Ferroelectric Nature Research Articles

Strain induced electromagnetic coupling in tri-phase multiferroic composites 0.8[(1-x)Fe2O3–xPbZrO3]+0.2Cr2O3 for multistate devices

Multiferroic composites are highly desirable for next-generation multifunctional smart devices because of their low power consumption, fast data processing, and nonvolatile nature in memory devices. Here we synthesized a series of tri-phase composite of Fe2O3, PbZrO3, and Cr2O3 with general formula 0.8[(1-x)Fe2O3–xPbZrO3]+0.2Cr2O3 (x = 0.0, 0.33, 0.66 and 1.0) via a chemical approach. Individual oxides are synthesized by the sol-gel auto-combustion method and the solid-state route is used to mix them. Through structural analysis, the formation of tri-phase composites is confirmed by the presence of peaks belonging to each phase. The morphological study suggested that the composites have a homogeneous distribution of grain size over the surface with small voids. To investigate the ferroelectric nature of these composites the saturation polarization, remanent polarization, and coercivity are calculated from their P-E loops. Using these values, the switching charge density and recoverable energy density are evaluated which highlighted the importance of these composites for fast switching and energy storage devices. The response of variation in polarization by the magnetic field is mapped by magneto-electric coupling measurement. Our results show that these tri-phase composites with ferroelectric and magnetoelectric response are potential candidates for high-density data storage and ME multifunctional devices.

Synthesis and Transport Properties of Cobalt Ferrite: A Systematic Overview

: CoFe2O4, the single-phase nano crystalline materials, has potential applications in information storage, sensors and actuators. This ferrite has a tetragonal P4mm crystallographic structure and having crystallite size 42 nm. The CoFe2O4 is prepared by different techniques. The spinal structure of dielectric and hysteresis study disclosed ferroelectric nature over a broad spectrum of frequency and temperature with low dielectric loss. Based on Spinal structure phase metal oxides, a distinct range of properties became useful for different applications. Spinal structure materials have attractive characteristics in electrical conductivity, dielectric constant, dielectric loss, structural, and magnetic properties. Spinal structure materials showed efficient essential properties for photovoltaic solar cells.

Spin reorientation behavior and enhanced multiferroic properties of co-doped YFeO3 towards a monophasic multiferroic ceramic Co0.05Y0.95Fe0.95Ti0.05O3

Monophasic nanocrystalline lead-free relaxor ferroelectric samples of YFeO3 and Co0.05Y0.95Fe0.95Ti0.05O3 were prepared via the standard sol-gel synthesis method. The influence of Co and Ti co-doping on the structural, dielectric, ferroelectric, and magnetic properties were investigated using X-ray, Neutron Diffraction, Electric Polarisation, and magnetization measurement techniques. The structural analysis by the Rietveld method revealed an orthorhombic (Pnma) distorted perovskite structure. The analysis of the neutron diffraction data showed a spin reorientation from IR Γ4 to Γ2 in the doped sample. The universal dielectric response (UDR) phenomenon was used to explain the dielectric behavior. The temperature-dependent dielectric constant measurement shows a shift in the ferroelectric to paraelectric phase in Co0.05Y0.95Fe0.95Ti0.05O3. The observed P-E loops indicate lossy ferroelectric nature for YFO and CYFTO. Enhancement in the value of saturation magnetization at room temperature was observed on co-doping. Furthermore, the presence of magnetodielectric coupling was established for the co-doped sample. Co-doping with Co and Ti in YFeO3 enhanced the multiferroic properties of the pristine sample which may be helpful for future device applicability.

