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When a PhD student called Joseph Valasek discovered ferroelectricity exactly 100 years ago, few people realized the enormous impact it would have on science and technology. Amar S Bhalla and Avadh Saxena pick their favourite applications of this fundamental physics phenomenon

The year 2020 marks hundred years since the watershed discovery of the phenomenon of ferroelectricity although at that time its importance was hardly realized. We provide a historical account of th...

In this study, (1-x)BaZr0.2Ti0.8O3-(x)(Ba0.7Ca0.3)0.985La0.01TiO3 ((1-x)BZT-(x)BCLT) ceramics, where x = 0.3, 0.4, 0.5, and 0.6, were prepared employing a conventional solid-state sintering technique. X-ray diffraction patterns and dielectric measurements indicated three phase regions at room temperature, including a single rhombohedral (x = 0.3), a phase coexistence of rhombohedral and tetragonal (x = 0.4), and a single tetragonal structure (x ≥ 0.5). X-ray photoemission spectra at the surface of ceramics confirmed the oxidation state of Ba2+, Ca2+, Ti4+, and Zr4+ ions. Upon BCLT addition, the reduction of the average grain size and the presence of the tetragonal structure significantly affected the dielectric, ferroelectric, and piezoelectric properties of these ceramics. With these results, the composition x = 0.3 showed maximum er′ and em′, whereas the composition x = 0.5 showed maximum Pr, Ec, d33, kp, and d∗33 factors. These results suggest a new phase diagram for the (1-x)BZT-(x)BCLT system, which could be tuneable by BCLT concentration and might be useful as an alternative material in dielectric, ferroelectric, and piezoelectric devices.

Made available in DSpace on 2019-10-06T15:53:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Ceramic composites based on Pb(Zr,Ti)O3/NiFe2O4 (PZT–NFO) have been synthesized from the conventional solid-state reaction method. The ferroelectric and magnetic properties have been investigated at room temperature. The obtained results revealed excellent characteristics of both ferroic responses, which suggest the studied ceramic composite as a promising material for practical applications in magneto-electric related devices. Grupo de Ferroelétricos e Materiais Multifuncionais Instituto de Física Universidade Federal de Uberlândia Departamento de Física e Química UNESP Instituto Federal de Educação Ciência e Tecnologia do Triangulo Mineiro Departamento de Física Universidade Federal de São Carlos Inamori School of Engineering Alfred University Multifunctional Electronic Materials and Devices Research Lab Department of Electrical and Computer Engineering College of Engineering The University of Texas at San Antonio Departamento de Física e Química UNESP

In this work, we have studied the microscopic, ferroelectric, magnetic and microstructural characteristics of cobalt ferrite/barium titanate core–shell magnetoelectric nanocomposites. Magnetoelectr...

An atomistic field theory was introduced to study the electromechanical response in a ferroelectric perovskite at nanoscale. Based on a shell model potential, the polarization switching pro...

The dynamic modulation of effective electro-optic (EO) coefficient in pulsed laser deposited SBN thin film was investigated using Senarmont Compensation method. Prism coupling technique was used to realize a waveguide to guide the light in SBN thin film. The dynamic variation of effective electro-optic coefficient over a wide frequency range (10 Hz–20 MHz) was investigated with the maximum value of 198 pm/V. This wide frequency bandwidth obtained in the present article opens up avenues to design an EO modulator using ferroelectric SBN thin film. A lower value of half wave voltage (38 V) along with high figure of merit ( 0.9 × 10 6 V 2 ) were obtained for the fabricated SBN60 thin film based EO modulator.

The structural, dielectric, ferroelectric, and ferromagnetic properties of multiferroic ceramics (1–x)Ba(Zr0.2Ti0.8)O3-xBa0.7Ca0.3FeTaO5 (abbreviated as (1–x)BZT-xBCFT where x = 0.2, 0.25, ...

(Ba0.7Ca0.3)Ti1-xCuxO3-x ceramics (where x = 0, 0.01, 0.02 and 0.03) were prepared employing a conventional solid state sintering technique. X-ray diffraction patterns and Ti K-edge X-ray Absorption Near-Edge Structure (XANES) spectra indicated a structural distortion of Cu-doped ceramics. Depending on Cu content, the features of normal ferroelectric and diffuse dielectric phase transition could be induced by the Cu addition. The temperature where maximum dielectric existed was decreased upon increase of Cu concentration. The creation of oxygen vacancies and defect dipoles caused double-like P-E loop in host material. The decrease of d33, g33 and kp values was observed in correlation with decrease of Pr in doped ceramics. The results here suggested that the electrical properties of this ceramic system may be largely tunable by Cu dopant and could be an attractive material for high-dielectric response devices.

