Phys.org December 5, 2024
Strong coupling between polarization (P) and strain (É›) in ferroelectric complex oxides offers unique opportunities to dramatically tune their properties. An international team of researchers (USA – Pennsylvania State University, Cornell University, Stanford University, University of Nebraska, Argonne National Laboratory, Belgium, Germany) demonstrated strain tuning of ferroelectricity in epitaxial potassium niobate (KNbO3) thin films grown by sub-oxide molecular beam epitaxy. While bulk KNbO3 exhibited three ferroelectric transitions and a Curie temperature (Tc) of ≈676 K, phase-field modeling predicted that a biaxial strain pushes its Tc > 975 K, its decomposition temperature in air, and for −1.4% strain, to Tc > 1325 K, its melting point. Ferroelectric measurements, and transmission electron microscopy revealed a single tetragonal phase from 10 K to 975 K, an enhancement in the tetragonal phase remanent polarization, and a ≈200% enhancement in its optical second harmonic generation coefficients over bulk values. According to the researchers these properties in a lead-free system make it an attractive candidate for applications ranging from high-temperature ferroelectric memory to cryogenic temperature quantum computing… read more. Open Access TECHNICAL ARTICLEÂ
a) Schematic of second harmonic generation (SHG) set up in reflection… Credit: Advanced Materials, 12 November 2024