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State-of-the-Art and Perspectives for Electroactive Polymers
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Adil A. Gobouri, Electroactive Polymeric Materials, 2022
Rita Martins, Parastou Sadeghi, Ana P.M. Tavares, Goreti Sales
Ferroelectricity is a property associated with spontaneous electric polarization that occurs in a non-conducting crystal or dielectric material. Polymers with ferroelectric behavior are called ferroelectric polymers, typified by a change in the spontaneous/reversible polarization of the material, under exposure to an external electric field (Bar-Cohen and Anderson, 2019; Kim and Tadokoro, 2007; Qian et al., 2015; Bar-Cohen et al., 2017; Katsouras et al., 2016). Besides ferroelectricity, ferroelectric materials can exhibit a piezoelectric and pyroelectric behavior, in which it can convert mechanical vibrations or thermal fluctuations into electrical energy, respectively (Bar-Cohen et al., 2017). Although ferroelectrics are termed with the prefix ferro which means iron (Fe), these materials do not contain iron atoms in their chemical structure. However, they exhibit analogous characteristics to ferromagnetics, and therefore, the origin of the name ferroelectric (Li and Wang, 2016; Huang and Scott, 2018).
Electrical characterization of electro-Ceramics
Published in Amit Sachdeva, Pramod Kumar Singh, Hee Woo Rhee, Composite Materials, 2021
Various dielectric and non-conducting materials exhibit spontaneous electric polarization without an external applied field; this is called ferroelectricity. The name ferroelectricity is analogous to its magnetic counterpart, ferromagnetism [2]. Ferroelectricity [3–5] was initially discovered in Rochelle salt (double tartrate of sodium and potassium; sodium potassium tartrate tetrahydrate; (KNaC4H4O6.4H2O) in 1921 by Joseph Valasek. Rochelle salt was the first crystal to be designated as a ferroelectric material, having two Curie temperatures, 297 K and 255 K. This salt shows a ferroelectric property with monoclinic symmetry at temperatures below 255K and above 297K but orthorhombic symmetry between 255 K and 297 K. According to Czech scientist Roger Valasek, electric displacement in one direction in the ferroelectric material depends on the previous values of the electric field, E, but if the electric field increases steadily up to a maximum value and then starts to decrease to reach the maximum value in the opposite direction, electric displacement traces a hysteresis loop. The ferroelectric material’s hysteresis loop traced between applied electric fields resembles the ferromagnetic hysteresis loop traced between an applied magnetic field and magnetic induction, although it has no connection with iron (ferrum). It is this analogy with ferromagnetism that gives ferroelectricity its name. “Siegnett-electricity,” an earlier name derived from its first discovery in Rochelle salt (Siegnett salt), and was introduced by Kurchatov (1933).
Multiferroic Polymer Film Composites for Memory Application
Published in Alexander V. Vakhrushev, Omari V. Mukbaniani, Heru Susanto, Chemical Technology and Informatics in Chemistry with Applications, 2019
Rehana P. Ummer, Nandakumar Kalarikkal
The most promising and most studied material for memory devices is bismuth ferrite, BFO which shows room temperature ferroelectricity (Tc ≈ 1100 K) and antiferromagnetism (TN ≈ 640 K). The material has a rhombohedral structure and shows a large ferroelectric polarization15 with spontaneous polarization Ps vector along (111) axis and significant ME coupling.16 Owing to its large spontaneous polarization, possibly the largest among all known perovskite and nonperovskite multiferroic oxides, BFO is also a prospective candidate for next-generation ferroelectric memory applications. However, the major challenges BFO faces in this context is its poor leakage characteristics, the tendency to fatigue17 and thermal decomposition near coercive field.18
Developing a Piezoelectric Generator for Military Equipment – A Feasibility Study
Published in Electric Power Components and Systems, 2023
Karthikeyan Sathasivam, Ilhan Garip, Hayder Sharif, Jamal K. Abbas, Ali Adhab Hussein, Shahad K. Khaleel, Mustafa Asaad Rasol