Electro-optic (EO) devices with high EO coefficients at radio and microwave frequencies are integral components of the photonics industry. This work determines the EO effect of ferroelectric Li-doped niobium-rich potassium tantalate niobate (K 0.95 Li 0.05 Ta 1- x Nb x O 3 ; KLTN) single crystals using improved dynamic EO measurement. The phase transitions of KLTN crystals were investigated via variable-temperature Raman spectroscopy. A full view of the surface displacement and velocity for the KLTN sample at the resonant frequency was studied using an ultra-frequency vibrometer. The KLTN sample with x = 0.60 exhibits the enhanced effective EO coefficient (γ c ) ∼ 217 pm/V near the piezoelectric resonant peaks, which is comparable with the value at low frequency. The piezoelectric enhanced EO property of KLTN single crystals can be attributed to nonlinear polarization and nonzero stress, and showing promising for designing practical optical-piezoelectric-mechanism coupling devices.

Co-existent ferroelectric and magnetic ordering at room temperature in multiferroics has generated significant interest for potential applications in low-power sensors, transducers, and memory devices. Despite tremendous efforts centered on site-substitution in BiFeO3 to attain enhanced functionality, local probing of multiferroic domain dynamics with dopant concentration remains overlooked. Here we report a detailed investigation on ferroelectric and magnetic domain mapping of Bi1−XCeXFeO3; 0 ≤ X ≤ 0.2 (BCFOX) thin films and discussed concentration-dependent behavior of piezo-response switching, piezo-actuation butterfly-loop and phase-hysteresis, and magneto-dielectric coupling. Large piezo-response amplitude change of 30 mV and near to complete phase reversal of ~150° together with homogeneous magnetic domain distribution and an enhanced magneto-dielectric coupling coefficient of 2.15% at 0.3 T unveils improved ferroelectric ordering in polycrystalline BCFO0.12 thin film. We believe, our findings will develop a comprehensive understanding of sensitive force microscopy technique for the custom-made advancement of BiFeO3 based multiferroic family.

Bioactive ferroelectric composites based on polyvinylidene fluoride, hydroxyapatite and β-tricalcium phosphate have been synthesized and their structural, microstructural, bioactive, and ferroelectric properties are characterized. Structural and FTIR investigations showed the presence of the polar polyvinylidene fluoride (β2) phase, while ferroelectric characterizations revealed remnant polarizations and coercive field, around 0.04 μC/cm2 and 28 kV/cm, respectively, for these biocompatible samples. Structural and microstructural analysis of samples previously immersed in simulated body fluid for 7 days revealed a large apatite phase growth (1.45 μm) on the composites' surfaces as a strong indication of their elevated bioactivity and potentialities for bone tissue engineering.

Nanoscale ferroelectric behaviour has been investigated in epitaxial BaZrO3 thin films grown in an oxygen deficient environment. Though centrosymmetric in nature, prominent ferroelectric polar states were observed via Piezo Force Microscopy (PFM), with polarization switching achieved when oppositely poled. Absence of intrinsic polar directions annul the conventional root causes for ferroelectricity like structural asymmetry and strain, rather attributes the nanoscale polar orders observed, to defect dipoles originated from oxygen vacancies introduced during the film growth. Electrostatic Force Microscopy (EFM) exhibiting inhomogeneous distribution of surface potential confirms the accumulation of oxygen vacancies contributing towards the measured polarizations.

(Ba0.7Ca0.3)TiO3, (Ba0.7Ca0.3)0.995Ti0.99Nb0.01O3 and (Ba0.7Ca0.3)Ti0.99Mg0.01O2.99 ceramics were prepared employing a solid state sintering method. The presence of Ti4+ and structural changes were revealed by X-ray diffraction patterns and X-ray absorption spectra. Upon substitution of Nb5+ and Mg2+ ions, a decrease of the ferroelectric transition temperature near room temperature and relaxor-like features of the dielectric properties were observed in correlation with decreased tetragonality. The change in phase transition temperature affected significantly piezoelectricity and ferroelectricity of doped ceramics. The doping could enhance the dielectric properties near room temperature of BCT ceramic. The results here suggest that dielectric, piezoelectric and ferroelectric properties of BCT may be largely tunable by Nb and Mg dopants, and BCT could be an alternative material for ferroelectric devices.

Dielectric properties of (Sr0.7Pb0.3)TiO3 ceramics were investigated up to 100 kHz down to −260 °C along with temperature dependent thermal strain, X-ray diffraction peaks, and hysteresis loops. The (Sr0.7Pb0.3)TiO3 ceramic showed almost frequency independent relative dielectric permittivity, the Curie point at 10 °C from the cubic to the tetragonal, and dielectric maxima with the second-order phase transition, more than 30000. The Curie-Weiss behavior showed deviation near the Curie point owing to microscopic polarization similarly observed in relaxor ferroelectrics. Loss tangent measurements showed low values in the paraelectric phase, less than 0.0005, and three anomalies in the ferroelectric phase.

