Thickness-confined metastable phase transitions drive large piezoelectricity in ultrathin BiFeO<sub>3</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41824566.
- Also identified by DOI 10.1126/sciadv.aeb7174 and PMC identifier 12985725.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Pursuing high-performance lead-free piezoelectrics beyond classical thickness limits remains challenging. This study identifies a transitional phase between rhombohedral and tetragonal structures in strained ultrathin BiFeO<sub>3</sub> layers within (BiFeO<sub>3</sub>/Ca<sub>0.96</sub>Ce<sub>0.04</sub>MnO<sub>3</sub>)<sub>4</sub> multilayer films grown on LaAlO<sub>3</sub> substrates. Atom-scale studies and quantitative electromechanical atomic force microscopy revealed that the transitional phase facilitates continuous polarization rotation in ultrathin BiFeO<sub>3</sub> layers. This effect enhances the piezoelectric responses of the multilayer films and yields a giant piezoelectric coefficient (<i>d</i><sub>33</sub> ≈ 30 picometers per volt) for films containing 16-unit cell BiFeO<sub>3</sub> layers, which is over four times higher than conventional rhombohedral BiFeO<sub>3</sub>. Phase-field simulations confirmed a thickness-dependent electromechanical coupling regularity, behaving as the coexistence of transitional/tetragonal mixed phases and dense nanodomains in strained ultrathin BiFeO<sub>3</sub> layers. This work breaks the thickness limit of single-layer BiFeO<sub>3</sub> for electromechanical applications and proposes a thickness-domain design strategy for lead-free piezoelectric heterostructures.