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Persistent URL http://purl.org/net/epubs/work/49082155
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Record Id 49082155
Title Switching between Proper and Hybrid-Improper Polar Structures via Cation Substitution in A2La(TaTi)O7 (A = Li, Na)
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.
Organisation ISIS , ISIS-HRPD , STFC
Funding Information Welch Foundation (E-1457); University of Oxford
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Language English (EN)
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Journal Article Chem Mater 33, no. 7 (2021): 2666-2672. doi:10.1021/acs.chemmater.1c00599 2021