Ferroelectric Generators Research Articles

An MPMD approach coupling electromagnetic continuum mechanics approximations in ALEGRA

Two complementary approximations for describing aspects of continuum electromagnetics in moving media are discussed: electroquasistatic and magnetoquasistatic. Each has been implemented in the finite element shock code ALEGRA for modeling dynamic electromechanical phenomena on typical engineering time scales, with fully integrated circuit coupling (Niederhaus et al. 2023). The approximations can be obtained by consistent asymptotic balancing of Maxwell’s equations relative to timescales associated with magnetic diffusion, charge relaxation, and electromagnetic wave propagation. In ALEGRA, the electroquasistatic approximation is used for ferroelectric (FE) modeling, while the magnetoquasistatic approximation is used for magnetohydrodynamic (MHD) modeling. In this paper we introduce for the first time a detailed derivation of a useful quasi-steady “low-Rm” variant of the MHD approximation applicable for cases, such as with detonators, where the thermodynamic pressure arising from Joule heating dominates over magnetic forces. An additional purpose of this paper is to present a coupling mode using Multiple Program-Multiple Data (MPMD) message passing communication that allows the user to run 3D FE problems together with 2D and/or 3D MHD problems with the respective simulation domains coupled through a common circuit equation. The MPMD coupling capability is used here to model the dynamic coupling of a notional ferroelectric generator with an RP-87 exploding bridgewire detonator. The simulated bridgewire heats up and bursts under current generated by simulated depoling of the ferroelectric generator, as a demonstration of the MPMD capability.

Modification of both Pr and Td in ZnO-doped 0.97(Bi0.5Na0.5)TiO3-0.03BiAlO3 ferroelectric ceramics

Bi0.5Na0.5TiO3(BNT)-based ferroelectric ceramics demonstrate significant potential for application in high-power ferroelectric generators. However, their practical utilization is hindered by poor thermal stability resulting from a low depolarization temperature (Td). In this work, we simultaneously improve the remnant polarization (Pr) and Td of 0.97BNT-0.03BiAlO3 ceramics via moderate ZnO doping. The effects of ZnO doping on the sintering temperature, ferroelectricity and depolarization behavior of 0.97BNT-0.03BiAlO3 ceramics are systematically studied. The optimum sintering temperature of 0.97BNT-0.03BiAlO3 ceramics decreases from 1140 °C to 1000 °C by approximately 140 °C and the density becomes higher after ZnO doping. At x = 0.01, the phase structure remains R3c rhombohedral phase, and Zn2+ diffuses into the crystal lattices. However, when x ≥ 0.02, the secondary phases ZnO and ZnAl2O4 appear. As the ZnO content increases from x = 0 to x = 0.04, the Pr value shows a continuous increase from 31.13 µC/cm2 to 39.84 µC/cm2, while the Td value initially rises by 32 °C from 156 °C to 188 °C and then decreases to 163 °C. Notably, the highest Td is achieved at x = 0.02, owing to the combined effects of Zn2+ substitution and localized stress between the matrix and the composite. These findings highlight doping ZnO as an effective approach to optimize both Td and Pr of BNT-based materials.

A portable flash x-ray generator powered by an explosive driven ferroelectric generator.

In order to develop a portable flash x-ray source, a compact explosive pulsed power source based on an explosive-driven ferroelectric generator (EDFEG) is investigated numerically and experimentally in this paper. The EDFEG is used as a primary power supply to charge a pulse capacitor, and then the capacitor outputs high current through an inductor and an electrical exploding opening switch (EEOS). Finally, a high voltage fast pulse is generated on a diode, which generates x rays. A circuit model was built to analyze the performance of this compact pulsed power source. A portable flash x-ray generator prototype was constructed in our laboratory. The typical experimental results illustrated that after metal wires of the EEOS exploded, a high-voltage fast pulse with a peak value of 180kV, a rise time of 2.8ns, and a pulse width of 30ns was generated on the x-ray diode. Meanwhile, an x-ray pulse with a pulse width of 19ns, a focus of about 1mm, and a dose of 100 mR at 15cm was obtained.

