Abstract:
Ferroelectricity in Hf0.5Zr0.5O2 (HZO) originates from a polymorphic landscape where the metastable orthorhombic phase competes with monoclinic and tetragonal forms, making functional properties highly sensitive to structural instability. Recent strategies have exploited ionic-vacancy mechanisms, either through redox interactions with the environment or by employing ferroionic heterostructures, to enhance ferroelectric performance. Here, we embrace the ferroionic heterostructure approach and demonstrate that dynamic oxygen-vacancy exchange at epitaxial junctions produces an active interplay between ferroelectric and ionic layers. Epitaxial heterostructures with La0.67Sr0.33MnO3-δ (LSMO), yttria-stabilized ZrO2-δ (YSZ), and Gd-doped CeO2-δ (CGO) reveal coupled electro-chemo-mechanical responses, including ferroelectric diode characteristics and subtle lattice distortions. Epitaxial fluorite-fluorite interfaces act as vacancy-exchange gates that bias polymorphism, enhance polarization, strengthen piezoelectric response, and suppress leakage, in contrast to the electronically dominated perovskite-fluorite junctions. These findings show that ferroionic heterostructures host reciprocal vacancy-driven dynamics, establishing them as a platform for defect-programmable ferroelectricity and tunable functionality in hafnia-based oxides.
Title: Electro-Chemo-Mechanical Coupling in Hf0.5Zr0.5O2 Ferroionic Heterostructures
Authors: Achilles Bergne, Denis Alikin, Milica Vasiljevic, Victor B. Tinti, Javier Zamudio-García, Leonardo Soares de Oliveira, Megan Landberg, Dimitrios Koukoulis, Huaiyu Chen, Jesper Wallentin, David Marrero-López, Astri Bjørnetun Haugen, Sizhao Huang, Dennis Christensen, Nini Pryds, Alexander Tselev, Andrei Kholkin, Vincenzo Esposito
Reference: Advanced Functional Materials (2026): e30176
