Technology & Engineering
Ferroelectricity
Ferroelectricity is a property exhibited by certain materials where they can retain a spontaneous electric polarization even in the absence of an external electric field. This polarization can be reversed by applying an external electric field, making ferroelectric materials useful for applications in memory devices, sensors, actuators, and capacitors. The unique properties of ferroelectric materials make them valuable in various technological advancements.
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10 Key excerpts on "Ferroelectricity"
eBook - PDF- Rajendra Prasad(Author)
- 2013(Publication Date)
- CRC Press(Publisher)
339 © 2008 Taylor & Francis Group, LLC 16 Ferroelectric and Multiferroic Materials 16.1 Introduction There has been much excitement during the last decade regarding ferro-electric and multiferroic materials because of their interesting properties that can be controlled by the application of electric or magnetic fields. Ferroelectric materials are insulating materials that can exist in two or more stable polarization states. They have spontaneous polarization that can be reversed by the application of an electric field. Out of 32 point groups, only 10 groups with a unique polar axis can demonstrate spontaneous polariza-tion. Above a certain temperature, known as the ferroelectric Curie tempera-ture, the material loses spontaneous polarization and becomes paraelectric. In general, at Curie temperature, there is a structural change signaling a first-order phase transition, although there are some exceptions. Owing to their interesting properties, ferroelectric materials find applications in various devices such as transducers, actuators, and nonvolatile ferroelectric memories. Multiferroic materials exhibit at least two out of three properties in the same phase, the properties being Ferroelectricity, ferromagnetism or some magnetic order, and ferroelasticity. In this chapter, we shall focus on materials that have magnetic order and Ferroelectricity. These materi-als are exciting because one can control their properties by applying an electric or magnetic field. However, the number of such known materials is very small and now an intense research by several groups is going on to find such materials that may find applications in future devices and technologies. Spontaneous polarization is an important feature of these materials. Therefore, we begin with how to calculate polarization in insulating materi-als using a first-principles approach in Section 16.2.
eBook - PDF- Tariq Altalhi, Mohammad Abu Jafar Mazumder(Authors)
- 2024(Publication Date)
- Wiley(Publisher)
This information is necessary for optimizing their performance and developing new applications. 116 Ferroic Materials-Based Technologies 5.5 Applications of Ferroelectric and Ferroelastoelectric Materials Smart materials are designed to respond to external stimuli, such as tem- perature or electric fields. Ferroelectric and ferroelastoelectric materials have been identified as promising candidates for developing smart mate- rials due to their unique properties that allow them to change in response to external forces or fields. Ferroelectric materials possess the remarkable quality needed to sustain smart material application. The reversible alter- ation of polarization towards electric fields grants flexibility regarding shape, stiffness, or optical properties. Notably, piezoelectric actuators stand as the most frequent implementation of ferroelectric components by ener- gizing electrical output into mechanical input with various uses such as micro- and nano-positioning, vibration control mechanisms, and robotic systems. Further usage presents itself with the utilization of Ferroelectricity by serving as sensors transforming thermal or mechanical energy into an electric signal; pressure sensors or temperature detectors for industry or medicine are among these applications. Moreover, their non-volatile mem- ory potential offers superior storage performance retaining important data regardless of whether power is off. Ferroelectric materials’ unique proper- ties render them ideal for various applications like digital cameras, mobile phones, and portable music players due to their versatility and ease of use. These compounds are equally effective within optical devices where they promptly change their refractive index following electrical fields, which effectively regulates light intensity in fiber-optic networks using variable optical attenuators.
