Electrostriction-driven phase instability enables giant pseudo-piezoelectricity in Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2X</sub>.

Bergne, Achilles; Vasiljevic, Milica; Alikin, Denis; Tinti, Victor Buratto; Oliveira, Leonardo; Landberg Hill, Megan O; Chen, Huaiyu; Wallentin, Jesper et al. · Sci Adv · 2026

basic_science · Level V

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Abstract

The electromechanical properties of hafnium zirconium oxide fluorite (Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub>, HZO) remain largely unexplored despite its widespread use as a ferroelectric in CMOS-compatible devices. Here, we demonstrate that electrostriction-driven phase instability enables a giant pseudo-piezoelectric response in epitaxial HZO thin films. Above a critical field of 24 kilovolts per centimeter, field-induced transitions between nonpolar and polar phases activate an extrinsic piezoelectric response of ~1000 picometers per volt and bias-stabilized pseudo-piezoelectric strains exceeding 10,000 picometers per volt. This behavior arises from a combination of large electrostriction (<i>M</i> = 1 × 10<sup>-14</sup> square meters per square volt), ferroelastic softness, and structural reconfiguration, rather than intrinsic polarization switching. Multimodal characterization combining interferometry, diffraction methods, scanning probe microscopy, and first-principles modeling confirms the coupling between strain and metastable phase dynamics. These findings reveal a previously unrecognized mechanism for functional strain generation in fluorite oxides, positioning HZO as a versatile platform for strain-engineered actuators, adaptive metasurfaces, and reconfigurable nanoelectromechanical systems.