Engineering Relaxor Behavior in (BaTiO3)n/(SrTiO3)n Superlattices

Complex‐oxide superlattices provide a pathway to numerous emergent phenomena because of the juxtaposition of disparate properties and the strong interfacial interactions 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, typically associated with the chemical inhomogeneity and complexity of solid solutions, is observed in (BaTiO3)n/(SrTiO3)n (n = 4–20 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. Relaxor‐like behavior, typically associated with chemical inhomogeneity in solid solutions, is experimentally observed across a range of (BaTiO3)n/(SrTiO3)n (n = 4–20 unit cells) superlattices. Bond‐valence molecular‐dynamics simulations suggest that relaxor‐like behavior in shorter‐period superlattices arises from temperature‐driven size variations of antipolar stripe domains in contrast to more thermally stable dipolar configurations in longer‐period superlattices.