eBook - PDF- Husein Irzaman(Author)
- 2018(Publication Date)
- IntechOpen(Publisher)
Section 1 Ferroelectricity Chapter 1 Introductory Chapter: Ferroelectrics Material and Their Applications Irzaman Husein and Renan Prasta Jenie Additional information is available at the end of the chapter http://dx.doi.org/10.5772/intechopen.80643 1. Ferroelectrics material Ferroelectricity is a symptom of inevitable electrical polarisation changes in materials without external electric field interference. Ferroelectricity is a phenomenon exhibited by crystals with a spontaneous polarisation and hysteresis effects associated with dielectric changes when an electric field is given. Our fascination with Ferroelectricity is thanks to a beautiful article by Itskovsky, in which he explains about kinetics of a ferroelectric phase transition in thin ferro -electric layer (film) [ 1 ]. We have been researching about ferroelectrics materials since 2001 [2, 3 ]. There are several materials known for its ferroelectric properties. Barium titanate and barium strontium titanate are the most well known [2 –4 ]. Several others include tantalum oxide, lead zirconium titanate, gallium nitride, lithium tantalate, aluminium, copper oxide and lithium niobate [ 5–14 ]. Researchers often introduce dopant to enhance material’s ferroelectric characteristics. Lanthanum is one of the most well-known materials to be used as dopant [10, 13 , 15–18 ]. Ferric oxide is also most often used as dopant [ 8 , 19– 21]. Other dopants include gallium oxide, tantalum oxide, niobium oxide and manganese [ 9 , 14 , 19 , 22 – 24]. Furthermore, we are cur -rently trying to enhance the ferroelectric effects using photonic crystals [25]. When researchers are growing ferroelectric thin films, they have used various concentrations, starting from 0.25 to 2.5 mole [ 7 , 23, 25 – 28]. Researchers applied the chemical solutions of vari -ous substrates: the most often is p-type silicone [ 3 , 11 ].
eBook - PDFAdvanced Structural Chemistry
Tailoring Properties of Inorganic Materials and their Applications
- Rong Cao(Author)
- 2021(Publication Date)
- Wiley-VCH(Publisher)
Solid-state phase transitions are well charac-terized by structural transformations between different phases under external field, such as temperature and pressure. During the phase transition, a series of physical properties will show significant changes, resulting in a variety of multifunctional materials. Consequently, structural phase transitions are potentials for the gener-ation and evolution of many physical/chemical properties in solid materials, such as Ferroelectricity and spin transitions (or spin crossings). Ferroelectric material usually has two or more possible orientations of spontaneous polarization, whose orientation can be changed under the action of electric field. The core issue for ferroelectric research is the spontaneous polarization that behaves as a kind of polar vector. The appearance of spontaneous polarization creates a special direction Advanced Structural Chemistry: Tailoring Properties of Inorganic Materials and their Applications, First Edition. Edited by Rong Cao. © 2021 WILEY-VCH GmbH. Published 2021 by WILEY-VCH GmbH. 602 11 Relationship Between Structure and Ferroelectric Properties inside the crystal materials. Structurally, the configuration of atoms in each unit cell causes the positive and negative charges to be displaced relative to each other in this direction, forming the entire electric dipole moments. The crystal exhibits polarity in this direction, with one end being positive and one end being negative. Therefore, this direction is not symmetrically equivalent to any other direction of the crystal and is called a special polar direction. However, the Ferroelectricity usually exists only in a certain temperature range. When the temperature exceeds a certain value (namely, T c ), the spontaneous polarization disappears and the material becomes a paraelectric.
eBook - PDFHandbook of Nanophysics
Nanoparticles and Quantum Dots
- Klaus D. Sattler(Author)
- 2016(Publication Date)
- CRC Press(Publisher)
3 -1 3.1 Introduction From their discovery, ferroelectrics were more of academic interest, of little application and theoretical relevance. The recognition of the relationship between lattice dynamics and Ferroelectricity as well as the modeling of ferroelectric phase transitions has intensified the investigations of ferroelectrics. The focus changed further, when thin-fi lm ferroelectrics were developed and applied in different devices in 1980s. Since that time, there has been a renewed effort in the fabrication, appli-cation, and theoretical understanding of ferroelectric materials scaled down up to nanometers. This chapter reviews the physical behavior of such ferroelectric nanoparticles. 3.1.1 Ferroelectric Properties The main properties of ferroelectrics in bulk material (Blinc and Zeks 1974, Lines and Glass 2004, Strukov and Levanyuk 1998) are summarized in this section. The appearance of multistable degenerated states with spontaneous macroscopic polarization P = σ s below a critical temperature T c , which can be switched by an electric field, is the general feature of Ferroelectricity. The sys-tem is paraelectric above the phase transition temperature. The system can undergo a first- or a second-order phase transition. In the first case, the polarization, as the order parameter of the sys-tem, exhibits a discontinuous change from the paraelectric to the ferroelectric phase. A second-order transition is characterized by a continuous change of the polarization. Most ferroelectric materials reveal a first-order transition near to a second-order one which is characterized by a small jump in the polarization as well as a drastic increase of the corresponding dielectric sus-ceptibility ε ( T ). The transition is often masked by intrinsic fields, depolarization effects, and defects. This chapter is not focused on the behavior in the immediate vicinity of the phase transi-tion.