In this contribution, a promising environmentally friendly lead-free ferroelectric/polymer 0-3 composite, using polyvinylidene fluoride and barium sodium titanate niobate compounds, was synthesized and structurally and dielectrically characterized. The results suggest the complete formation of a 0-3 connected composite with enhanced dielectric properties, reaching a relative permittivity of 32 and a dissipation loss of 4%, at 1 kHz and 300 K, respectively. These dielectric features are associated with the intimate contact between the polymer and ceramic fraction in the composite that lead to the increase of the polar β-phase amount in the polymer fraction, at room temperature.

Targeted drug delivery has been the focus of medical millimeter and nanometer sized-robots along with its other biomedical applications. Magneto-electric (ME) robots uses the coupling of the magnetostrictive and piezoelectric properties to generate electric pulses. A CFO-BTO (Cobalt Iron Oxide and Barium Titanate), ferromagnetic core and ferroelectric shell is modelled using COMSOL Multiphysics simulation of 2.5mm and 5mm spherical radius that produced an electric pulse of 0.625µV of 8.33ms time scale when exposed to an external magnetic field of intensity 50 Oe at 60Hz. The ME can be externally controlled via a magnetic navigation system (MNS) and the magnetic force accounts for the ME robot to align and propel in the direction of the Human Epithelial cell (HEP). The ME robot on reaching the HEP can generate electric pulses due to its magnetoelectric property and hence create nano-sized pores on the cell membrane. The focus of this paper is to understand the real time changes occurring in the conductivity and induced transmembrane potential of the cell when the CFO-BTO is brought in the vicinity of the HEP cell. The low magnitude of a single CFO-BTO that produced 0.625V of electric field can cause an induced transmembrane potential of approximately 7µV but the synchronized ME robot can produce a higher potential change that can allow for the pore creation. An estimation in the change in the conductivity of the cell is performed using an analytical -equivalent conductivity of a permeabilized cell approach and shown an increased conductivity due to the creation of nanopores and its correlation with the induced transmembrane potential. This real time theoretical analysis allows scope for future designing and understanding the application of the CFO-BTO robot in the drug delivery procedure in a cell.

Magnetoelectric layered composites can be designed to exhibit the magnetoelectric effect based on transfer of stress from magnetostriction of ferromagnetic layer to the ferroelectric layer. In this study Core-Shell magnetoelectric nanoparticles (CSMEN) have been fabricated by coating BaTiO3 on CoFe2O4 nanoparticles (∼50nm) by molar mass ratio using hydro-thermal method. The control factor in the fabrication process is the use of different shape and morphology of the CoFe2O4 core. The crystallinity of the barium titanate (BT) coating changes from single crystalline to polycrystalline nature depending on the BT coating thickness. The BT shell thickness during CSMEN fabrication largely varies with the morphology of the substrate which is the cobalt ferrite nanoparticle. The shape, size and coagulation are the morphological characteristics of cobalt ferrite nanoparticles which plays major role for single crystalline BT coating on it. The bigger the size or the uneven surface morphology/shape of cobalt...

In this paper, three well-known prototypic ferroic materials, BaTiO3, PbZr0.4Ti0.6O3 and Fe3O4, were experimentally and theoretically investigated to explore the origin of their respective ferroic state. Their structural properties were determined by X-ray powder diffraction and Rietveld refinement. The electron density distribution around cationic and anionic sites were obtained by using the Maximum Entropy Method on analyzing the X-ray diffraction results. Electron density distributions and the electronic band structures were determined by Density Functional Theory simulations using experimental and refined structural parameters as input data. The results show a strong correspondence for all the obtained properties and features, suggesting the important role of structural aspects and chemical bonding in the stabilization of the ferroic states in each studied system.

This work presents experimental investigation of the low-temperature dielectric and ultrasonic responses of (Ba1−xSrx)TiO3 ceramics with high strontium concentration compositions, x > 0.825. Impedance spectroscopy measurements were performed at frequencies between 0.1 kHz and 100 kHz, and the results were correlated to those obtained with ultrasonic measurements. The anomalies observed in ultrasonic data were associated to ferroelastic and ferroelectric phase transitions. For x = 0.875 the “pinching” of ferroelectric phase transitions was observed. A brief discussion associates some peaks in the ultrasonic attenuation to anomalies in the dielectric response at temperatures below phase transition.