Suppression of ferroelectric polarization and hence room temperature multiferroicity of LuFeO3 on Cu and Mn doping

Room temperature multiferroicity has been in the centre of interest for last few years due to its enormous potential to be applied as real multifunctional device. LuFeO3 is a potential candidate as room temperature multiferroic1, which offers strong multiferroic coupling at room temperature [1]. Presence of ferroelectric polarization is observed in Mn-doped LuFeO3 also. The main area of restriction is its low polarization, which is to be improved before it can be applied in real devices. In order to do that proper understanding of the mechanism of generation of ferroelectricity is needed. In order to do that we observed that, the ferroelectric and multiferroic properties at room temperature, in orthorhombic distorted perovskite LuFeO3 are greatly affected by Cu or Mn doping. If we replace Fe+3 ion (Ionic Radius=126) with some amount another ion of increasing ionic radius Mn+2 (Ionic Radius=127) and Cu+2 (Ionic Radius = 128) the ferroelectric properties are greatly affected as evidenced by the P-E Hysteresis loop measurements. The appearance of ferroelectricity in LuFeO3 could be attributed to the spin current based model as proposed by katsura et al. [3]. The effect of Cu and Mn doping also can be explained with the Spin current based model [3]. Copyright © 2017 VBRI Press.

A3A'3Zn6Te4O24 (A = Na, A' = Rare Earth) Garnets: A-Site Ordered Noncentrosymmetric Structure, Photoluminescence, and Na-Ion Conductivity.

A large number of oxides that adopt the centrosymmetric (CS) garnet-type structure (space group Ia3̅d) have been widely studied as promising magnetic and host materials. Hitherto, no noncentrosymmetric (NCS) garnet has been reported yet, and a strategy to NCS garnet design is therefore significant for expanding the application scope. Herein, for the series A3A'3Zn6Te4O24 (A = Na, A' = La, Eu, Nd, Y, and Lu), we demonstrated that the structural symmetry evolution from CS Ia3̅d (A' = La) to NCS I4122 (A' = Eu, Nd, Y, and Lu) could be achieved due to the A-site cationic ordering-driven inversion symmetry breaking. Na3A'3Zn6Te4O24 (A' = rare earth) are the first garnets that possess NCS structures with A-site cationic ordering. Diffuse reflectance spectra and theoretic calculations demonstrated that all these NCS garnets are indirect semiconductors. Moreover, their potential applications as host materials for red phosphors and Na-ion conductors were also investigated in detail, which firmly confirmed the NCS structure and A-site cationic ordering. Our findings have paved the way to design NCS or even polar garnets that show intriguing functional properties, such as ferroelectricity, multiferroicity, and second harmonic generation.

Ferroelectric columnar assemblies from the bowl-to-bowl inversion of aromatic cores

Organic ferroelectrics, in which the constituent molecules retain remanent polarization, represent an important topic in condensed-matter science, and their attractive properties, which include lightness, flexibility, and non-toxicity, are of potential use in state-of-the-art ferroelectric devices. However, the mechanisms for the generation of ferroelectricity in such organic compounds remain limited to a few representative concepts, which has hitherto severely hampered progress in this area. Here, we demonstrate that a bowl-to-bowl inversion of a relatively small organic molecule with a bowl-shaped π-aromatic core generates ferroelectric dipole relaxation. The present results thus reveal an unprecedented concept to produce ferroelectricity in small organic molecules, which can be expected to strongly impact materials science.

Flexible ferroelectric wearable devices for medical applications.

SummaryWearable electronics are becoming increasingly important for medical applications as they have revolutionized the way physiological parameters are monitored. Ferroelectric materials show spontaneous polarization below the Curie temperature, which changes with electric field, temperature, and mechanical deformation. Therefore, they have been widely used in sensor and actuator applications. In addition, these materials can be used for conversion of human-body energy into electricity for powering wearable electronics. In this paper, we review the recent advances in flexible ferroelectric materials for wearable human energy harvesting and sensing. To meet the performance requirements for medical applications, the most suitable materials and manufacturing techniques are reviewed. The approaches used to enhance performance and achieve long-term sustainability and multi-functionality by integrating other active sensing mechanisms (e.g. triboelectric and piezoresistive effects) are discussed. Data processing and transmission as well as the contribution of wearable piezoelectric devices in early disease detection and monitoring vital signs are reviewed.

