Giant Polarizability and Origin of Ferroelectricity in Layered Materials with a Litharge-Type Structural Unit.
basic_science · Level V
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- Record sourced from PubMed, PMID 40013939.
- Also identified by DOI 10.1021/acs.nanolett.5c00569.
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Abstract
We discover that a large family of [Pb<sub>2</sub>F<sub>2</sub>]- and [Bi<sub>2</sub>O<sub>2</sub>]-based mixed-anion materials with a litharge-type structural unit are highly polarizable layered semiconductors in proximity to strain-induced ferroelectricity. First-principles calculations demonstrate that in this family of materials, compounds as diverse as PbFBr, BiOCl, BiCuOSe, Bi<sub>2</sub>OS<sub>2</sub>, and Bi<sub>5</sub>O<sub>4</sub>S<sub>3</sub>Cl exhibit static dielectric constants an order of magnitude higher than typical semiconductors. Additionally, they undergo a ferroelectric transition when subjected to a few percent of tensile strain. The ferroelectric transitions of these materials are found to have a universal origin in the strong cross-bandgap hybridization of the cation <i>p</i> orbitals, enabled by the cation 6s<sup>2</sup> lone-pair electrons and the litharge-type structure of the [Pb<sub>2</sub>F<sub>2</sub>] and [Bi<sub>2</sub>O<sub>2</sub>] layers, as demonstrated by the strain-induced ferroelectric transition in the archetypal litharge α-PbO. These results establish materials with a litharge-type structural unit as a large and versatile family of highly polarizable layered semiconductors in proximity to ferroelectricity.