This paper reports the electric, magnetic and magnetoelectric properties of particulate composites of the system with ferroelectric phase 0.675[Pb(Mg1/3Nb2/3)O3]−0.325[PbTiO3] and magnetic phase CoFe2O4 prepared by Spark Plasma Sintering technique. Optimized sintering and thermal annealing parameters were applied in order to achieve highly dense microstructure with sub micrometric grain size distribution for both phases. The results from the dielectric measurements showed a diffuse and dispersive phase transition. P-E and M-H loops revealed the simultaneous existence of ferroelectric and ferrimagnetic ordering, respectively. Moreover, at cryogenic temperatures an anomalous behavior on the bias magnetic field dependence was observed for the magnetoelectric voltage coefficient.

The study of multiferroic crystalline materials is of great technological and academic interest due to the correlation between their ferroelectric and ferromagnetic properties. In this work, ferroic properties of Nd-modified (A-site substitution) BiFeO3 (BNFO) compounds were studied. Ceramic compositions of Bi1-xNdxFeO3 (x = 0.10 and 0.20) were obtained through a route that included high-energy ball milling, isostatic pressing (to obtain the ceramic shape) and sintering in air. The X-ray diffraction data showed that these compositions have a distorted perovskite structure, with relative densities reaching 93%. Dielectric measurements showed a frequency independent step-like relaxation for the Bi0.9Nd0.1FeO3 composition and indicatives indications of thermally activated conduction processes for the Bi0.8Nd0.2FeO3 composition. Magnetic studies showed a breakdown of the typical magnetic cycloidal structure of BiFeO3.

Layered composite electro-ceramics can be designed to exhibit the magnetoelectric (ME) effect based on stress transfer from magnetostriction of ferromagnetic layer to the ferroelectric layer. Many studies in search of giant ME coefficients in layered composites have been made but there are less studies regarding the ME effect in these ceramic materials as a function of temperature, mainly at low temperatures. With the influential increase in magnetoelectric sensing devices use in extreme, minute or precise field monitoring, a broadband temperature dependent analysis on ME effect of these sensors is much required. In this work the effect of temperature on ME effect in a NiFe2O4/Pb(Zr0.52Ti0.48)O3/NiFe2O4 layered composite are studied and any major/minute change have been analyzed. Dynamic ME measurements shows a maximum linear ME coefficient (αME = 238 mV/cm.Oe) by applying an AC magnetic field in a frequency of 600 Hz at room. Highly reduced αME values are observed at low temperatures. Magnetocapa...

Optical and microstructural characteristics of sol–gel-deposited multilayer Pb(Zr0.52Ti0.48)O3 thin films were investigated employing several analytical techniques both invasive and non-destructive types. Optical responses probed by variable angle spectroscopic ellipsometry (VASE) were used to derive the optical properties and geometrical parameters of the multilayer thin films. STEM and TEM studies were performed to verify the nano-structural specifics and to correlate the results obtained using VASE. Crystallographic orientation and epitaxial interrelations of the layers were also investigated using selected area diffraction patterns with compositional profiles derived from energy dispersive X-ray analysis. Ferroelectric domain switching of the sol–gel-deposited films were studied by Piezoelectric Force Microscopy (PFM) revealing both the polarization–electric field hysteresis (P-E loop) relation and the butterfly-shaped surface displacement amplitude responses. The advantages and limitations of the non-invasive VASE characterization technique in terms of resolving a multilayer structure of thin films were explored in detail.

The magnetoelectric (ME) effect has been investigated in lead zirconate titanate (PZT) thin film deposited on nickel foil using chemical solution deposition (CSD) technique. The synthesized PZT thin films are found to possess perovskite structure without presence of any intermediate layer. PZT thin film deposited on nickel foil exhibits a good ferroelectric property with a high remnant polarization of about 86 µC/cm2.The ferroelectric loop has been modeled using domain wall theory to verify the behavior of the ferroelectric domains. It is observed that deposition conditions, specially annealing temperature, play a crucial role in enhancing the magnetoelectric effect. A high ME coefficient of 220 mVcm–1Oe–1 at a bias magnetic field of 50 Oe has been obtained due to enhanced magnetoelectric coupling between PZT film and nickel foil.

