Engineering Relaxor Behavior in (BaTiO 3 ) n /(SrTiO 3 ) n Superlattices.
Eduardo LupiRobert B WexlerDerek MeyersAnton ZahradnikYizhe JiangSandhya SusarlaRamamoorthy RameshLane W MartinAndrew M RappePublished in: Advanced materials (Deerfield Beach, Fla.) (2023)
Complex-oxide superlattices provide a pathway to numerous emergent phenomena because of the juxtaposition of disparate properties and the strong interfacial interactions present in these unit-cell-precise structures. This is particularly true in superlattices of ferroelectric and dielectric materials, wherein new forms of ferroelectricity, exotic dipolar textures, and distinctive domain structures can be produced. Here, relaxor-like behavior, which is typically associated with the chemical inhomogeneity and complexity of solid solutions, is observed in (BaTiO 3 ) n /(SrTiO 3 ) n (n = 6-20 unit cells) superlattices. Dielectric studies and subsequent Vogel-Fulcher analysis show significant frequency dispersion of the dielectric maximum across a range of periodicities, with enhanced dielectric constant and more robust relaxor behavior for smaller period n. Bond valence molecular-dynamics simulations predict the relaxor-like behavior observed experimentally, and interpretations of the polar patterns via 2D discrete-wavelet transforms in shorter-period superlattices suggest that the relaxor behavior arises from shape variations of the dipolar configurations, in contrast to frozen antipolar stripe domains in longer-period superlattices (n = 16). Moreover, the size and shape of the dipolar configurations are tuned by superlattice periodicity, thus providing a definitive design strategy to use superlattice layering to create relaxor-like behavior which may expand the ability to control desired properties in these complex systems. This article is protected by copyright. All rights reserved.
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