We investigated domain kinetics by measuring the polarization switching behaviors of polycrystalline Pb(Zr,Ti)O3 films, which are widely used in ferroelectric memory devices. Their switching behaviors at various electric fields and temperatures could be explained by assuming the Lorentzian distribution of domain switching times. We viewed the switching process under an electric field as a motion of the ferroelectric domain through a random medium, and we showed that the local field variation due to dipole defects at domain pinning sites could explain the intriguing distribution.PACS numbers: 77.80. Fm, 77.80.Dj, 77.84.Dy Domain switching kinetics in ferroelectrics (FEs) under an external electric field E ext have been extensively investigated for several decades [1,2,3,4,5,6,7,8,9]. The traditional approach to explain the FE switching kinetics, often called the Kolmogorov-Avrami-Ishibashi (KAI) model, is based on the classical statistical theory of nucleation and unrestricted domain growth [10,11]. For a uniformly polarized FE sample under E ext , the KAI model gives the time (t)-dependent change in polarization ∆P (t) aswhere n and t 0 are the effective dimension and characteristic switching time for the domain growth, respectively, and P s is spontaneous polarization. When the nuclei are appearing in time with the same probability, n = 3 for bulk samples and n = 2 for thin films [12]. In addition, t 0 is proportional to the average distance between the nuclei, divided by the domain wall speed. Several studies have used the KAI model successfully to explain the ∆P (t) behaviors of FE single crystals and epitaxial thin films [2]. Recently, FE thin films have been intensively investigated for FE random access memory (FeRAM) [1]. Most commercial FeRAM use polycrystalline Pb(Zr,Ti)O 3 (poly-PZT) films, and their ∆P (t) behaviors determine the reading and writing speeds of the FeRAM. In such non-epitaxial FE films, a domain cannot propagate indefinitely due to pinning caused by numerous defects, so the KAI model cannot be applied. Therefore, it is important both scientifically and technologically to clarify the domain switching kinetics of polycrystalline FE films.Numerous studies have examined the ∆P (t) behaviors of polycrystalline FE films, and the reported results vary markedly [3,4,5,6,7]. Lohse et al. measured the polarization switching currents of poly-PZT films, and showed that ∆P (t) slowed significantly compared to Eq. (1) [3]. Tagantsev et al. observed similar phenomena for poly-PZT films. To explain these behaviors, they developed the nucleation-limited-switching (NLS) model. They assumed that films consist of several areas that have independent switching kinetics:where F (log t 0 ) is the distribution function for log t 0 [4]. They assumed a very broad mesa-like function for F (log t 0 ), and could explain their ∆P (t) data. The same

In the past two decades, mechanical energy harvesting technologies have been developed in various ways to support or power small-scale electronics. Nevertheless, the strategy for enhancing current and charge performance of flexible piezoelectric energy harvesters using a simple and cost-effective process is still a challenging issue. Herein, a 1D-3D (1-3) fully piezoelectric nanocomposite is developed using perovskite BaTiO (BT) nanowire (NW)-employed poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) for a high-performance hybrid nanocomposite generator (hNCG) device. The harvested output of the flexible hNCG reaches up to ≈14 V and ≈4 µA, which is higher than the current levels of even previous piezoceramic film-based flexible energy harvesters. Finite element analysis method simulations study that the outstanding performance of hNCG devices attributes to not only the piezoelectric synergy of well-controlled BT NWs and within P(VDF-TrFE) matrix, but also the effective stress transferability of piezopolymer. As a proof of concept, the flexible hNCG is directly attached to a hand to scavenge energy using a human motion in various biomechanical frequencies for self-powered wearable patch device applications. This research can pave the way for a new approach to high-performance wearable and biocompatible self-sufficient electronics.

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An approach for embedding high-permittivity dielectric thin films into glass epoxy laminate packages has been developed. Lead lanthanum zirconate titanate (Pb 0.85 La 0.15 -(Zr 0.52 Ti 0.48 ) 0.96 O 3 , PLZT) thin films were prepared using chemical solution deposition on nickel-coated copper foils that were 50 m thick. Sputter-deposited nickel top electrodes completed the all-base-metal capacitor stack. After hightemperature nitrogen-gas crystallization anneals, the PLZT composition showed no signs of reduction, whereas the basemetal foils remained flexible. The capacitance density was 300 -400 nF/cm 2 , and the loss tangent was 0.01-0.02 over a frequency range of 1-1000 kHz. These properties represent a potential improvement of 2-3 orders of magnitude over currently available embedded capacitor technologies for polymeric packages.