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Switching between proper and hybrid-improper polar structures via cation substitution in A2La(TaTi)O7 (A = Li, Na)

DOI: 10.1021/acs.chemmater.1c00599 DOI Help

Authors: Subhadip Mallick (University of Oxford) , Andrew Dominic Fortes (ISIS Facility) , Weiguo Zhang (University of Houston) , P. Shiv Halasyamani (University of Houston) , Michael A. Hayward (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials , VOL 23

State: Published (Approved)
Published: March 2021
Diamond Proposal Number(s): 18786

Abstract: Neutron powder diffraction data indicate that Li2La(TaTi)O7 adopts a polar, a–a–c+/a–a–c+ distorted, n = 2 Ruddlesden–Popper structure described in space group A21am (#36), consistent with a hybrid-improper stabilization of the polar structure via a trilinear coupling between the X3–, X2+, and Γ5– distortion modes. In contrast, Na2La(TaTi)O7 adopts a polar, a–a–c–/a–a–(-c–) distorted, n = 2 Ruddlesden–Popper structure described in space group Pna21 (#33) with the polar Γ3– distortion mode apparently stabilized by a second-order Jahn–Teller distortion of the d0 Ta5+/Ti4+ cations. The change in class of polar distortion of the A2La(TaTi)O7 framework, from hybrid improper (trilinearly coupled) to proper (second-order Jahn–Teller stabilized), on A-cation substitution suggests that the two stabilization mechanisms are in competition in these two materials and many other hybrid-improper ferroelectric phases.

Subject Areas: Materials, Chemistry

Instruments: I11-High Resolution Powder Diffraction

Other Facilities: ISIS

Discipline Tags:

Quantum Materials Multiferroics Chemistry Material Sciences

Technical Tags:

Diffraction Single Crystal X-ray Diffraction (SXRD)