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Cation exchange as a mechanism to engineer polarity in layered perovskites

DOI: 10.1021/acs.chemmater.8b04136 DOI Help

Authors: Tong Zhu (University of Oxford) , Guru Khalsa (Cornell University) , Dana M. Havas (Cornell University) , Alexandra Gibbs (ISIS Facility) , Weiguo Zhang (University of Houston) , P. Shiv Halasyamani (University of Houston) , Nicole A. Benedek (Cornell University) , Michael A. Hayward (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials

State: Published (Approved)
Published: November 2018
Diamond Proposal Number(s): 13284

Abstract: Cation exchange reactions performed on the n = 2 Dion-Jacobson phases RbNdNb2O7 and RbNdTa2O7, using LiNO3 and NaNO3, yield the corresponding LiNdM2O7 and NaNdM2O7 (M = Nb, Ta) phases. Synchrotron X-ray and neutron powder diffraction data, in combination with second-harmonic generation data and supported by first-principles DFT calculations, reveal that the LiNdM2O7 phases adopt n = 2 Ruddlesden-Popper type structures with an aˉaˉc+/-(aˉaˉc+) distortion described in the polar space group B2cm. In contrast the NaNdM2O7 phases adopt n = 2 Ruddlesden-Popper type structures with an aˉb0c0/b0aˉc0 distortion, described in the centrosymmetric space group P42/mnm. The differing structures adopted by the LiNdM2O7 and NaNdM2O7 phases are rationalized on the basis of a completion between i) optimizing the size Li/Na coordination site via octahedral tilting and ii) ordering the Na/Li cations within the (Li/Na)O2 sheets to minimize cation-cation repulsion – the former appears to be the dominant factor for the Li phases and the latter factor dominates for the Na phases. The strong A’-cation dependence of the tilting distortions adopted by the A’NdM2O7 phases suggests that by careful selection of the substituting cation the tilting distortions of layered perovskite phases can be rationally tuned to adopt polar configurations, and thus new ferroelectric phases can be synthesized.

Subject Areas: Chemistry, Materials

Instruments: I11-High Resolution Powder Diffraction