eBook - PDF- Batra, Ashok K., Alomari, Almuatasim(Authors)
- 2017(Publication Date)
Such characteristics (shown in Fig. 2.3) enable technological applications across a wide range of sectors, including electronics, construction, transportation, agriculture, food and packaging, health care, 25 Fundamentals of Ferroelectric Materials sports and leisure, household appliances, energy and the environment, space, and defense. 2.5 Pyroelectric Phenomenon The pyroelectric effect, or pyroelectricity, refers to a change in the internal polarization of a material due to small changes in temperature, producing a flow of charges to and from the material ’ s surface. Pyroelectric materials are dielectric materials and possess a spontaneous electrical polarization that appears in the absence of an applied electrical field or stress. Of the 20 noncentrosymmetric crystal classes, ten contain a unique polar axis under unstrained conditions, which implies that such crystals are already spontaneously polarized in a certain temperature range. Thus, they exhibit both piezoelectric and pyroelectric effects. Pyroelectricity is a coupled effect that corresponds to a change in temperature with a change in the electrical displacement D (C/m 2 ), as shown in Fig 2.3. There are two contributions to the pyroelectric effect that are represented by dashed lines. The first contribution is the primary pyroelectric effect caused by a change in temperature, which leads to a change in the electric displacement in a crystal rigidly clamped under constant strain s to prevent expansion or contraction. The primary pyroelectric effect signifies direct coupling between polarization and temperature. The second contribution is the secondary pyroelectric effect that results from crystal deformation, i.e., thermal expansion caused by a temperature change, leading to strain from the piezoelectric process that alters the electric displacement. In short, temperature variation leads to a change in thermal expansion, which leads to a change in the electrical displacement.
- Mike Golio, Janet Golio, Mike Golio, Janet Golio(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
Among the properties that are discussed are hysteresis and domains. Ferroelectric and piezoelectric materials derive their properties from a combination of structural and electrical properties. As the name implies, both types of materials have electric attributes. A large number of materials which are ferroelectric are also piezoelectric. However, the converse is not true. Pyroelectricity (heat to electric field conversion) is closely related to ferroelectric and piezoelectric properties via the symmetry properties of the crystals. Examples of the classes of materials that are technologically important are given in Table 28.1. It is apparent that many materials exhibit electric phenomena which can be attributed to ferroelectric, piezoelectric, and electret behavior. It is also clear that vastly different materials (organic and inorganic) can exhibit Ferroelectricity or piezoelectricity, and many have actually been commercially exploited for these properties. As shown in Table 28.1, there are two dominant classes of ferroelectric materials, ceramics and organics. Both classes have important applications of their piezoelectric properties. To exploit the ferroelectric 28 -1 28 -2 RF and Microwave Passive and Active Technologies TABLE 28.1 Ferroelectric, Piezoelectric, and Electrostrictive Materials Type Material Class Example Applications Electret Organic Waxes No recent Electret Organic Fluorine based Microphones Ferroelectric Organic PVF2 No known Ferroelectric Organic Liquid crystals Displays Ferroelectric Ceramic PZT thin film NV-memory Piezoelectric Organic PVF2 Transducer Piezoelectric Ceramic PZT Transducer Piezoelectric Ceramic PLZT Optical Piezoelectric Single crystal Quartz Freq.
eBook - PDFModern Materials
Advances in Development and Applications
- Henry H. Hausner(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
(29). Here we would apply an electric field and observe displacement. BaTi0 3 ceramics have been used as drivers for ultra-sonic cutters, as resonant elements in oscillating circuits, and in other sonic generating equipment. To see why the ferroelectric property is important, consider an or-dinary piezoelectric material formed as a polycrystalline solid or ceramic. If a field were to be applied in the x-direction with zero mechanical stress, as an example, then the y longitudinal strain, x 2 , would be given by X2 = duEi An important measure of the effectiveness of a piezoelectric as a transducer is the electromechanical coupling coefficient, k, whose square is defined as the ratio of energy stored in mechanical form to the total input electrical energy. It is recognized that x 2 can be an elongation or a compression, depending on the direction of the electric field with respect to the polar direction which is fixed in each single crystal by the actual orientation of what we may term the piezoelectric axis. Since the crystallites of which a polycrystalline material is composed are, in general, oriented at random, there would be as many that would con-tract as would expand. The net effect under these conditions would be an apparent absence of the piezoelectric effect. More generally, a ran-domly oriented polycrystalline material behaves as if it were isotropic because of this averaging of physical properties over all directions. When produced, a ferroelectric ceramic is a polycrystalline solid with individual crystallites randomly oriented. The important difference between these materials and other polycrystalline piezoelectric bodies is that it is possible to align the piezoelectric axes of the small single crystals of which the ceramic is composed.
