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The complex domain structure in ferroelectrics gives rise to electromechanical coupling, and its evolution (via domain switching) results in a time-dependent (i.e. viscoelastic) response. Although ferroelectrics are used in many technological applications, most do not attempt to exploit the viscoelastic response of ferroelectrics, mainly due to a lack of understanding and accurate models for their description and prediction. Thus, the aim of this thesis research is to gain better understanding of the influence of domain evolution in ferroelectrics on their dynamic mechanical response. There have been few studies on the viscoelastic properties of ferroelectrics, mainly due to a lack of experimental methods. Therefore, an apparatus and method called Broadband Electromechanical Spectroscopy (BES) was designed and built. BES allows for the simultaneous application of dynamic mechanical and electrical loading in a vacuum environment. Using BES, the dynamic stiffness and loss tangent in bending and torsion of a particular ferroelectric, viz. lead zirconate titanate (PZT), was characterized for different combinations of electrical and mechanical loading frequencies throughout the entire electric displacement hysteresis. Experimental results showed significant increases in loss tangent (by nearly an order of magnitude) and compliance during domain switching, which shows promise as a new approach to structural damping. A continuum model of the viscoelasticity of ferroelectrics was developed, which incorporates microstructural evolution via internal variables and associated kinetic relations. For the first time, through a new linearization process, the incremental dynamic stiffness and loss tangent of materials were computed throughout the entire electric displacement hysteresis for different combinations of mechanical and electrical loading frequencies. The model accurately captured experimental results. Using the understanding gained from the characterization and modeling of PZT, two applications of domain switching kinetics were explored by using Micro Fiber Composites (MFCs). Proofs of concept of set-and-hold actuation and structural damping using MFCs were demonstrated.
The continued digitalization of our society means that more and more things are getting connected electronically. Since currently used inorganic electronics are not well suited for these new applications because of costs and environmental issues, organic electronics can play an important role here. These essentially plastic materials are cheap to produce and relatively easy to recycle. Unfortunately, their poor performance has so far hindered widespread application beyond displays. One key component of any electronic device is the memory. For organic electronics several technologies are being investigated that could serve as memories. One of these are the ferroelectrics, materials that have a spontaneous electrical polarization that can be reversed with an electric field. This bistable polarization which shows hysteresis makes these materials excellent candidates for use as memories. This thesis focuses on a specific type of organic ferroelectric, the supramolecular discotics. These materials consist of disk?like molecules that form columns in which all dipolar groups are aligned, giving a macroscopic ferroelectric polarization. Of particular interest are the benzenetricarboxamides (BTA), which are used as a model system for the whole class of discotic ferroelectrics. BTA uses a core?shell architecture which allows for easy modification of the molecular structure and thereby the ferroelectric properties. To gain a deeper understanding of the switching processes in this organic ferroelectric BTA, both microscopic and analytical modeling are used. This is supported by experimental data obtained through electrical characterization. The microscopic model reduces the material to a collection of dipoles and uses electrostatics to calculate the probability that these dipoles flip. These flipping rates are the input for a kinetic Monte Carlo simulation (kMC), which simulates the behavior of the dipoles over time. With this model we simulated three different switching processes on experimental time and length scales: hysteresis loops, spontaneous depolarization, and switching transients. The results of these simulations showed a good agreement with experiments and we can rationalize the obtained parameter dependencies in the framework of thermally activated nucleation limited switching (TA?NLS). The microscopic character of the model allows for a unique insight into the nucleation process of the polarization switching. We found that nucleation happens at different locations for field driven polarization switching as compared to spontaneous polarization switching. Field?driven nucleation happens at the contacts, whereas spontaneous depolarization starts at defects. This means that retention times in disordered ferroelectrics could be improved by reducing the disorder, without affecting the coercive field. Detailed analysis of the nucleation process also revealed a critical nucleation volume that decreases with applied field, which explains the Merz?like field?dependence of the switching time observed in experiments. In parallel to these microscopic simulations we developed an analytical framework based on the theory of TA?NLS. This framework is mainly focused on describing the switching transients of disordered ferroelectrics. It can be combined with concepts of the Preisach model, which considers a non?ideal ferroelectric as a collection of ideal hysterons. We were able to relate these hysterons and the distribution in their up? and down?switching fields to the microscopic structure of the material and use the combined models to explain experimentally observed dispersive switching kinetics. Whereas ferroelectrics on their own could potentially serve as memories, the readout of ferroelectric memories becomes easier if they are combined with semiconductors. We have introduced several molecular materials following the same design principle of a core?shell structure, which uniquely combine ferroelectricity and semiconductivity in one material. The experimental IV?curves of these materials could be described using an asymmetric Marcus hopping model and show their potential as memories. The combination of modeling and experimental work in this thesis thereby provides an increased understanding of organic ferroelectrics, which is crucial for their application as memories.
