Properties Of Ferroelectric Materials Research Articles

Ferroelectric-relaxor boundary in La-modified Pb(Mg1/3Nb2/3)O3-xPbTiO3 crossover showing enhanced dielectric and piezoelectric properties

The dielectric and piezoelectric properties of La-modified Pb(Mg1/3Nb2/3)O3-xPbTiO3 crossover ceramics were systematically studied. In this crossover region, there is a ferroelectric-relaxor boundary separating the ferroelectric and relaxor states, which is determined by the spontaneous transition from relaxor to ferroelectric state with decreasing temperature. At the ferroelectric-relaxor boundary, the maximum permittivity increases from 18,200 to 23,500, and piezoelectric coefficient (d33) increases from 300 pC/N to 450 pC/N accompanied by the electrostrain improved from 0.09% to 0.12%, as compared with adjacent ferroelectric specimen. These enhancements may originate from the low energy barrier for polarization rotation induced by the existence of spontaneous transition and the coexistence of macrodomain and polar nanodomain configuration. This work indicates that the ferroelectric-relaxor boundary in crossover region may become an effective approach to enhance the dielectric and piezoelectric properties of ferroelectric materials.

Estimation of Ferroelectric Material Properties and Phase-Shifter Design Key Parameters Influence on Its Figure of Merit for Optimization of Development Process

A model of the estimation of the ferroelectric-based phase-shifter figure of merit concerning the material properties and phase-shifter design parameters is presented. The influence of ferroelectric material tunability and losses on phase-shifter characteristics are analyzed. Two approaches to phase-shifter design (transmission line and band-pass filter) are considered. The review of the published results on the ferroelectric phase-shifter design was performed to approve the method proposed. Recommendations to optimize the phase-shifter development process are suggested on the basis of the elaborated model and analysis performed.

Structural and dielectric properties of pure potassium sodium niobate (KNN) lead free ceramics

Lead free KNN (K0·5Na0·5NbO3) ceramics was obtained via the conventional solid state sintering technique. The ceramics synthesized was characterized for their phase transition analysis, crystal structure, morphology and electrical properties. The powder X-ray diffraction (XRD) patterns confirmed single phase of KNN with orthorhombic crystal system at room temperature. Scanning electron microscopy (SEM) of the sintered KNN revealed the existence of densification and comparable size of the grains. Two phase transitions were observed in ϵr-T graph: orthorhombic to tetragonal at TO-T (~236 °C) and tetragonal to cubic at TT-C (~440 °C) for 1 kHz frequency. The decrease in the net polarization of the material with the increase in frequency leads to the decrease in the value of ϵr and tanδ. Three characteristic Raman peaks observed at (~262 cm−1, ~617 cm−1 and ~858 cm−1) correlate the structure and ferroelectric properties of KNN materials. These promising outcomes demonstrate that KNN-based lead-free ceramic composition is potential candidate to substitute lead-based materials for various applications.

Effect of LaNiO3 interlayer on electrical properties of Pb(Zr0.52Ti0.48)O3/LaNiO3/Pb(Zr0.52Ti0.48)O3 composite films

In this study, Pb(Zr0.52Ti0.48)O3/LaNiO3/Pb(Zr0.52Ti0.48)O3 (PZT/LNO/PZT) composite films with different LNO thicknesses were prepared by a sol-gel method. The influences of LNO interlayer on crystalline structure, microstructure and electrical properties of PZT/LNO/PZT composite films were studied. The results show that the perovskite grains of the upper PZT layer grow along the epitaxy of the LNO interlayer when the LNO layer is inserted into the composite films. Due to the in-plane compressive strain effect in the upper PZT layer and the reduced leakage current caused by the accumulated space charges at the PZT/LNO interface, an obvious enhancement of electrical properties is observed in PZT/LNO/PZT composite films. The PZT/LNO/PZT composite film with the 140-nm-thick-LNO layer possesses the best remnant polarization and dielectric constant, which are 43.3 μC cm−2 and 1841, respectively. The preparation of ferroelectric composite film with a ferroelectric/metallic oxide/ferroelectric structure provides a promising way for improving the electrical properties of ferroelectric materials.