Precise Molecular Design Toward Organic-Inorganic Zinc Chloride ABX3 Ferroelectrics.

Organic-inorganic ABX3 (A, B = cations, X = anion) hybrids with perovskite structure have recently attracted tremendous interest due to their structural tunability and rich functional properties, such as ferroelectricity. However, ABX3 hybrid ferroelectrics with other structures have rarely been reported. Here, we successfully designed an ABX3 hybrid ferroelectric [(CH3)3NCH2F]ZnCl3 with a spontaneous polarization of 4.8 μC/cm2 by the molecular modification of [(CH3)4N]ZnCl3 through hydrogen/halogen substitution. It is the first zinc halide ABX3 ferroelectric, which contains one-dimensional [ZnCl3]-n chains of corner-sharing ZnCl4 tetrahedra, distinct from the anionic framework of corner-sharing or face-sharing BX6 octahedra in the ABX3 perovskites. From zero dimension to one dimension, the high symmetry of ZnCl4 tetrahedra is broken, and all of them align along one direction to form a polar [ZnCl3]-n chain, beneficial to the generation of ferroelectricity. This finding provides an efficient polar anionic framework for enriching the family of hybrid ferroelectrics by assembling with various cations and should inspire further exploration of new classes of organic-inorganic ABX3 ferroelectrics.

Dynamic dielectric properties of the ferroelectric ceramic Pb(Zr0.95Ti0.05)O3 in shock compression under high electrical fields

Shock-induced depolarization of the ferroelectrics could generate a depoling current, which has been utilized widely in the energy conversion devices, such as explosive-driven ferroelectric generators and high pulsed power sources. Among all these ferroelectrics, the lead zirconate/titanate ferroelectric ceramic received most of the attention due to their high energy density and low depolarization pressure, especially Pb(Zr0.95Ti0.05)O3 (PZT 95/5). The dynamic permittivity of PZT 95/5 under the shock compression is critical for their applications, which determines the efficiency of the energy conversion. However, to reveal the dynamic permittivity of the ferroelectrics is challenging, the depolarization process during the shock compression is not only short (∼μs) but also coupled with a high electrical field. In this study, the dynamic permittivity of the PZT 95/5 ceramic in shock compression under high electrical fields has been investigated by using a designed oscillation circuit. The experimental results show that the relative permittivity of PZT 95/5 is about 500 at the initial shock compression, and it is only about 220 after shock transit. This decrease would be explained by the PZT 95/5 phase transition under high pressure. In addition, it is found that the permittivity of poled PZT 95/5 is more sensitive to the electrical field than depoled PZT 95/5, and the damping resistances of poled PZT 95/5 could also be influenced by electric fields.

Harvesting Energy from Human Activity: Ferroelectric Energy Harvesters for Portable, Implantable, and Biomedical Electronics

AbstractEnergy harvesters based on ferroelectric materials, which are capable of converting mechanical and thermal energies into electric power, have drawn unprecedented attention in both academic and industrial fields because of their great potential in harvesting human‐activity‐induced and other energies of the human body to drive low‐power, personal, portable, and implantable electronics. Based on previous works that uncovered the features of advanced materials and the nanotechnologies for the fabrication of ferroelectric generators, we emphasize the potential of ferroelectric energy harvesters in biomedical applications, with not only traditional ferroelectrics but also newly developed ferroelectric biomaterials. In addition, the latest representative integration schemes of hybrid generators with ferroelectric materials are outlined, which could markedly extend the functions of energy harvesters, especially for implantable and biomedical applications.