The phase transition, ferroelectricity, piezoelectricity, and ferromagnetic characteristics of Bi 1− x (Ba 0.75 Ca 0.25 ) x Fe 1− x Ti x O 3 ( x = 0.2–0.4) ceramics have been systematic studied. The rhombohedral R3c and tetragonal P4mm phases are determined for x = 0.2 and x = 0.4, respectively, and the composition of x = 0.3 indicates the rhombohedral and tetragonal diphase structure. The saturated P – E loop with a significantly enhanced remnant polarization ( P r ∼43 μC/cm 2 by dynamic hysteresis mode (DHM); P r ∼24 μC/cm 2 by positive up negative down (PUND) method) is determined in Bi 0.7 (Ba 0.75 Ca 0.25 ) 0.3 Fe 0.7 Ti 0.3 O 3 ceramics at room temperature. The coercive field is greatly suppressed with increasing x . The enhanced remnant magnetization (0.07 emu/g at 300 K) is also achieved in the optimal composition x = 0.3. The room temperature strain–electric field (s–E) curves indicates a large strain ∼0.2% in the composition of x = 0.3. The comprehensive enhancement of ferroelectricity, piezoelectricity, and magnetization in composition of x = 0.3 suggests that introducing phase boundary is a promoting way to put BiFeO 3 ceramics towards applications.

Made available in DSpace on 2018-12-11T16:59:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-10-13 In this work, the structural, ferroelectric and dielectric properties, including radio-frequencies and microwave region, has been investigated in Pb1-xLax(ZryTi1-y)1 - (x/4)O3 (PLZT) ferroelectric ceramics, where x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.12 and y = 0.70. Ceramic samples were obtained from the solid-state reaction sintering method, and the dielectric measurements were performed in a wide frequency and temperature region, below and above the paraelectric-ferroelectric (PE-FE) phase transition temperature. The structural properties, investigated at room temperature, from the x-ray diffraction (XRD) technique, revealed the evolution from the rhombohedral (R3m symmetry) to orthorhombic (Pmmm symmetry) phases, with the increase of the lanthanum concentration. The ferroelectric as well as the low frequency dielectric properties revealed a change in the PE-FE phase transition characteristics from a normal to a relaxor behavior, with the increase of the lanthanum content. On the other hand, the high-frequency (microwave) dielectric properties studied at room temperature, showed a strong dielectric dispersion on both normal (x≤0.06) and relaxor (x>0.06) compositions, which indeed revealed to be also strongly dependent on the lanthanum concentration. Department of Electrical and Computer Engineering College of Engineering University of Texas at San Antonio Grupo de Ferroelétricos e Materiais Multifuncionais Instituto de Física Universidade Federal de Uberlândia Departamento de Física e Química UNESP Campus de Ilha Solteira Departamento de Física e Química UNESP Campus de Ilha Solteira

The study of multiferroic materials is of great technological and academic interest because the correlation between ferroelectric and ferromagnetic properties. Among these materials, the compounds with perovskite structures such as those based on BiFeO3 are extensively studied. In this study BiFe1-yCoyO3 ceramics were processed by high-energy ball-milling followed by isostatic pressing to shape the ceramics and, finally, fast sintering in an air atmosphere. X-ray diffraction data pointed out to compositions with rhombohedral symmetry and space group R3c. Dielectric and magnetic measurements were performed to study the ferroic properties of obtained compositions. Thermally activated conduction processes were observed from dielectric permittivity and loss tangent measurements; magnetic studies showed a breakdown of the magnetic cycloidal structure typical of BiFeO3.

The presence of piezoelectricity, pyroelectricity and ferroelectricity in biological samples has been envisaged since the 1950s, the earliest studies being done on wood, bones, collagen, etc. Pioneer work reporting piezoelectricity in bones, tendons, dentin, etc. has been in existence for quite some time however it was only in the recent past that ferroelectricity was suggested to be present in bio-species like aortic wall, nail and certain form of shells. Recent focus of uncovering bio-ferroelectricity has progressed into natural and artificial bio-molecules such as glycine, peptides, tubulin, etc due to the advancement in instrumentation with nanoscale measurement capabilities. This paper makes an attempt to discuss the chronological developments in the field of ferroelectricity in biological samples, recent upsurge in this field of science with the aid of better resources and our perspective of bio-ferroelectricity/bio-multiferroicity along with experimental results on some selected biological material...

Multiferroic behavior of magnetoelectric nanoparticles exhibiting both ferromagnetic and ferroelectric properties find significance in various applications. In this study, core-shell magnetoelectric nanoparticles (CSMEN) have been fabricated by coating CoFe2O4 nanoparticles with BaTiO3 by weight using hydro-thermal method. The core-shell structure was confirmed by electron microscopy and topographic scanning probe microscopic measurements were performed for further structural analysis. While magnetic force microscopy and ferromagnetic hysteresis loop measurements substantiated ferromagnetic behavior of the core, piezo response force microscopy confirmed ferroelectric behavior and single crystalline nature of BaTiO3 shell. As analyzed by TEM diffraction pattern both core and shell are in cubic phase with their respective diffraction spots depicting their single crystalline nature.