Machine learning identified materials descriptors for ferroelectricity

With aid of good materials descriptors, machine learning algorithms are able to accelerate the design of new materials and uncover underlying mechanisms. In the present study, we adopt machine learning methods to discover the most important materials descriptors for properties of ferroelectric materials. A regression study, in typical BaTiO3-based and K1/2Na1/2NbO3-based lead-free ceramics and lead-contained PbMg1/3Nb2/3TiO3-PbTiO3 ceramics, screens out three important materials descriptors determining ferroelectricity from 46 potential descriptors. The three descriptors of Matyonov-Batsanov electronegativity, ratio of valence electron number to nominal charge and core electron distance (Schubert) are confirmed to be dominant as well in classification of perovskite compounds into antiferroelectrics or not. The classification based on these descriptors exhibit an excellent accuracy of 96%, much higher than that of traditional criterion (89%) using tolerance factor and Pauling electronegativity. Furthermore, we propose a machine learning strategy based on our descriptors to predict the phase coexistence. The prediction probability after bootstrapping provides an effective approach to distinguish the phase boundaries and predict the phase ratio of coexisted phases. In all, we identified materials descriptors for ferroelectric materials, which is helpful to reveal the structure-property relationship of ferroelectric materials and guide the design of better ferroelectricity and piezoelectricity.

Theoretical prediction of size and dimension dependent critical temperature for ferroelectric, ferromagnetic and superconductive nanomaterials

In this study, interface energy and internal energy are used to characterize the contribution of the interface lattice and internal lattice to the phase transition of nanomaterials, respectively. And the equivalence principle of interface energy and internal energy is defined. According to the above assumptions, a novel theoretical model without any fitting parameters is established to quantitatively characterize the influence of size on the critical transition temperature of nanomaterials. A good agreement between the predicted results of our model and the available experimental results of ferroelectric, ferromagnetic and superconductive nanomaterials is obtained. The quantitative relationship between the size dependent critical temperature, melting enthalpy, melting point and atomic diameter is uncovered by the present model. Particularly, compared with the existing models, our model can more reasonably predict the change trend that the critical temperature decreases rapidly with the increase of the size when the size is less than a certain minimum value, and increases with the increase of the size when the size is larger than the value. Moreover, our model can reasonably predict the critical size at which ferroelectric properties of ferroelectric materials disappear. This study provides a convenient and practical method to further explore the change law of critical temperature with size.

Compositional and phase dependence of elastic modulus of crystalline and amorphous Hf1-xZrxO2 thin films

The elastic moduli of amorphous and crystalline atomic layer-deposited Hf1-xZrxO2 (HZO, x = 0, 0.31, 0.46, 0.79, 1) films prepared with TaN electrodes on silicon substrates were investigated using picosecond acoustic measurements. The moduli of the amorphous films were observed to increase between 211 ± 6 GPa for pure HfO2 and 302 ± 9 GPa for pure ZrO2. In the crystalline films, it was found that the moduli increased upon increasing the zirconium composition from 248 ± 6 GPa for monoclinic HfO2 to 267 ± 9 GPa for tetragonal ZrO2. Positive deviations from this increase were observed for the Hf0.69Zr0.31O2 and Hf0.54Zr0.46O2 compositions, which were measured to have moduli of 264 ± 8 GPa and 274 ± 8 GPa, respectively. These two compositions contained the largest fractions of the ferroelectric orthorhombic phase, as assessed from polarization and diffraction data. The biaxial stress states of the crystalline films were characterized through sin2(ψ) x-ray diffraction analysis. The in-plane stresses were all found to be tensile and observed to increase with the increasing zirconium composition, between 2.54 ± 0.6 GPa for pure HfO2 and 5.22 ± 0.5 GPa for pure ZrO2. The stresses are consistent with large thermal expansion mismatches between the HZO films and silicon substrates. These results demonstrate a device-scale means to quantify biaxial stress for investigation on its effect on the ferroelectric properties of hafnia-based materials.

In-plane polarization contribution to the vertical piezoresponse force microscopy signal mediated by the cantilever “buckling”

Rigorous experimental/theoretical approach to measure and to minimize in-plane piezoresponse contribution to the vertical piezoresponse force microscopy (PFM) signal is presented. In-plane piezoresponse mediated by the cantilever “buckling” is shown to affect apparent vertical PFM signal being of the same order of magnitude as a true out-of-plane piezoresponse. Decoupling of these two contributions based on simple mathematical procedure is demonstrated. Row PFM data are analyzed as a function of the laser beam focus position on the cantilever allowing suppression of “buckling” contribution and, hence, measurement of only out-of-plane piezoresponse component. This approach can be used for the accurate recovery of the piezoresponse displacement vector, what is of paramount importance for the reconstruction of the domain structures and quantitative characterization of the polarization distribution and local piezoelectric properties in ferroelectric materials.

Changes of dielectric and ferroelectric properties of functional materials under external electric field and compressive stress

This review summarizes the seminal work on the influence of the external stimuli on the dielectric and ferroelectric properties of some technologically important functional materials in the past two decades. These works reflect the important studies of how the external applied electric field and mechanical stress of the properties of materials. In addition to some works by prior important pioneers, the review pointed out several works from our previous investigations on scaling behaviors, in which the effects of field frequency and magnitude were studied in PZT- and BaTiO3-based single crystals and ceramics. The influence of the compressive stress on dielectric and ferroelectric properties of prototypic functional materials was also examined and summarized. In summary, the external stimuli were found to show significant influence on the important properties of these functional materials.