Enhanced ferroelectric properties in B-site Sn doped Pb0.9Mn0.1Zr0.52Ti0.48O3

Polycrystalline compounds of Sn substituted Pb0.9Mn0.1(Zr0.52Ti0.48)1-xSnx O3 (where x = 0.05,0.1) are synthesized by conventional ceramic method. Raman spectroscopy study reveals the tetragonal structure of Sn substituted samples. Impedance spectroscopic studies reveal the non-Debye kind of relaxation process in the material. Grain and grain contribution to the electrical conduction was observed. The observed P-E hysteresis confirmed the ferroelectric nature of all the samples. With the increase of Sn doping, Pr, Ps and Ec values also increased.

Fabrication of Ferroelectric Gate Thin‐Film Transistors with a Lanthanum‐Doped HZO Gate Insulator and Indium‐Tin‐Oxide Channel via a Solution Process

In recent years, lanthanum‐doped hafnium–zirconium dioxide (La‐HZO) has garnered attention as a material for application in ferroelectric devices; moreover, atomic layer deposition has been applied to prepare La‐HZO films with metal–ferroelectric–metal structures. This article describes the fabrication of ferroelectric La‐HZO thin films on Pt/Ti/SiO2/Si substrates via a solution process. The dependence of the electrical properties on the La concentration of La‐HZO films annealed at 800 °C in vacuum is also discussed. The film with a La concentration of 8 at% exhibits the highest remanent polarization, whereas undoped HZO exhibits paraelectric behavior. Additionally, the leakage current of La‐HZO specimens tends to be significantly lower than that of undoped HZO. Furthermore, a higher annealing temperature corresponds to better ferroelectric properties and a lower leakage current. The characterization of fabricated ferroelectric gate thin‐film transistors (FGTs) with an 8 at% La‐HZO gate insulator and indium‐tin‐oxide channel is shown to confirm typical n‐channel transistor operation, i.e., a counterclockwise hysteresis loop in the transfer curve; this is attributable to the ferroelectric nature of the La‐HZO gate insulator. The results demonstrate that the proposed FGT design offers a low subthreshold voltage swing, high on/off drain current ratio of 106, large on‐current, and large memory window.

Electrical property and phase transition analysis of KNN-based lead-free ferroelectric films

The electrical properties, phase construction, thermal stability and phase transition behavior are investigated in 0.95(K0.49Na0.49Li0.02)(Ta0.2Nb0.8)O3–0.05BaZrO3 with 2 wt% MnO2 (KNNLT-BZM) lead-free epitaxial ferroelectric film on LaNiO3 (LNO)-coated SrTiO3 (STO) (001) substrate. The x-ray diffraction results show that a mixed orthorhombic (O) and tetragonal (T) phase is obtained in KNNLT-BZM film. The MnO2 doping can effectively suppress its leakage current, which greatly improves the electrical performance featured by a lower leakage value of 8 × 10–11 A cm−2, a twice remnant polarization of 44.7 μC cm−2, and frequency-dependent ferroelectricity between 50 Hz and 10 kHz. Strikingly, the KNNLT-BZM film maintained ferroelectric nature up to 200 °C, and exhibit a phase transition from O + T mixed phase to T phase (T Mix-T) at 300 °C with a high Curie temperature above 440 °C. These results suggest great application potentials of KNN-based films in lead-free micro-electronic devices.

Electrostatic Coupling in MoS2/CuInP2S6 Ferroelectric vdW Heterostructures

AbstractFerroelectric van der Waals (vdW) heterostructure have recently emerged as a low‐power, versatile device paradigm because it combines the great diversity of the 2D materials and the memory nature of ferroelectrics. The non‐volatile field effect generated by the polarization bound charge is the pivotal factor for the device's performance. Unfortunately, microscopic studies on the interplay between polarization switching and electrostatic coupling at the heterojunction remain largely overlooked. Herein, the authors investigate the electrostatic coupling phenomena of vdW heterostructures consisting of semiconducting MoS2 and ferroelectric CuInP2S6. Significant charge injection accompanying the polarization reversal appears to be the governing field effect that modulates the electronic and photoluminescent properties of MoS2, as revealed by correlated ferroelectric domain, surface potential, and photoluminescence microscopies. Conversely, the photoactivity of the MoS2 also affects the polarization stability of CuInP2S6. This work provides direct microscopic insight into the mutual electrostatic interactions in vdW ferroelectric‐semiconductor heterojunctions, which has broad implications for ferroelectric field‐effect applications.

