Protonation-Driven Polarization Retention Failure in Nano-Columnar Lead-Free Ferroelectric Thin Films.

Understanding microscopic mechanisms of polarization retention characteristics in ferroelectric thin films is of great significance for exploring unusual physical phenomena inaccessible in the bulk counterparts and for realizing thin-film-based functional electronic devices. Perovskite (K,Na)NbO is an excellent class of lead-free ferroelectric oxides attracting tremendous interest thanks to its potential applications to nonvolatile memory and eco-friendly energy harvester/storage. Nonetheless, in-depth investigation of ferroelectric properties of (K,Na)NbO films and the following developments of nano-devices are limited due to challenging thin-film fabrication associated with nonstoichiometry by volatile K and Na atoms.

Ferroelectric Polymer Nanofibers Reminiscent of Morphotropic Phase Boundary Behavior for Improved Piezoelectric Energy Harvesting.

Ferroelectric and piezoelectric polymers have attracted great attention from many research and engineering fields due to its mechanical robustness and flexibility as well as cost-effectiveness and easy processibility. Nevertheless, the electrical performance of piezoelectric polymers is very hard to reach that of piezoelectric ceramics basically and physically, even in the case of the representative ferroelectric polymer, poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)). Very recently, the concept for the morphotropic phase boundary (MPB), which has been exclusive in the field of high-performance piezoelectric ceramics, has been surprisingly confirmed in P(VDF-TrFE) piezoelectric copolymers by the groups.

Strain-Gradient Effect in Gas Sensors Based on Three-Dimensional Hollow Molybdenum Disulfide Nanoflakes.

A novel three-dimensional transition metal dichalcogenide (TMD) structure consisting of seamless hollow nanoflakes on two-dimensional basal layers was synthesized by a one-step chemical vapor deposition method. Here, we demonstrate that the as-grown nanoflakes are formed on an organic promoter layer which served as a positive template and are swollen at the grain boundaries by the bubbling effect. TMD nanosheets with hollow nanoflakes are successfully applied as chemical sensors, and it was found that their gas adsorption property is strongly related to the internal strain gradient resulting from the variation in the lattice parameter.

Flexible Piezoelectric Generators by Using the Bending Motion Method of Direct-Grown-PZT Nanoparticles on Carbon Nanotubes.

Recently, composite-type nanogenerators (NGs) formed from piezoelectric nanostructures and multi-walled carbon nanotubes (CNTs), have become one of the excellent candidates for future energy harvesting because of their ability to apply the excellent electrical and mechanical properties of CNTs. However, the synthesis of NG devices with a high proportion of piezoelectric materials and a low polymer content, such as of polydimethylsiloxane (PDMS), continues to be problematic. In this work, high-piezoelectric-material-content flexible films produced from Pb(Zr,Ti)O₃ (PZT)-atomically-interconnected CNTs and polytetrafluoroethylene (PTFE) are presented.

Rapid and direct synthesis of complex perovskite oxides through a highly energetic planetary milling.

The search for a new and facile synthetic route that is simple, economical and environmentally safe is one of the most challenging issues related to the synthesis of functional complex oxides. Herein, we report the expeditious synthesis of single-phase perovskite oxides by a high-rate mechanochemical reaction, which is generally difficult through conventional milling methods. With the help of a highly energetic planetary ball mill, lead-free piezoelectric perovskite oxides of (Bi, Na)TiO, (K, Na)NbO and their modified complex compositions were directly synthesized with low contamination.

Toward Arbitrary-Direction Energy Harvesting through Flexible Piezoelectric Nanogenerators Using Perovskite PbTiO Nanotube Arrays.

New fiber-type piezoelectric nanogenerator devices consisting of radially aligned perovskite PbTiO nanotubes are designed for energy harvesting from arbitrary mechanical motion. The free-standing fiber-type nanogenerators generate constant amount of electric power by bending or wind motion regardless of direction, thus, extending the possibility of their practical applications.

Nanogenerators consisting of direct-grown piezoelectrics on multi-walled carbon nanotubes using flexoelectric effects.

We report the first attempt to prepare a flexoelectric nanogenerator consisting of direct-grown piezoelectrics on multi-walled carbon nanotubes (mwCNT). Direct-grown piezoelectrics on mwCNTs are formed by a stirring and heating method using a Pb(Zr0.52Ti0.

Effects of sintering temperature on the pyrochlore phase in PZT nanotubes and their transformation to the perovskite phase by coating with PbO multilayers.

We report the phase evolution of Pb(Zr0.52Ti0.48)O3 nanotubes (PZT-NTs), from the pyrochlore to perovskite phase, with an outer diameter of about 420 nm and a wall thickness of about 10 nm.

Flexoelectric control of defect formation in ferroelectric epitaxial thin films.

Flexoelectric control of defect formation and associated electronic function is demonstrated in ferroelectric BiFeO3 thin films. An intriguing, so far never demonstrated, effect of internal electric field (Eint ) on defect formation is explored by a means of flexoelectricity. Our study provides novel insight into defect engineering, as well as allows a pathway to design defect configuration and associated electronic function.

Flexoelectric effect in the reversal of self-polarization and associated changes in the electronic functional properties of BiFeO(3) thin films.

Flexoelectricity can play an important role in the reversal of the self-polarization direction in epitaxial BiFeO3 thin films. The flexoelectric and interfacial effects compete with each other to determine the self-polarization state. In Region I, the self-polarization is downward because the interfacial effect is more dominant than the flexoelectric effect.

Nanopore domain growth behavior by nanopore changes near domain boundaries in porous anodic alumina.

We investigate the nanopore changes near domain boundaries during the nanopore growth in porous anodic alumina (PAA) to understand the domain growth behavior with the anodization time. In order to observe the pore changes with the time, we analyze cleavage planes of PAA according to the nanopore length using a field emission scanning electron microscopy. The domain growth can be explained with three kinds of nanopore changes observed near domain boundaries: a change of pore diameter, a pore-branching, and a pore-movement.

Ferroelectricity in highly ordered arrays of ultra-thin-walled Pb(Zr,Ti)O3 nanotubes composed of nanometer-sized perovskite crystallites.

We report the first unambiguous ferroelectric properties of ultra-thin-walled Pb(Zr,Ti)O 3 (PZT) nanotube arrays, each with 5 nm thick walls and outer diameters of 50 nm. Ferroelectric switching behavior with well-saturated hysteresis loops is observed in these ferroelectric PZT nanotubes with P r and E c values of about 1.5 microC cm (-2) and 86 kV cm (-1), respectively, for a maximum applied electric field of 400 kV cm (-1).