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Competing Polar and Antipolar Structures in the Ruddlesden-Popper Layered Perovskite Li2SrNb2O7



Ritesh Uppuluri, Hirofumi Akamatsu, Arnab Sen Gupta, Huaiyu Wang, Craig Brown, Kleyser E. Agueda Lopez, Nasim Alem, Venkatraman Gopalan, Thomas E. Mallouk


Over the past few years, several studies have reported the existence of polar phase in n=2 Ruddlesden-Popper layer perovskites by trilinear coupling of oxygen octahedral rotations (OOR) and polar distortions, a phenomenon termed as hybrid improper ferroelectricity. This phenomenon has opened an avenue to expand the available compositions of ferroelectric and piezoelectric layered oxides. In this study, we report a new polar n=2 Ruddlesden-Popper layered niobate, Li2SrNb2O7, which undergoes a structural transformation to an antipolar phase when cooled to 90 K. This structural transition results from a change in the phase of rotation of the octahedral layers within the perovskite slabs across the interlayers. First-principles calculations predicted that the antipolar Pnam phase would compete with the polar a21am phase and that both would be energetically lower than the previously assigned centrosymmetric Amam phase. This phase transition was experimentally observed by a combination of synchrotron X-ray diffraction, powder neutron diffraction, electrical and non-linear optical characterization techniques. The competition between symmetry breaking to yield polar layer perovskites and hybrid improper antiferroelectrics provides new insight into the rational design of antiferroelectric materials that can have applications as supercapacitors for energy storage.
Chemistry of Materials


polar, niobate, improper ferroelectricity, Crystsl structure


Uppuluri, R. , Akamatsu, H. , Gupta, A. , Wang, H. , Brown, C. , Agueda Lopez, K. , Alem, N. , Gopalan, V. and Mallouk, T. (2019), Competing Polar and Antipolar Structures in the Ruddlesden-Popper Layered Perovskite Li<sub>2</sub>SrNb<sub>2</sub>O<sub>7</sub>, Chemistry of Materials, [online], (Accessed July 20, 2024)


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Created June 24, 2019, Updated October 12, 2021