reveal that KBiNb2O7 adopts a polar, layered, perovskite structure (space group A11m) in which the BiNb2O7 layers are stacked in a (0, ½, z) arrangement, with the K+ cations located in half of the available 10-coordinate interlayer cation sites. The inversion symmetry of the phase is broken by a large displacement of the Bi3+ cations parallel to the y-axis. HAADF-STEM images reveal that KBiNb2O7 exhibits frequent stacking faults which convert the (0, ½, z) layer stacking to (½, 0, z) stacking and vice versa, essentially switching the x- and y-axes of the material. By fitting the complex diffraction peak shape of the SXRD data collected from KBiNb2O7 it is estimated that each layer has approximately a 9% chance of being defective - a high level which is attributed to the lack of cooperative NbO6 tilting in the material, which limits the lattice strain associated with each fault.
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Affiliation(s)
- Subhadip Mallick
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
| | - Weiguo Zhang
- Department of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204-5003, USA
| | - Maria Batuk
- EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - Alexandra S Gibbs
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, UK
| | - Joke Hadermann
- EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - P Shiv Halasyamani
- Department of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204-5003, USA
| | - Michael A Hayward
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
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