Perovskite (Pb(1–3x/2)Bix)(Zr(1–3x/4)Ybx)O3 (PZ-BY) ceramics, where x = 0.01–0.10, were synthesized by conventional solid state reaction. The effect of BiYbO3 on crystal structure, phase transitions and electrical properties was studied as a function of composition. The X-ray diffraction (XRD) result indicated that the perovskite structure with orthorhombic symmetry was a major phase for all samples. The pyrochlore phase, identified as Yb0.2Zr0.8O1.9, coexists in PZ-BY ceramics. The influence of instability and a small tolerance factor (t) and the average electronegativity difference () of pure BY on phase formation of PZ-BY ceramic has been discussed. Furthermore, it was found that adding small tolerance factor BiYbO3 compound can stabilize the antiferroelectric (AFE) phase of PZ solid solutions and decreasing t of solid solution can enhance Curie temperature of PZ.

Ferroelectric-relaxor behavior on highly epitaxial Barium Zirconium Titanate (Ba (Zr0.2Ti0.8)O3) thin film was investigated using the Piezoresponse Force Microscopy specifically to investigate the onset of relaxor behavior. The surface roughness, microstructure and the grain size of the film were systematically studied. Ferroelectric switching at random localized points were observed at room temperature though it has been previously reported that the phase transition in BZT-20 occurs at 285K. Phase reversal with the reversal of the applied voltage was also seen. Scanning Capacitance Microscope has been employed to interrogate the localized change in the capacitance with change in voltage. The thin film sample showed the presence of ferroelectric nanoregions at room temperature unlike its bulk counterparts which is paraelectric at room temperature.

The dielectric properties of PbZr 0.65 Ti 0.35 O 3 –BaFe 12 O 19 (PZT–BaM) multiferroic ceramic composites, obtained from the conventional solid-state reaction method, have been investigated. While there is some dielectric dispersion at low frequencies, the highly-stable values of dielectric permittivity over a wide frequency range, together with low dielectric losses (~10 −3 ), make these composites suitable for practical radio-frequency and potential microwave device applications. Toward high frequencies, the data reveal an anomalous resonance-like phenomenon. This resonance phenomenon is connected to an over-damped resonance mechanism for the vibration of the boundaries of polar regions, associated with the ferroelectric phase. A noticeable dependence of the parameters characterizing this last dielectric dispersion with the BaM concentration is found, indicating a strong influence of the magnetic phase on the dynamics of the ferroelectric domain-wall motion.

Highly oriented multilayerd Ba(Zr0.1Ti0.9)O3/(Ba0.75Ca0.25)TiO3 thin films were fabricated on Nb doped (001) SrTiO3 (Nb:STO) substrates by pulsed laser deposition. Microstructural characterization by X-ray diffraction indicates that the as-deposited multilayered thin films are highly c-axis oriented. Transmission electron microscopy shows that the films present epitaxial correspondence with the substrate at the first layer and multi-oriented twin domain structures near the surface, especially with increasing periodic number (N). Piezoresponse force microscopy (PFM) studies reveal an intense polarization component in the out-of-plane direction, which increases greatly with increasing periodic number (N), whereas the in-plane shows inferior phase contrast. The optimized combination was found to be the annealed 16 layer structure (N = 8, layer thickness = 712 nm) which displays the best polarization domain structures and the saturated piezo response loop. The annealing process benefits the 180° domains with the same angle in the growth direction, which brings more piezo response in the in-plane signal. Our results suggest that the increasing of piezo response is greatly associated with the interface effect and the twining structure.

In the last decade, a tremendous amount of research works have been carried out in the area of multiferroic nanostructure materials in order to meet the requirement of science and technology for the future microelectronic industries. The potential functionalities of any kind nanostructure materials lies in the vicinity of large surface to volume ratio compare to the bulk counterpart. The new technology for microelectronics require small dimension, robust mechanical properties, higher degree of electrical and electronic properties and finally high output power with low dissipation energy. The area of ferroelectric and multiferroic nanostructures are vast, this chapter deals with the different variety of multiferroic nanostructure with different dimensionality (D) 0D 1D, 2D and 3D and their state of art characterization process. Possible and feasible theoretical modeling and related experimental facts of already established multiferroics nanostructures will be described. It will also cover the advantages an...

The dielectric relaxation processes have been investigated in multiferroic ceramic composites based on the ferroelectric PbZr 0.65 Ti 0.35 O 3 (PZT) and ferrimagnetic BaFe 12 O 19 (BaM) systems. The frequency dispersion of the complex dielectric permittivity was analyzed over wide frequency and temperature ranges, and the effect of BaM content is depicted. The activation energies for the relaxation processes were also obtained for all the studied compositions and the results suggest the oxygen vacancies-related hopping mechanism to be responsible for the observed behaviors in the studied composites. Furthermore, an anomalous behavior in the activation energy has been observed with the increase of the BaM concentration. The obtained results are discussed within the framework of current models reported in the literature for dielectric relaxation processes.