eBook - PDFFerroelectrics
Physical Effects
- Mickaël Lallart(Author)
- 2011(Publication Date)
- IntechOpen(Publisher)
Since that time, considerable development and progress have been made on both materials and devices based on PVDF. This work helped establish the field of ferroelectric polymer science and engineering [Nalwa, 1995a]. There are many novel ferroelectric polymers, such as poly(vinylidene fluoride) (PVDF) copolymers, poly(vinylidene cyanide) copolymers, odd-numbered nylons, polyureas, ferroelectric liquid crystal polymers and polymer composites of organic and inorganic piezoelectric ceramics [Nalwa, 1991 and Kepler & Anderson, 1992 as cited in Nalwa, 1995b; Nalwa, 1995a]. Among them, PVDF, and its copolymers are the most developed and promising ferroelectric polymers because of their high spontaneous polarization and chemical stability. Ferroelectricity is caused by the dipoles in crystalline or polycrystalline materials that spontaneously polarize and align with an external electric field. The polarization of the dipoles can be switched to the opposite direction with the reversal of the electric field. Similar to inorganic ferroelectric materials such as PbZr 0.5 Ti 0.5 O 3 (PZT) and SrBi 2 Ta 2 O 9 (SBT), organic ferroelectric materials exhibit ferroelectric characteristics such as Curie temperature (the transition temperature from ferroelectrics to paraelectrics), coercive field (the minimum electric field to reverse the spontaneous polarization) and remanent polarization (the restored polarization after removing the electric field). However, the low temperature and low fabrication cost of organic ferroelectric materials enable them to be used in a large number of applications, such as flexible electronics. In this chapter, the discussion is focused on poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)], one of the most promising PVDF ferroelectric copolymers. The main objective of this chapter is to describe the ferroelectric properties of P(VDF-TrFE) copolymer and review the current research status of ferroelectric devices based on this material.
eBook - PDFFerroelectric Materials
Synthesis and Characterization
- Aime Pelaiz Barranco(Author)
- 2015(Publication Date)
- IntechOpen(Publisher)
Ferroelectric materials, good isolators by their nature, exhibit temperature-dependent polari‐ zation, i.e., when the sample is heated the polarization changes and an electrical current is produced (pyroelectric current) which disappears at a certain temperature [ 1 ]. For normal ferroelectrics, the pyroelectric current ( i P ) achieves a maximum value when the temperature ( T ) increases, and then decreases until zero at the ferroelectric-paraelectric phase transition temperature. For relaxor ferroelectrics, the pyroelectric current is different from zero even at higher temperatures than T m , as well as the temperature of the corresponding maximum for the real part of the dielectric permittivity [27]. However, the study of the pyroelectric behaviour and its corresponding physical parameters may be quite difficult in many ferroelectric systems because, apart from the localized dipolar species, free charges can also exist in the material. The decay of the electrical polarization could be due to dipolar reorientation, the motion of the real charges stored in the material and its ohmic conductivity. The first of these is induced by thermal excitation, which leads to decay of the resultant dipole polarization, and the second is related to the drift of the charges stored in the internal field of the system and their thermal diffusion. During the temperature rise, the dipoles tend to be disordered gradually owing to the increasing thermal motion, and the space charges trapped at different depths are gradually set free. Therefore the pyroelectric behaviour is usually overlapped by other thermally stimulated processes, and a detailed analysis of this Ferroelectric Materials – Synthesis and Characterization 88 phenomenon is very important in order to separate the different components of the electrical current during the heating of the material ( i-T dependences), to then make a real pyroelectric characterization of any system.
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