The book examines domain structuring due to the loss of the initial phase stability in materials of finite size. It also covers aspects such as the behaviour of domain boundaries during their interaction with lattice defects, their structure in real ferroelectrically ordered materials, the effect of the lattice potential relief on their movement, and the flexural and translational components of their dynamics in ferroelectric crystals. The contribution of the domain boundaries to the dielectric properties of ferroelectrics and elastic properties of ferroelectric elastomers is evaluated.
In this thesis, in situ biasing experiments on BiFeO3 thin film devices were enabled through the development of a specimen holder and sample electrode mask. The dynamics of ferroelectric domain propagation and nucleation were studied at varying electric fields, and at high spatial and temporal resolution using this in situ technique. A range of dynamic behavior is witnessed in the captured movies, including domain nucleation, propagation, switching, relaxation, and intermediate domain configurations. The dynamic interaction of domains and defects is studied. A network of misfit dislocations at the BFO film-substrate interface is found to alter domain morphologies and velocities. Threading dislocations are shown to stabilize intermediate domain configurations and radically slow domain relaxation, while also acting as pinning sites. A comparison of the observed domain kinetics is made to two popular models -- the Kolmogorov-Avrami-Ishibashi model and Nucleation Limited Switching model. The influence of the arrays of dislocations on the domain kinetics in these BFO thin film devices more accurately fits the NLS model. Investigations into the influence of charged domain walls and charged defect clusters are presented. These findings, by revealing how the presence of defects and localized compositional changes play a role in domain wall motion behavior during electric field control, can help improve the design of future devices built upon ferroelectrics and multiferroics.
Ferroelectricity is a symptom of inevitable electrical polarization changes in materials without external electric field interference. Ferroelectricity is a phenomenon exhibited by crystals with a spontaneous polarization and hysteresis effects associated with dielectric changes when an electric field is given. Our fascination with ferroelectricity is in recognition of a beautiful article by Itskovsky, in which he explains the kinetics of a ferroelectric phase transition in a thin ferroelectric layer (film). We have been researching ferroelectric materials since 2001. There are several materials known for their ferroelectric properties. Barium titanate and barium strontium titanate are the most well known. Several others include tantalum oxide, lead zirconium titanate, gallium nitride, lithium tantalate, aluminium, copper oxide, and lithium niobate. There is still a blue ocean of ferroelectric applications yet to be expounded. It is and hopefully always will be a bright future.
Neutrons are extremely versatile probes for investigating structure and dynamics in condensed matter. Due to their large penetration depth, they are ideal for in-situ measurements of samples situated in sophisticated and advanced environments. The advent of new high-intensity neutron sources and instruments, as well as the development of new real-time techniques, allows the tracking of transformation processes in condensed matter on a microscopic scale. The present volume provides a review of the state of the art of this new and exciting field of kinetics with neutrons.