Atomic-Scale Domain Mediation in Nd-Doped BiFeO3 Film

A large number of applications involving ferroelectric materials are substantially influenced by domain walls (DWs). Especially, charged DWs (CDWs) show great potentials in controlling the switching mechanism and the electric and piezoelectric properties of ferroelectric materials. In the present 5% Nd-doped BiFeO3 film, besides the uniformly downward polarization in the film matrix, special domain configurations including 71° CDW and the adjacent inserting nanodomain as well as the resulting DW junction near the film surface have been quantitatively resolved by aberration-corrected scanning transmission electron microscopy. Direct polarization mapping of DWs combined with the unit-cell-wise strain map at an atomic scale demonstrate the accumulation of Nd at the CDWs. The favorable formation of the observed local domain configurations depends on the minimization of the total DW energy and the screening of bound charges accumulated at the local surface of the film.

Study of changes in the crystal structure of BaTiO<sub>3</sub> under the effect of X-ray radiation

X-ray diffractometers are widely used in studying the atomic structure of mono- and polycrystalline substances. The radiation source of conventional laboratory diffractometers is a soldered x-ray tube with the maximum power consumption 1 – 3 kW. The radiation spectrum of the tube is determined by the anode material (usually, these are spectrally pure metals Cr, Ni, Fe, Cu, Mo, Ag). The wavelengths of the characteristic radiation range within 0.56 – 2.29 Е . We present the results of studying the effect of X-ray radiation power on the structure of barium titanate. Comparison of the diffraction spectra of BaTiO 3 (laminar polydomain ferroelectric single crystal and nanopowder samples) showed that the spectrum structure changes significantly with an increase in the power of X-ray beam (Cu K α radiation) from 100 (5 mA, 20 kV) to 800 W (20 mA, 40 kV). For example, a rearrangement of the domain structure and, hence, a change in the dielectric characteristics of the material were observed for BaTiO 3 single crystal. The rearrangement was accompanied by the formation of continuous transition zones (between domains) containing a cubic phase. As for the BaTiO 3 nanopowder, a change in the structure was observed in the direction of the axis of spontaneous polarization c and an invariance of the structure in the plane a – c . The results obtained can be used to control the physical properties of ferroelectric and ferroelastic materials, in particular, the memristor characteristics of epitaxial films based on YBa 2 Cu 3 O 7– δ due to changes in their twin structure under X-ray irradiation.

Tailoring and improving the strong-electric-field electrical properties of the BNT-BT ferroelectric ceramics by a functional-group-doping

Lead-free ferroelectric ceramics with high tailored strong-electric-field electrical properties (energy storage, electrocaloric cooling, and energy harvesting, etc.) are attractive to many fields, such as modern electronics, medical and military, etc. We demonstrated that the strong-electric-field electrical properties of the 0.89(Bi0.5Na0.5TiO3)-0.11(BaTiO3) (BNT-BT) relaxor ceramics not only could be tailored easily after doping the (BaTiO3)0.5-(BiMg0.5Ti0.5O3)0.5 (BT-BMT, the functional-group), but also could be improved largely. As a result, an optimized electrostrain (S ~ 0.4%) was acquired at x = 0.12, and an optimized energy storage density (W ~ 0.775 J/cm3) with a high efficiency (η ~ 50%) was achieved at x = 0.24, as well as a phase-induced negative electrocaloric (EC) effect (ΔT ~ 3.72 K) was harvested at x = 0.04. It is concluded that the functional-group-doping can be regarded as a new strategy to tailor and improve the strong-electric-field electrical properties of ferroelectric materials.

Biferroic properties in Co-doped 0.2BaZrO3-0.8BaTiO3 materials

Combination in both ferroic properties in current lead-free ferroelectric materials is promising in creating a new type of smart electronic devices. In this report, single perovskite Co-doped 0.2BaZrO3-0.8BaTiO3 materials were synthesized by using the chemical method. The random incorporation of Co cations into the host lattice of 0.2BaZrO3-0.8BaTiO3 compounds resulted in distortion of the lattice parameter and strong reduction the optical band gap energy. Decreasing optical band gap energy was obtained from around 3.17 to 2.52 eV by introducing Co concentration of up to 9 mol.%. The magnetic properties of 0.2BaZrO3-0.8BaTiO3 compounds were showed in complex as dependent on the level of Co dopants. The nonlinear electrical polarization in 0.2BaZrO3-0.8BaTiO3 compounds was obtained and remained after the introduction of Co impurities. The observation in nonlinear in magnetism and electrical polarization were promised to transfer their materials for device applications.

