Electric field and temperature induced local polarization switching and piezoresponse in Bi0.88Sm0.12FeO3 ceramics for nanoscale applications

The fundamental understanding of polarization switching in ferroelectric materials is very critical for the development of ferroelectric devices. Electric field and temperature induced nanoscale polarization switching has been studied in polycrystalline Bi0.88Sm0.12FeO3 ceramics using piezoresponse force microscopy (PFM). High resolution synchrotron X-ray diffraction, Rietveld refinements and micro-Raman spectra indicate the phase coexistence of rhombohedral R3c and orthorhombic PlaZrO(3)-like structures at room temperature. Temperature dependent Raman spectra exhibit nonpolar Pnma phase-like vibrational bands at 175 degrees C. The PFM amplitude and phase images revealed irregular multi-grain and domain boundaries with oppositely oriented polarizations which are 180 degrees apart in-phase. Step-wise application of negative and positive tip biases indicates that the 109 degrees polarization switching is more favorable at low fields due to large electric and activation energies associated with 180 degrees switching. PFM in-plane (IP) and out-of-plane (OP) images at different temperatures show the 180 degrees domain growth up to 150 degrees C. The drastic change in the in-plane phase contrast at 175 degrees C indicates the formation of 71 degrees ferroelastic domains affirming the phase transition. Temperature dependent phase and amplitude measurements exhibit typical hysteresis and butterfly loops below the transition temperature signifying ferroelectric-like piezoelectric behavior. The sudden decrease in the amplitude value at 175 degrees C supports a phase transition to non-polar phase where piezoeresponse would be nearly zero. However, there exist non-zero piezoresponse regions at 200 degrees C implying that ferroelectric clusters are embedded in nonpolar phase which make the material ferroelectrically active at nanoscale level. (C) 2019 Elsevier B.V. All rights reserved.