Nanoscale mapping of heterogeneity of the polarization reversal in lead-free relaxor–ferroelectric ceramic composites

Abstract

Relaxor/ferroelectric ceramic/ceramic composites have shown to be promising in generating large electromechanical strain at moderate electric fields. Nonetheless, the mechanisms of polarization and strain coupling between grains of different nature in the composites remain unclear. To rationalize the coupling mechanisms we performed advanced piezoresponse force microscopy (PFM) studies of 0.92BNT-0.06BT-0.02KNN/0.93BNT-0.07BT (ergodic/non-ergodic relaxor) composites. PFM is able to distinguish grains of different phases by characteristic domain patterns. Polarization switching has been probed locally, on a sub-grain scale. k-Means clustering analysis applied to arrays of local hysteresis loops reveals variations of polarization switching characteristics between the ergodic and non-ergodic relaxor grains. We report a different set of switching parameters for grains in the composites as opposed to the pure phase samples. Our results confirm ceramic/ceramic composites to be a viable approach to tailor the piezoelectric properties and optimize the macroscopic electromechanical characteristics.

Structure and Electrical Properties of Na0.5Bi0.5TiO3 Epitaxial Films with (110) Orientation

“…The mainstay ferroelectric materials for applications have traditionally been the Pb(Zr,Ti)O 3 (PZT) films due to their excellent performance (large remnant polarization P r and small coercive field E C ). However, the use of lead gives rise to environmental concerns, which is the driving force for the development of alternative lead-free ferroelectric materials [6][7][8]. Na 0.5 Bi 0.5 TiO 3 (NBT) with good ferroelectric properties and high Curie temperature has been considered to be an excellent candidate to replace lead-based ferroelectric materials [9][10][11].…”

Multilayer lead‐free piezoceramic composites: Influence of co‐firing on microstructure and electromechanical behavior

“…In lead‐free composites, transmission electron microscopy (TEM) investigations have shown at least two different types of grains, which was attributed to the presence of chemically distinct seed and matrix grains . Piezoelectric force microscopy (PFM) investigations of the same composite system have stated that intermixing of the constituents, especially close to grain boundaries, cannot be excluded due to evidence that the “ergodic grains” measured in this study exhibited broader hysteresis loops than those of pure ergodic relaxor materials, indicating that the ergodic grains were altered by the nonergodic grains through nanometer sized‐inclusions distributed in the surrounding ER matrix . However, a quantitative investigation of chemical composition across multiple grains by TEM has proven challenging due to the submicron length scale at which diffusion occurs as well as the similarity in chemical composition between seed and matrix .…”

Polar domain structural evolution under electric field and temperature in the (Bi0.5Na0.5)TiO3‐0.06BaTiO3 piezoceramics

“…Therefore, compositions with x from 0 to 0.08 are prepared in this work and the MPB composition is determined to be at x = 0.06 (BNT‐6BT) with the highest permittivity and piezoelectric coefficient. The domain‐related study is performed by the piezoresponse force microscopy (PFM), in which a high spatial resolution is achieved using a sharp conductive tip, offering a nondestructive way to study both the out‐of‐plane and in‐plane domain structures in polycrystalline materials at various temperatures. We aim to investigate the behavior of BNT‐BT under electric field from a multiscale approach, and to provide better understanding in the mechanism of the electrical properties in BNT‐BT solid solutions at the MPB in relation to its complex morphotropic structure.…”