Large Polarization and Susceptibilities in Artificial Morphotropic Phase Boundary PbZr_1−xTi_xO₃ Superlattices

Abstract

The ability to produce atomically precise, artificial oxide heterostructures allows for the possibility of producing exotic phases and enhanced susceptibilities not found in parent materials. Typical ferroelectric materials either exhibit large saturation polarization away from a phase boundary or large dielectric susceptibility near a phase boundary. Both large ferroelectric polarization and dielectric permittivity are attained wherein fully epitaxial (PbZr0.8Ti0.2O3)n/(PbZr0.4Ti0.6O3)2n (n = 2, 4, 6, 8, 16 unit cells) superlattices are produced such that the overall film chemistry is at the morphotropic phase boundary, but constitutive layers are not. Long‐ (n ≥ 6) and short‐period (n = 2) superlattices reveal large ferroelectric saturation polarization (Ps = 64 µC cm−2) and small dielectric permittivity (εr ≈ 400 at 10 kHz). Intermediate‐period (n = 4) superlattices, however, exhibit both large ferroelectric saturation polarization (Ps = 64 µC cm−2) and dielectric permittivity (εr = 776 at 10 kHz). First‐order reversal curve analysis reveals the presence of switching distributions for each parent layer and a third, interfacial layer wherein superlattice periodicity modulates the volume fraction of each switching distribution and thus the overall material response. This reveals that deterministic creation of artificial superlattices is an effective pathway for designing materials with enhanced responses to applied bias.

Tracking ferroelectric domain formation during epitaxial growth of PbTiO3 films

“…The resulting domain architecture with an increased domain heterogeneity is of fundamental interest for many practical applications 2,18 . When the ferroelectric domain or domain-wall density is high, small increments in the applied voltage can lead to enormous changes in ferroelectric net polarization 36,37 .…”

Beyond Expectation: Advanced Materials Design, Synthesis, and Processing to Enable Novel Ferroelectric Properties and Applications

“…Research efforts have leveraged polarization rotation [56], inversion symmetry breaking [57], and phase-field simulations [58] as a pathway to design and optimize piezoelectric responses. For example, a recent study [59] placed two different ferroelectric phases in the PbZr1-xTixO3 system (from the rhombohedral zirconium-rich and from the tetragonal titanium-rich sides of the phase diagram) and used superlattice design as a proxy for local compositionasking what happens when the overall chemistry is that of the morphotropic phase boundary (MPB), but the individual layers are far away from that boundary? The intimate interfacing of these dissimilar materials resulted in a unique combination of effects: simultaneous large polarization magnitude and large permittivity.…”

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

“…[ 3,8 ] Superlattice structures have even been used in all‐ferroelectric layered structures to enhance ferroelectric polarization and dielectric response simultaneously, as was demonstrated in the PbZr 1− x Ti x O 3 system. [ 9 ] These examples illustrate the expansive design space and the potential to explore behavior beyond previously reported novel phases and to enhance properties in oxide superlattices.…”