Exploring magneto-electric nanoparticles (MENPs): a platform for implanted deep brain stimulation

Exploring magneto-electric nanoparticles (MENPs): a platform for implanted deep brain stimulation

Thermally Stable Piezoelectric Performance of MnO2 Inserted Pseudo-tetragonal Phase Existent CaBi2Nb2O9-based Ceramics

ABSTRACT Pseudo-tetragonal phase boundary existent Ca0.60(Li0.5Bi0.5)0.40Bi2Nb2O9:xwt%MnO2 (CBNL:xMn) ceramic series is fabricated to investigate the ferroelectric and piezoelectric properties. Pure CBNL and CBNL:xMn ceramics have maintained their pseudo-tetragonal phase boundary even after the insertion of Mn ions. The addition of MnO2 in CBNL has improved the multifunctional properties of material at x = 0.20. CBNL:0.20Mn has shown the relative density of 98%, saturated polarisation (PS ) of ~ 13.5 µC/cm2, high piezoelectric coefficient (d33 ) of ~ 25 pC/N, and high impedance of ~ 8.9 × 108 Ω at room temperature, which are the much improved values as compared to pure CBN or CBNL ceramics. The dielectric constant (ɛr ) dependence on temperature is presenting the sharp peak of CBNL:0.20Mn ceramic at Curie temperature (TC ) ~ 918°C confirming the strong ferroelectric nature of the ceramic. Importantly, poled CBNL:0.20Mn ceramic has shown the thermally stable depoling performance, which remains 92% (23 pC/N) of its initial room temperature value even after annealing the sample at 800°C. Results indicate the clear significance that the introduction of multivalence Mn ions in the pseudo-tetragonal existent region of CBNL has improved the multifunctional properties of the material, making it a strong candidate to be utilised in actuators and high-temperature piezoelectric devices.

Impact of A-site calcium on structural and electrical properties of samarium cobaltite perovskites

Perovskite structured samarium cobaltite ceramics materials having good electric, dielectric and modulus characteristics are used as potential candidate in several device applications. The present study discusses the structural and dielectric properties of Sm1-xCaxCoO3 (x = 0.0,0.05,0.1,0.2,0.3) (SCC) synthesised by high temperature solid state reaction method. The x-ray diffraction analysis confirmed the orthorhombic phase for the synthesised samples at room temperature. Scanning electron microscopy of the sample strongly supports the formation of regular distribution of grains with desirable density. The impedance, dielectric permittivity and modulus spectrum of SCC were studied in a wide frequency (100 Hz-1MHz) range at various temperature. From the complex modulus analysis, the conductivity relaxation in SCC have been studied. The dependence of dielectric properties of these material on frequency indicates its ferroelectric nature. AC conductivity formalism has also been studied.

Electrical transport properties of La doped BiFeO3-NaNbO3 composite

ABSTRACT The composites, (1−x)(BiFe1-yLayO3)– xNaNbO3 with x = 0.25, 0.45 and y = 0.10, 0.20, are prepared by mixed oxide method. XRD analysis shows rhombohedral (hexagonal) structure at room temperature. The properties such as dielectric loss (tanδ) and dielectric constant (ϵr ) of all the samples are studied. A significant improvement in dielectric constants has been observed with the rise of Lanthanum (La) content. A dielectric anomaly above 350°C is observed for all the studied materials. Further, it is observed that ac conductivity (σ ac) spectrum obeys universal Jonscher’s power law. The variation of σ ac with inverse of temperature for all the samples is found to obey the Arrhenius equation. The formation of loop in polarisation verses electric field curve establishes the ferroelectric (FE) nature of all the studied samples. Current (I)-Electric Field (E) loops is studied to show the behaviour of domain switching.

