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arXiv · 2511.01241

Switchable Polarization in an A-site Deficient Perovskite through Vacancy and Cation Engineering

Suguru Yoshida·Olivier Hernandez·Jinsuke Miyake·Kei Nakayama·Ryo Ishikawa·Hajime Hojo·Yuichi Ikuhara·Venkatraman Gopalan·Katsuhisa Tanaka·Koji Fujita
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Abstract

While defects are unavoidable in crystals and often detrimental to material performance, they can be a key ingredient for inducing functionalities when tailored. Here, we demonstrate that an A-site-deficient perovskite Y$_{1/3}$TaO$_3$ exhibits room-temperature ferroelectricity in a $Pb2_1m$ phase, enabled by ordered vacancies coupled with TaO$_6$ octahedral rotations. Defect-ordered perovskites are frequently trapped in centrosymmetric incommensurate states due to competing structural instabilities; we circumvent this by favoring rotational over polar instability through compositional selection. Unlike canonical improper ferroelectrics that are \textit{ferrielectric}, the vanishing dipoles on vacancy layers in Y$_{1/3}$TaO$_3$ allow for a net ferroelectric alignment of local dipoles, resulting in enhanced polarization. Upon heating, Y$_{1/3}$TaO$_3$ transforms to a paraelectric incommensurate phase at $\simeq$750 K, whose atomic arrangement mirrors the domain topology observed in hybrid improper ferroelectrics. Superspace analysis of the modulated phase reveals a route to improve room-temperature polarization, achieved through epitaxial strain, as confirmed by our lattice-dynamics calculations. This defect-ordering strategy should be generalizable to other improper ferroelectrics, including magnetoelectric multiferroics, providing a pathway to amplify otherwise limited macroscopic polarization.

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Suguru Yoshida, Olivier Hernandez, Jinsuke Miyake, Kei Nakayama, Ryo Ishikawa, Hajime Hojo, Yuichi Ikuhara, Venkatraman Gopalan, Katsuhisa Tanaka, Koji Fujita. 2025-11-03. Switchable Polarization in an A-site Deficient Perovskite through Vacancy and Cation Engineering. https://doi.org/10.1021/jacs.5c19790

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