Unlike crystals, piezoelectric ceramics do not have a crystalline structure but a set of domains, which all have the same molecular constitution. The molecules aggregate according to their different polarities, resulting in parts whose polarities are oriented in many different directions. Even when deformed, the ceramic does not demonstrate a dipolar moment. For a ceramic to obtain multiple piezoelectric properties, it is necessary to orient the polarities of these domains in one main direction: the process [16]. These ceramics have the property of ferroelectricity. Ferroelectricity refers to the ability to change the polarity of a material by applying an external electric field. When ceramics are at a temperature equal to or above the Curie temperature, they undergo rearrangements in their molecular structure, becoming paraelectric, that is, without polarity. The process of polarization of ceramics involves placing them under a very high voltage electric field and heating and cooling them, forcing the rearrangement of their molecules, which become polarized due to their ferroelectric behavior below the Curie temperature. When the ceramic is at rest, it presents a particular dipolar motion due to its polarity [17]. When the battery’s terminals are connected to an electrical circuit, the electrons move so as to cancel the power difference between the terminals. Similarly, to the quartz crystal, when the ceramic moves in the direction of its polarity, its dipole moment varies, resulting in the generation of electric current. Figure 3 shows the Phases of PVDF.
Ferroelectric, Piezoelectric Mechanism and Applications
Published in Journal of Asian Ceramic Societies, 2022
Arun Singh, Shagun Monga, Neeraj Sharma, K Sreenivas, Ram S. Katiyar
Materials exhibiting ferroelectricity are those polar dielectrics which when subjected to an external electric field reverse and reorient their spontaneous polarization. An organic pyroelectric crystal will be a ferroelectric if it satisfies the structural conditions that no atom within the unit cell can be displaced by more than about 1 Å from the position that it would occupy in the non-ferroelectric phase and that the displacement is greater than about 0.1 Å [4]. The first report on ferroelectricity was first published on Rochelle salt in 1921; the second was on KDP in 1935, and after that on BaTiO3 in 1944. Since then, there has been a steady addition to this list, and at present, there are over 200 materials known to show ferroelectricity [5]. Initially, the name ferroelectric was not common, and this phenomenon was known as Seignette electricity.
A detailed study of hydrogen bonded ferroelectric mesogens formed between alkyl and alkyloxy benzoic acids with carbamyl glutamic acid
Published in Liquid Crystals, 2018
G. Sangameswari, N. Pongali Sathya Prabu, M. L. N. Madhu Mohan
Liquid Crystals (LCs) are one of the vital chemical components [1] adopted in designing the display devices [2] in this modern era. Investigation of various parameters such as physical [3], chemical [1], thermal [4], mechanical [5], electrical [6], dielectrical [7] and optical [8] properties of the formed LC suits them best for the application utility. Exhibition of the wide thermal mesogenic range and response to the external parameters are expected as the outcomes of the designed LC. Hydrogen-bonded liquid crystals (HBLCs) satisfy these objectives which can be concluded from the strong review of literature available in the past decades [9–13]. Ferroelectricity is a special phenomenon exhibited by the materials, viz. possessing spontaneous polarisation even in the absence of applied electric field and the reorientation happens by the application of external stimulus [14]. This property enables the increased microsecond speed which makes the material as the best optical switchable display device [15]. Hydrogen-bonded ferroelectric liquid crystals (HBFLCs) are formed when the chemical components possess chiral carbon [16,17]. High spontaneous polarisation, optimum magnitude of helical pitch length, optical and dielectric anisotropy, viscosity and tilt angle are the parameters that are effected by the ferroelectricity. Meyer is the first researcher to explain the ferroelectricity phenomenon exhibited in the chiral smectic LC system in 1975 [18]. A new class of LC [19–21] named as bent core LCs or banana LCs gained importance in the recent years. In this type of LC, even though chiral carbon is not a mandatory requirement, still it exhibits ferroelectricity with new nomenclature of phases and hence is also referred as achiral LCs.