Relaxor ferroelectricity and low microwave dielectric permittivity of Sr(1-x)CexTi(1-2/3y)MgyO3 ceramics

The structural instability, relaxor ferroelectricity and microwave dielectric (MWD) properties of Sr(1-x)CexTi(1-2/3y)MgyO3 (sintered in 5%H2 and 95%N2 atmosphere) samples were systematically studied. The ceramic sample with x = 0.05 shows cubic symmetry by x-ray diffraction (XRD). However, for x ≥ 0.1 the existence of superlattice and peaks splitting, clarify the existence of tetragonal symmetry. For x = 0.1, the SEM-EDX maps indicates the formation of a complete solid solution with a dense microstructure. For all samples, the presence of a frequency-dependent dielectric maxima (ε′−T plot) and intrinsic ferroelectricity (PUND) clarifies the relaxor ferroelectric nature. More interestingly, the sample with x = 0.15 shows a low microwave dielectric permittivity (εr) of 19, temperature coefficient of resonance frequency (TCF, τf) of +87 ppm/°C, and the Q × f value of 302 GHz, respectively.

Analytical study of the ferroelectric properties of Fe-doped KNbO3 single crystal

We report herein the structural, dielectric, ferroelectric, and domain properties of an Fe-doped potassium niobate ([KNbO3] KNb1-xFexO3; x = 0.01 mol%) single crystal synthesized by a flux method. X-ray diffraction (XRD) results illustrate that the given sample adopts orthorhombic crystal symmetry with the space group Amm2. On submitting the sample to differential thermal analysis (DTA), two endothermic peaks were observed, the first at 224 °C and the second at 425 °C. Dielectric studies with respect to temperature from 30 to 500 °C showed that the Curie temperature (Tc) of the Fe-doped KNbO3 single crystal occurred at 435 °C. The measured dielectric loss of the crystal is in good agreement with other dielectric studies. The relationship between polarization and electric field (PE) shows that the spontaneous polarization (Ps) and coercive field (Vc) for the doped material are lower than those for an undoped KNbO3 single crystal, indicating a weakly ferroelectric nature of the sample. A trinocular microscope has been used to study the domain properties and revealed the formation of 60° and 90° domain walls. Furthermore, upon etching the single crystal with nitric acid (HNO3), etch pits and a twinning plane of the domains were formed. Finally, electric fields of 100, 500, and 1000 V/cm were applied to the Fe-doped KNbO3 single crystal surface, whereupon the nucleation and dissipation of new domains could be observed.

Thickness‐Driven Morphotropic Phase Transition in Metastable Ferroelectric CaTiO3 Films

AbstractThe intimate coexistence of multiple phases in ferroelectrics has been shown to result in exotic electromechanical properties, such as giant piezoelectricity. Here, via a thickness‐driven phase transition, the phase coexistence and enhanced piezoelectricity in a few tens of nanometers thick, Pb‐free CaTiO3 films are demonstrated. Due to the competition between interfacial and bulk energies, as film thickness increases, epitaxial CaTiO3 films exhibit a ferroelectric‐to‐paraelectric phase transition that is concomitant with the rhombohedral‐to‐orthorhombic structural transition. This so‐called thickness‐driven morphotropic phase transition (MPT) in nanoscale CaTiO3 films stems from the metastable nature of ferroelectricity. The resulting morphotropic phase boundary at the atomic scale in nanoscale CaTiO3 films is visualized. It is also shown that this thickness‐driven MPT can lead to reasonably good piezoelectricity at the nanoscale. This study highlights the rich phase evolution of complex ferroelectrics as a novel platform to control the functionality of nanoscale electromechanical devices.