The paper encompasses the investigation of the effective pyroelectric behavior of materials in different structures/systems such as the bimorphs and the sandwiched structure, with the variation of the temperature. Different mathematical approaches have been used to include the secondary factors contributing to the effective pyroelectric coefficient, and it has been included to obtain a consolidated expression of the same. The effective pyroelectric coefficient for few selected ferroelectric materials has been deduced using their actual physical constants to get a closer resemblance with the practical device. This paper would be a step forward to the fabrication of layered material with a higher pyroelectric coefficient for a possible energy harvesting applications also.

Magnetoelastoelectric coupling in an engineered biphasic multiferroic nanocomposite enables a novel magnetic field direction-defined propagation control of terahertz (THz) waves. These core–shell nanoparticles are comprised of a ferromagnetic cobalt ferrite core and a ferroelectric barium titanate shell. An assembly of these nanoparticles, when operated in external magnetic fields, exhibits a controllable amplitude modulation when the magnetic field is applied antiparallel to the THz wave propagation direction; yet the same assembly displays an additional phase modulation when the magnetic field is applied along the propagation direction. While field-induced magnetostriction of the core leads to amplitude modulation, phase modulation is a result of stress-mediated piezoelectricity of the outer ferroelectric shell.

The conductive processes in multiferroic ceramic composites based on PbZr0.65Ti0.35O3 (PZT) and BaFe12O19 (BaM), synthesized by the conventional solid-state reaction method, have been investigated. The DC and AC electrical conductivities have been analyzed in a wide temperature and frequency range and the influence of the BaM content on the electrical properties of the PZT–xBaM composites has been taken into account. It has been observed that the inclusion of the BaM in the PZT ferroelectric matrix promotes conduction mechanisms with magnetic-order characteristics on the ceramics, which were related to doubly ionized oxygen vacancies, superexchange, and double-exchange-type interactions. The obtained results are discussed in the framework of Jonscher's formalism.

The lead-free AlFeO3-based compounds are attractive multiferroic materials, as those present piezoelectricity and ferrimagnetism at low temperatures. In this work the synthesis and ferroic properties of AlFeO3-based ceramics were investigated. Stoichiometric proportions of the precursors - α-Fe2O3 and α-Al2O3 - were milled and sintered to obtain AlFeO3 ceramics. Also, AlFeO3 ceramics doped with 2at% of Nb2O5 or MnO2 were sintered in oxygen flow at 1700 K. The crystal structure of the samples was studied by X-ray diffraction. The diffractograms were refined by the Rietveld method. The results obtained from refinements showed an orthorhombic symmetry with space group Pna21. Dielectric, ferroelectric and magnetic investigations suggested a magnetoelectric coupling between the electric and magnetic orderings at temperatures below ∼ 160 K for AlFeO3, Al(Fe0.98Nb0.02)O3 and Al(Fe0.98Mn0.02)O3, where the compositions show the ferromagnetic and ferroelectric ordering.

The ferroic properties (ferroelectric and magnetic) of a PZT/Ba-ferrite (PZT–BaM) based ceramic composite, obtained from the conventional solid state reaction method, have been investigated. Results, obtained at room temperature, revealed intensified characteristics of both ferroelectric and magnetic responses, which make these composites a topic of studies and exploring applications in magneto-electric related devices.

(Bi0.5Na0.5)Zr1-xTixO3 with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 ceramics were fabricated by a conventional sintering technique at 850–950°C for 2 h. From X-ray diffraction study, three regions of different phases were observed in the ceramic system i.e., orthorhombic phase region (0 ≤ x ≤ 0.2), mixed-phase region (0.3 ≤ x ≤ 0.4), and rhombohedral phase region (0.5 ≤ x ≤ 0.6). The observed diffuse dielectric phase transition could be correlated to the compositional inhomogeneity of the samples. The dielectric properties as a function of the temperature at different frequency indicated normal ferroelectric behavior in BNZ and BNZT ceramics. The phase transformation from orthorhombic phase to rhombohderal phase affected significantly the dielectric enhancement and decrease of the maximum temperature in this ceramic system.