CONTENTS Preface, XI List of Contributors, XIII Part I. Reports Relation Between the Vacancy-Charge Distribution and the efg in Cubic Perovskite-Type Compounds R.E. Alonso and A. Lopez-Garcia................................................................... 3 Boracites: A Structural Family Presenting a Variety of Ferroic Phase Transitions A.G. Castellanos-Guzman, M. Czank, J. Reyes-Gomez, J. Campa-Molina, Arun Kumar, Gurvinderjit Singh, V.S. Tiwari, and V.K. Wadhawan....................................................................................... 37 Ferroelectric Dram Cell Without a Storage Capacitor Jan-Ping Han.................................................................................................. 73 Investigation of the Two-Dimensional Polar Molecular Assembly Using Multipurpose Nonlinear Optical Microscope Norikata Kato, Kentaro Saito, Toshinori Serata, Hiroaki Aida, and Yoshiaki Uesu ……………………………………………………… 81 Investigation of the Two-Dimensional Polar Molecular Assembly Using Multipurpose Nonlinear Optical Microscope J. K. Krüger, C. Fischer, J. Baller, A. le Coutre, W. Manglkammer, P.Damman ,B. Ploss, R. Heppelmann............................................................... 111 Hydrothermal PZT Thin Film and its Application to Actuators and Sensors Minoru K. Kurosawa, Takeshi Morita, Takefumi Kanda, Hidehiko Yasui, and Toshiro Higuchi................................................................ 149 Dielectric And Structural Properties And Quasi-One Dimensionality of The BetaineArsenate-Phosphate Mixed Crystal System S. Lanceros-Méndez and G. Schaack, A. Klöperpieper.............................................................................................. 159 The Relation Between Ferroelectric And Magnetic Transitions In A Hexagonal Rbcobr3 Kiyoko Morishita............................................................................................ 209 Part II. Brief Reports Preparation of Tungsten Bronze Structured Ferroelectric ba2nanb5o15 Thin Films and Their Characterizations Shizutoshi Ando and Takeyo Tsukamoto.......................................................... 223 New Mechanism of Molecular Ferroelectricity: Thermo- and Photo-Induced Neutral-Ionic Transformation H. Cailleau, E. Collet, M. Buron-Le Cointe, M.H. Lemee-Cailleau, T. Luty, S. Koshihara, and P. Czarnecki.......................................................... 231 Scanning Force Microscopy Approach: Polarization Phenomena in Ferroelectrics at Nanoscale Alexei Gruverman............................................................................................ 235 Relaxation Time Distribution Function Of Dipole Glass-dradp Jong-Jean Kim, Yun-Seock Choi, and Bog-Gi Kim........................................ 239 Thin Film Growth, Interdiffusion, and Hydrogen-Induced Degradation Phenomena in pb(zrxti1-x)o3 (pzt) and Srbi2ta2O9 (Sbt) Ferroelectric Capacitors A.R. Krauss, O. Auciello, J. Im, A. Dhote, R. Ramesh, and S. Aggarwal.............................................................................................. 243 A Discussion on the Crystal Structures of the pb-Based Complex Perovskites pbfe0.5nb0.5o3 and pbfe0.5ta0.5O3 Nathascia Lampis, Alessandra Geddo Lehmann, and Philippe Sciau........................................................................................... 245 Field Induced Evolution of the Multidomain Microregions in Relaxor (6-8)/65/35 PLZT Ceramics E.L. Rumyantsev and V. Ya. Shur.................................................................... 249 Domain Engineering in Bulk Ferroelectrics V. Ya. Shur..................................................................................................... 253 Study of the Phase Diagram of the sn2p2(s1-xsex)6 Crystal Family Using a Lattice Model G.H.F. van Raaij and T. Janssen...................................................................... 257 Ferroelectricity in Photorefractives Tat’yana R. Volk............................................................................................. 259 Thin Film Effects in the Ferroelectric pbtio3 Kiyotaka Wasa.............................................................................................. 263 Key Word Index……………………………………………………………………..269 Contents of FERROELECTRICS.Vol.1. Frontier in Science and Technology Series. List of Titles. FSRC BOOKS of ABSTRACTS in Science and Technology Conference Series. List of Titles.
An overview of recent developments in the field of first-order phase transitions, which may be considered a continuation of the previous work 'Aggregation Phenomena in Complex Systems', covering work done and discussed since then. Each chapter features a different aspect of the field written by international specialists, and covers such topics as nucleation and crystallization kinetic of silicate glasses, nucleation in concentration gradients, the determination of coefficients of emission of nucleation theory, diamonds from vitreous carbon.
This book deals with the latest achievements in the field of ferroelectric domain engineering and characterization at micro- and nano-scale dimensions and periods. The book collects the results obtained in the last years by world scientific leaders in the field, thus providing a valid and unique overview of the state-of-the-art and also a view to future applications of those engineered and used materials in the field of photonics. The second edition covers the major aspects of ferroelectric domain engineering and combines basic research and latest updated applications such as challenging results by introducing either new as well as extended chapters on Photonics Crystals based on Lithium Niobate and Lithium Tantalate crystals; generation, visualization and controlling of THz radiation; latest achievements on Optical Parametric Oscillators for application in precise spectroscopy. Further more recent advancements in characterization by probe scanning microscopy and optical methods with device and technological orientation. A state-of-the-art report on periodically poled processes and their characterization methods are provided on different materials (LiNbO3, KTP) furnishing update research on ferroelectric crystal by extending materials research and applications.