Ferroelectric and electrical Investigation of new multifunctional material Sr2BiNbO6 for possible device application

The conventional solid-state reaction route is adopted for the synthesis of new multifunctional material Sr2BiNbO6. X-ray diffraction and scanning electron microscopy techniques confirm its formation in single-phase having monoclinic crystal symmetry with dense surface topography. The phase identification and purity are analyzed using Fourier transform infrared and energy dissipative spectroscopy methods respectively. The optical sensitivity along with calculating the bandgap of the material was done through UV-Visible spectroscopy analysis. The dielectric study was carried out at various temperatures (25–500 °C) and frequencies (1 kHz–5 MHz). The analyses of ferroelectric and transport nature of prepared perovskite are done from P-E, impedance, modulus and conductivity curves. The obtained results from various characterizations signify the usefulness of this new material in modern electronic device applications.

Sodium and potassium ion rich ferroelectric solid electrolytes for traditional and electrode-less structural batteries

The transition to a sustainable society is vital and requires electrification. Sodium and potassium ion-based electrolytes will likely play an important role in energy storage as these elements are very abundant. The latter cations and chloride are especially interesting since life on the planet is somehow based on biological transfers of these ions through cell membranes. K+ is the key charge carrier in plants. Here, we characterize electrochemically, electrostatically, and structurally novel electrolytes, K3ClO and K2.99Ba0.005ClO, and compare their performance with Na3ClO and Na2.99Ba0.005ClO in symmetric and asymmetric structural electrode-less cells, such as K/K2.99Ba0.005ClO in a cellulose membrane/K, Na/Na2.99Ba0.005ClO in a cellulose membrane/Na, Al/K2.99Ba0.005ClO composite/Cu, and Al/Na2.99Ba0.005ClO composite/Cu, at temperatures that range from −45 to 65 °C. An ab initio molecular dynamics structural study followed by band structure determination using density functional theory and hybrid simulations allowed us to compare the amorphous character of the structures, bandgap, and electron localization function for both K3ClO at 25 °C and Na3ClO at 37 °C, temperatures at which preliminary studies indicate that these compounds are already amorphous. As in Na+-based electrolytes, the ferroelectric character of the K+-based electrolytes is well recognizable, especially at −45 °C, where the relative real permittivity achieves 1013 in K/K2.99Ba0.005ClO in cellulose membrane/K symmetric cells for an ionic conductivity of ∼120 mS/cm. As in Na+-based electrodes-less structural battery cells, self-charge and self-cycling phenomena are also demonstrated reinforcing the ferroelectric nature of the A3ClO (A = Li, Na, and K) family of electrolytes. These studies may contribute to understanding the K+ and Na+ transfer behavior in energy harvesting and storage as well as the biologic world.

Enhanced energy storage properties of epitaxial (Ba0.955Ca0.045)(Zr0.17Ti0.83)O3 ferroelectric thin films

Abstract(Ba0.955Ca0.045)(Zr0.17Ti0.83)O3 [BCZT] epitaxial were grown on La0.67Sr0.33MnO3 (LSMO)‐coated (100)‐oriented MgO single crystal substrates by the pulsed laser deposition (PLD) technique. Herein, we report crystal structure, ferroelectric, piezoresponse force microscopy (PFM), and energy storage properties near the morphotropic phase boundary (MPB) composition of [Ba0.850Ca0.15Zr0.1Ti0.90O3] solid solution. Epitaxial growth of the films was confirmed using X‐ray diffraction (XRD) spectra. Room‐temperature Raman spectroscopy confirms perovskite phase of BCZT films. Room‐temperature polarization‐electric field (P‐E) loops confirm the ferroelectric nature of BCZT films. Ferroelectric hysteresis loops demonstrate high saturation polarization (Pmax ~ 97.96 μC/cm2) and remanant polarization (Pr ~ 70.1 μC/cm2) at an applied maximum electric field ~2.77 MV/cm. The optimized BCZT epitaxial thin films have shown moderate dielectric properties at different measured frequencies (10‐100 kHz). Nanoscale piezoresponse force microscopy (PFM) images demonstrate switchable ferroelectric polarization of these thin films above ±9 V of dc voltage applied. Energy storage properties measured from ferroelectric loops revealed a high discharge curve energy density ~27.5 J/cm3 at a maximum electric field of 2.77 MV/cm. Epitaxial‐grown BCZT films are suitable candidate materials for capacitor applications.