Environment-friendly Ferroelectric Mn:BST//Mn:BZT multilayer with additional 2% Mn doping were epitaxially fabricated on (001) MgO substrates by pulsed laser deposition with same thickness but different stacking periodic numbers or each layer thickness. Microstructure studies by X-ray diffraction and transmission electron microscopy indicate that the multilayer is c-axis oriented with good epitaxial nature. The microwave (∼18GHz) dielectric property measurements show that the dielectric loss tangent rapidly decreases with the increase of each layer thickness. The loss tangent can be lowered down to ∼0.043 at ∼18GHz, which suggests that the Mn:BST//Mn:BZT multilayer system has great potential for the development of room temperature microwave elements and related applications.

Graphical abstract: - Highlights: • Lead-free K{sub 0.95}Li{sub 0.05}Ta{sub 1−x}Nb{sub x}O{sub 3} single crystals were grown using the top-seeded melt growth method. • The piezoelectric and ferroelectric properties of as-grown crystals were systematically investigated. • The piezoelectric properties are very attractive, e.g. for x = 0.60 composition, k{sub t} ≈ 70%, k{sub 31} ≈ 70%, k{sub 33} ≈ 77%, d{sub 31} ≈ 230 pC/N, d{sub 33} ≈ 600 pC/N. • The coercive fields of P–E hysteresis loops are quite small, about or less than 1 kV/mm. - Abstract: Lead-free potassium lithium tantalate niobate single crystals with the composition of K{sub 0.95}Li{sub 0.05}Ta{sub 1−x}Nb{sub x}O{sub 3} (abbreviated as KLTN, x = 0.51, 0.60, 0.69, 0.78) were grown using the top-seeded melt growth method. Their piezoelectric and ferroelectric properties in as-grown crystals have been systematically investigated. The phase transitions and Curie temperatures were determined from dielectric and pyroelectric measurements. Piezoelectric coefficients and electromechanical coupling factors in thickness mode, length-extensional mode and longitudinal mode were obtained. The piezoelectric properties are very attractive, e.g. for x = 0.60 composition, k{sub t} ≈ 70%, k{sub 31} ≈ 70%, k{sub 33} ≈ 77%, d{sub 31} ≈ 230 pC/N, d{sub 33} ≈ 600 pC/N are comparable tomore » the lead-based PZT composition. The polarization versus electric field hysteresis loops show saturated shapes. In short, lead-free niobium-rich KLTN system possesses comparable properties to those in important lead-based piezoelectric material nowadays.« less

Lead-free ferroelectric niobium-rich potassium lithium tantalate niobate K 0.95 Li 0.05 Ta 1− x Nb x O 3 (KLTN) single crystals were grown by the top-seeded melt method. Thermal expansion properties of K 0.95 Li 0.05 Ta 1− x Nb x O 3 ( x =0.78, 0.69, 0.60, and 0.52) single crystals were investigated in the temperature range of 140 K–800 K using a dilatometer. According to the thermal expansion data, phase transition temperatures of all compositions were determined, and temperature dependence of local polarization was calculated. In addition, the results were discussed in combination with the composition and crystallographic orientation.

Multiferroics are an important family of materials with special properties suitable for applications in advanced technological devices. In most of the cases, the ferroelectric ordering and domain wall formation determine and control their operation and functionality. However, the physical mechanisms by which these domain walls are formed are still not yet completely clarified. Also, in the last few years, few advances are found in the mechanisms used to explain the domain walls and their influence on the materials properties. In this work, the domain walls in ferroelectric multiferroics were investigated by using high-resolution transmission electron microscopy and image simulations. The ferroelectric switching was also observed by piezoresponse force microscopy. A three-dimensional atomic-level framework of 90° ferroelectric domain walls was proposed and the structural and ferroelectric features at the domain walls, such as length, width, and angle between domains, were determined. From these studies, it was found that ferroelectric and structural features of multiferroic BiFeO3–PbTiO3 compounds, such as domain-orientation, electrical conductivity, magnetic ordering, and brittleness due to strains at the domain walls, can be controlled by particular atomic substitutions at the A site of the perovskite structure.

Ultrashort THz pulses overlap with resonances through which magnetism or ferroelectricity can be probed or controlled. Low energy modes like soft mode phonons associated with the atomic displacements that result in ferroelectricity, or spin waves in magnetically ordered systems which can be either magnetic dipole active, in the case of the magnons, or electric dipole active in the case of electromagnons can be controlled using THz pulses. The interesting thing about multiferroics is that these modes can potentially be used for ultrafast magnetoelectric control. In common ferroics and multiferroics these modes often overlap well with the spectra of typical ultrashort THz pulses. In this work we exploit that unique feature of Terahertz ultrashort pulses to report on the multiferroic domain characterization of Bismuth Ferrite and Lead Iron Niobate correlating its ferroic behaviors, enhanced or reduced,with its varying doping concentration in the terahertz regime.The material properties like index of refraction and absorption coefficient thus derived using optical interferometry can be further explored for ultrafast device configuration.