Oxygen vacancy enhanced ferroelectricity in BTO:SRO nanocomposite films

The enhancement of ferroelectric properties in lead-free ferroelectric is usually achieved by strain engineering. Here, we report a surprising polarization enhancement effect in an isostructural ferroelectric nanocomposite system composited by the ferroelectric material of BaTiO3 and metallic non-ferroelectric oxide of SrRuO3. BaTiO3:SrRuO3 (BTO:SRO) ferroelectric nanocomposite films with the volume ratio of nanogranular SRO ranging from 0 to 16% grown on the Nb-doped SrTiO3 (NSTO) single-crystal substrates by pulsed laser deposition (PLD) are investigated. Robust ferroelectric polarization is observed with a remanent polarization of about 40 mu C/cm(2), comparable to those found in Pb(ZrxTi1-x)O-3 thin films. By combining X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), density functional theory (DFT) calculations, and phase-field simulation, a hypothesis has been proposed that the polarization enhancement may be mainly attributed to the accumulation of oxygen vacancies at the BTO/SRO interface rather than lattice mismatch strain. The novel mechanism of polarization enhancement opens new possibilities for designing future ferroelectric devices. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.