Impact induced depolarization of ferroelectric materials

We study the large deformation dynamic behavior and the associated nonlinear electro-thermo-mechanical coupling exhibited by ferroelectric materials in adiabatic environments. This is motivated by a ferroelectric generator which involves pulsed power generation by loading the ferroelectric material with a shock, either by impact or a blast. Upon impact, a shock wave travels through the material inducing a ferroelectric to nonpolar phase transition giving rise to a large voltage difference in an open circuit situation or a large current in a closed circuit situation. In the first part of this paper, we provide a general continuum mechanical treatment of the situation assuming a sharp phase boundary that is possibly charged. We derive the governing laws, as well as the driving force acting on the phase boundary. In the second part, we use the derived equations and a particular constitutive relation that describes the ferroelectric to nonpolar phase transition to study a uniaxial plate impact problem. We develop a numerical method where the phase boundary is tracked but other discontinuities are captured using a finite volume method. We compare our results with experimental observations to find good agreement. Specifically, our model reproduces the observed exponential rise of charge as well as the resistance dependent Hugoniot. We conclude with a parameter study that provides detailed insight into various aspects of the problem.

Crystal structure and dielectric/ferroelectric properties of CSD-derived HfO 2 -ZrO 2 solid solution films

Abstract Ultrathin films of HfO 2 -ZrO 2 system, Hf x Zr 1- x O 2 , were fabricated for generating ferroelectric phase. Polycrystalline Hf x Zr 1- x O 2 films were prepared via chemical solution deposition process, in which precursor films consisting of amorphous phase on platinized silicon wafer were crystallized by post-annealing. Metastable orthorhombic phase, recognized as the “ferroelectric” phase, appeared in the Hf x Zr 1- x O 2 films with chemical composition of x = 0.40–0.70 and with film thickness of approximately 40 nm, together with stable monoclinic and/or cubic phases. The dielectric permittivity, e r , and remanent polarization, P r , varied with the chemical composition, meaning that constituent phases of the resulting Hf x Zr 1- x O 2 films dominate their dielectric and ferroelectric properties. Saturated P – E hysteresis loop with P r of 2.1 μC/cm 2 and coercive field of 580 kV/cm was confirmed for the solid solution film of Hf 0.70 Zr 0.30 O 2 ( x = 0.70) at 80 K, whereas no spontaneous polarization was confirmed for pure HfO 2 film ( x = 1.00). These results imply that the orthorhombic phase stabilized by Zr substitution would contribute to the generation of ferroelectricity in HfO 2 -based material consequently.

Dynamic resistivity of Pb(Zr0.95Ti0.05)O3 depolarized ferroelectric under shock wave compression

Explosive-driven ferroelectric generator (EDFEG) has important applications due to its excellent properties of high energy density and small volume. The output of EDFEG is based on the depolarization of ferroelectric during shock wave compression. In a normal mode configuration, a planar shock wave propagates in a direction perpendicular to the polarization axis. If the resulting depolarizing current passes through a large resistive load or a small capacitive load, high electric fields can be produced within the ferroelectric sample. In this case, a portion of the depolarizing charges are lost in the sample due to finite resistivity of shocked ferroelectrics during shock wave transit. But it is very difficult to accurately measure the resistivity of shocked ferroelectric during shock wave compression, due to high pressure and short duration time. In previous studies, the value of the resistivity of shocked Pb(Zr0.95Ti0.05)O3 (PZT95/5) ferroelectric was obtained from the experimental output charge difference for different large resistive loads or by fitting the experimental current histories. However, the current leakage was not observed directly in experiment in the past. Furthermore, the value of the resistivity obtained in each of all these studies was a time-averaged value. In the present work, a new experiment method is developed to investigate dynamic resistivity of PZT95/5 under shock wave compression, in which a pulse capacitor is used as an output load. The current leakage in shocked PZT95/5 is observed in the experiment at a shock stress of 3.5 GPa after the depolarization of all ferroelectrics. This current leakage is just related to the resistance of shocked PZT95/5 and the voltage applied. The experimental results show that the resistivity of shocked PZT95/5 continuously changes in a range of 2.2104 cm-3.5104 cm for time more than the shock transit time of the sample. Based on the experimental results, a dynamic resistance model is established to analyze the resistivity of depolarized PZT95/5 ferroelectric ceramic during shock wave transit in ferroelectric. The simulation results reveal dynamic characteristic of the resistivity of depolarized PZT95/5 ferroelectric ceramic under shock wave compression. The further analysis of experimental results shows that the resistivity continuously changes between 2.0104 cm and 8.0104 cm during shock transit in ferroelectrics. It is believed that dynamic characteristic of the resistivity of shocked PZT95/5 ferroelectric ceramic is related to pressure, electrical field applied and the defects in the material. The dynamic resistivity of shocked PZT95/5 obtained in this paper and its dynamic resistance model will be helpful for designing EDFEGs and their applications in the future.