High Entropy Oxide Relaxor Ferroelectrics.

Relaxor ferroelectrics are important in technological applications due to strong electromechanical response, energy storage capacity, electrocaloric effect, and pyroelectric energy conversion properties. Current efforts to discover and design materials in this class generally rely on substitutional doping as slight changes to local compositional order can significantly affect the Curie temperature, morphotropic phase boundary, and electromechanical responses. In this work, we demonstrate that moving to the strong limit of compositional complexity in an ABO3 perovskite allows stabilization of relaxor responses that do not rely on a single narrow phase transition region. Entropy-assisted synthesis approaches are utilized to synthesize single-crystal Ba(Ti0.2Sn0.2Zr0.2Hf0.2Nb0.2)O3 [Ba(5B)O] films. The high levels of configurational disorder present in this system are found to influence dielectric relaxation, phase transitions, nanopolar domain formation, and Curie temperature. Temperature-dependent dielectric, Raman spectroscopy, and second-harmonic generation measurements reveal multiple phase transitions, a high Curie temperature of 570 K, and the relaxor ferroelectric nature of Ba(5B)O films. The first-principles theory calculations are used to predict possible combinations of cations to design relaxor ferroelectrics and quantify the relative feasibility of synthesizing these highly disordered single-phase perovskite systems. The ability to stabilize single-phase perovskites with various cations on the B-sites offers possibilities for designing high-performance relaxor ferroelectric materials for piezoelectric, pyroelectric, and electrocaloric applications.

Structural and electrical characteristics of manganese modified Bi0.5K0.5TiO3 ceramic

The Rietveld analysis of X-ray diffraction spectrum confirms the tetragonal (P4bm) symmetry of the manganese doped Bi0.5K0.5TiO3 (BKT) compound synthesized by the solid-state reaction route. The dielectric analysis of doping of 5% manganese (Mn) ions at the Ti-sites in the host BKT is analyzed on the basis of the Maxwell–Wagner mechanism in the material. The P-E loop indicates the ferroelectric nature of the compound. Correlated barrier hopping is found to be the dominant conduction mechanism in the compound. The leakage current confirms the negative temperature coefficient of resistance nature of the compound and the Ohmic electrode contact. The substitutions of smaller Mn ion with multiple valencies at the Ti site enhances the dielectric constant substantially, decreases the loss tangent, and lower the leakage current. These features are applicable for energy storage devices, memory devices, high-temperature sensors, and high-temperature capacitors.

Structural, microstructural and electrical characteristics of Ca, Sn and Se modified Bi0.5Na0.5TiO3 ferroelectric ceramics

In this paper, studies of structural, microstructural and electrical properties of calcium, tin, and selenium modified bismuth sodium titanate (Bi0.5Na0.5TiO3) compound with a general chemical formula (Bi0.45Na0.45Ca0.1) (Ti0.9Sn0.05 Se0.05) O3, synthesized by a high-temperature mixed oxide reaction method, have been discussed. Analysis of room temperature X-ray diffraction data confirms the formation of perovskite single-phase compound with rhombohedral symmetry. The surface morphology of the sample exhibits the uniform distribution of grains of varying size. Studies of the electrical parameters (dielectric, impedance and conductivity) of the material, collected at various temperatures (75–375 °C) in a wide frequency range (1 kHz–1MHz) have provided its conduction and relaxation behavior. The electric field dependent current density (J-E) characteristics suggest the Ohmic behavior while the field dependent polarization (P-E loop) confirms the ferroelectric nature of the studied material.