High Voltage Generation With Transversely Shock-Compressed Ferroelectrics: Breakdown Field on Thickness Dependence

The ability of ferroelectric materials to generate high voltage under shock compression is a fundamental physical effect that makes it possible to create miniature autonomous explosive-driven pulsed power systems. Shock-induced depolarization releases an electric charge at the electrodes of the ferroelectric element, and a high electric potential and a high electric field appear across the element. We performed systematic studies of the electric breakdown field, $E_{b}(d)$ , as a function of the ferroelectric element thickness, $d$ , for Pb(Zr0.95Ti0.05)O3 (PZT 95/5) and Pb(Zr0.52Ti0.48)O3 (PZT 52/48) ceramics compressed by transverse shock waves (shock front propagates perpendicular to the polarization vector) and established a relationship between these two values: $E_{b}(d) = \textrm {const}\cdot d^{-\xi }$ . This law was found to be true in a wide range of ferroelectric element thicknesses from 1 to 50 mm. This result makes it possible to predict ferroelectric generator (FEG) output voltages up to 500 kV and it forms the basis for the design of ultrahigh-voltage FEG systems.

SbSI nanowires for ferroelectric generators operating under shock pressure

Shock-induced electric response of ferroelectric antimony sulfoiodide (SbSI) nanowires is presented for the first time. The sonochemically prepared SbSI nanowires have been aligned in electric field and bonded ultrasonically with Au microelectrodes. Electrical responses of such prepared samples on shock pressure of carbon dioxide have been studied. An impact pressure could be detected, since voltage is created in SbSI due to stress-induced depolarization of ferroelectric. The amplitude of the voltage pulse, generated under shock pressure of 5.9MPa, has reached 29.0(7)V, giving the extremely high electric field 3·107V/m. The response time on pressure impact was shorter than 10µs. The recovery time attained 150(5)µs. The presented SbSI nanodevice is promising for shock pressure detection as well as for application in pulsed power nanogenerators.

Ferroelectric origin in one-dimensional undoped ZnO towards high electromechanical response

Ferroelectricity in ZnO is an unlikely physical phenomenon. Here, we show ferroelectricity in undoped [001] ZnO nanorods due to zinc vacancies. Generation of ferroelectricity in a ZnO nanorod effectively increases its piezoelectricity and turns the ZnO nanorod into an ultrahigh-piezoelectric material. Here using piezoelectric force microscopy (PFM), it is observed that increasing the frequency of the AC excitation electric field decreases the effective d33. Subsequently, the existence of a reversible permanent electric dipole is also found from the P–E hysteresis loop of the ZnO nanorods. Under a high resolution transmission electron microscope (HRTEM), we observe a zinc blende stacking in the wurtzite stacking of a single nanorod along the growth axis. The zinc blende nature of this defect is also supported by the X-ray diffraction (XRD) and Raman spectra. The presence of zinc vacancies in this basal stacking fault modulates p–d hybridization of the ZnO nanorod and produces a magnetic moment through the adjacent oxygen ions. This in turn induces a reversible electric dipole in the non-centrosymmetric nanostructure and is responsible for the ultrahigh-piezoelectric response in these undoped ZnO nanorods. We reveal that this defect engineered ZnO can be considered to be in the competitive class of ultrahigh-piezoelectric nanomaterials for energy harvesting and electromechanical device fabrication.

Integration and Operation of an Electrically Small Magnetic EZ Antenna With a High-Power Standing Wave Oscillator Source

The efficacy of the three-dimensional, rectangular magnetic EZ antenna for use with mesoband high-power microwave (HPM) sources has been demonstrated previously. It overcomes the typical bulky and massive impedance-matching components found currently in most HPM systems, making it an attractive option when space is very limited. However, its extremely compact nature presents practical challenges when dealing with extremely high-power sources due to the associated local field enhancements near the feed and the near-field resonant parasitic element. This letter presents a fully integrated, high-voltage source and radiating system that has several improvements in the antenna, source, and power system that have not before been demonstrated. The full system includes a ferroelectric generator, standing wave oscillator source, and electrically small antenna ( ${\rm ka} = 0.37$ ) operating at 510 MHz that can be packaged inside a 15-cm-diameter tube. This small diameter results in a quarter-wavelength-diameter ground plane, and the effects of this small ground plane on the radiation characteristics are explored. The development of a pressurized radome allows for operation at 73.6 kV, significantly higher than previous studies.

Multiferroic materials and magnetoelectric physics: symmetry, entanglement, excitation, and topology

Multiferroics are those materials with more than one ferroic order, and magnetoelectricity refers to the mutual coupling between magnetism and electricity. The discipline of multiferroicity has never been so highly active as that in the first decade of the twenty-first century, and it has become one of the hottest disciplines of condensed matter physics and materials science. A series of milestones and steady progress in the past decade have enabled our understanding of multiferroic physics substantially comprehensive and profound, which is further pushing forward the research frontier of this exciting area. The availability of more multiferroic materials and improved magnetoelectric performance are approaching to make the applications within reach. While seminal review articles covering the major progress before 2010 are available, an updated review addressing the new achievements since that time becomes imperative. In this review, following a concise outline of the basic knowledge of multiferroicity and magnetoelectricity, we summarize the important research activities on multiferroics, especially magnetoelectricity and related physics in the last six years. We consider not only single-phase multiferroics but also multiferroic heterostructures. We address the physical mechanisms regarding magnetoelectric coupling so that the backbone of this divergent discipline can be highlighted. A series of issues on lattice symmetry, magnetic ordering, ferroelectricity generation, electromagnon excitations, multiferroic domain structure and domain wall dynamics, and interfacial coupling in multiferroic heterostructures, will be revisited in an updated framework of physics. In addition, several emergent phenomena and related physics, including magnetic skyrmions and generic topological structures associated with magnetoelectricity will be discussed.

Electrical Properties of New Hollandite Complex Oxide Nanocrystals

A new class of hollandite Ba-Mn-Ti oxide nanocrystals was synthesized. They are synthetic min- erals exclusively composed of Ba, Ti, Mn, and O elements. The BaMn3Ti4O14.25 nanocrystals (designated BMT-134), a typical member of this newly discovered hollandite oxide group, possess a giant dielectric constant and multiferroic properties. In the present paper, electrical properties of nanocrystals of BMT-134 are studied and compared with BMT-125 (BaMn2TiO14.5). We studied the combined complex impedance and temperature dependent conductivity behaviors. The results prove that electron hopping plays a significant role in the electrical properties of the new hollandite BMT nanocrytals. In addition, the dielectric behavior and generation of ferroelectricity can be interpreted on the basis of Mott polaron theory.

Phase Transition Experimental and Theoretical Study of Micro Power Generator Supplying Source for CMOS Chip Based on Ferroelectric Ceramic Nano-Porous Material.

We demonstrated both experimentally and in theory analysis and calculation that the tin-modified lead zirconate titanate nanoporous ferroelectric generator system can perform as a micro-power supplying source for CMOS chip. The ferroelectric ceramic phase transition under transverse shock wave compression can charge external storage capacitor. The nanoporous microstructure ferro-electric ceramic micro-pulsed-power system is capable of generating low output voltage pulses and supplying CMOS chip with micro power sources. We developed the methodology for theory analysis and experimental operation of the ferroelectric generator. Analysis of the porous ferroelectric ceramic material was carried out by X-ray diffractometry and X-ray photoelectron spectroscopy. Microstructures and surface morphology of porous ferroelectric ceramics samples were examined by using scanning electron microscopy. The planar shock wave experiments were conducted on a compressed-gas gun. The experimental results were in good agreement with the theory analysis. Keywords: PSZT Ferroelectric Ceramic, Shock Wave, Phase Transition, Depolarization, Micro-Power-Generator.