The effect of Ba/Sr ratio on the Curie temperature for ferroelectric barium strontium titanate ceramics

The powders of lead-free material namely (nonhazardous) barium strontium titanate (BST) with different stoichiometric compositions have been synthesized by the sol–gel method. Ba[Formula: see text]Sr[Formula: see text]TiO3 (BST) materials possess the properties of both ferroelectric and dielectric materials. These materials have spontaneous polarization that can be reversed by an applied electric field and they remain polarized even when the applied external electric field is removed. Synthesized samples have been subjected to structural, morphological, and dielectric characterizations. In this study, BST nanopowders with different substitutions of [Formula: see text] (where [Formula: see text]= 0.2, 0.3, 0.4, 0.5, and 0.6) were prepared by the sol–gel method, which is an easy method with low power consumption and low temperature requirement and produces higher yield. Nanopowders had average particle sizes of 12–24 nm and particles sizes after sintering at 1000[Formula: see text]C for 3 h were 197, 267, 79.80, 63.09, and 63 nm. All resulting pellets had a polycrystalline structure. Crystal structure, space group, morphological characterization, and particle size were determined from the structural analysis using X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The dielectric measurements were made for BST pellets under different frequencies (1–200 kHz) from room temperature to 250[Formula: see text]C. The dielectric constants for the bulk were 743, 1566, 1091, 766, and 626 for [Formula: see text]= 0.2, 0.3, 0.4, 0.5, and 0.6, respectively. From dielectric measurements, samples with [Formula: see text]= 0.2 and 0.3 had the Curie temperatures of 70[Formula: see text]C and 28.5[Formula: see text]C, respectively, and remained intact below 0[Formula: see text]C. The sample with [Formula: see text]= 0.3 had a good dielectric measurement and moderate dissipation factor; it may be used in capacitance application as energy stores.

Tracking ferroelectric domain formation during epitaxial growth of PbTiO3 films

The arrangement of domains and domain walls is a crucial factor in determining the functional properties of ferroelectric materials. Here, we track the ferroelectric domain formation mechanism in ultrathin PbTiO3 films in real time during epitaxial growth using in situ optical second harmonic generation. In combination with complementary ex situ piezoresponse force microscopy and second harmonic generation imaging, we unambiguously identify the tensile-epitaxial-strain-induced partial conversion of out-of-plane-polarized c-domains into in-plane-polarized a-domains. We further show that, in the strongly compressive epitaxial regime, the c-to-a conversion can be shifted to the early stage of the growth to favor a remarkable randomization in the distribution of a- and c-domains. This unprecedented access to the domain-formation dynamics constitutes an important step toward deterministic domain architectures in technologically relevant ultrathin ferroelectrics which, in turn, is valuable for the development of functional ferroelectric and piezoelectric structures.

Photo-degradation organic dyes by Sb-based organic-inorganic hybrid ferroelectrics

The organic-inorganic hybrid halide compounds have emerged as one of the most promising photoelectric material for their superior optoelectronic properties and hold great prospects for renewable energy substitutes and environmental protection as photocatalysis. Here, we report the optical properties of the Sb-based organic-inorganic hybrid ferroelectric materials: pyridine-4-aminium tetrachloroantimonate ((C5H7N2)SbCl4, sample 1), piperidin-1-aminium tetrachloroantimonate ((C5H13N2)SbCl4, sample 2) and tris(trimethylammonium) nonachlorodiantimonate (((CH3)3NH)3Sb2Cl9, sample 3), which are a kind of exploited efficient photocatalysts. Samples 2 and 3 exhibit distinct photoelectric respond, which are mainly ascribed to their minor narrow band-gap compared with sample 1. For the ferroelectrics, the intrinsic of spontaneous polarization of sample 3 at room temperature is favourable for the separation of photogenerated electrons and holes within the photorespond process. Moreover, sample 3 shows the highest efficiency of photo-decomposed Rhodamine B (90.2% within 80 min) and Methyl Orange (MO) (97.4% within 50 min), thanks to the photo-excited electrons and holes promoting the formation of oxidative radical species during the photo-redox progress. These findings prove that the development of a novel Sb-based organic-inorganic hybrid halide compounds with good stability in the degradation of organic dyes paves a way to designing new photocatalyst.

In brief

PAGE 810 Greek and Serbian researchers present a new recurrent neural network (RNN) for solving linear algebraic systems with finite-time convergence. The network can converge on a solution faster than previous methods due to inclusion of an exponential term in the Zhang neural network (ZNN). The work is validated by theoretical analysis and simulation. PAGE 816 Two researchers from South Korea introduce attention-guided domain adaptation networks for face recognition under an unsupervised setting. The proposed module is applied to category classifiers and domain discriminators in a channel-wise manner. By learning the optimal adaptation factor for each channel the networks successfully align source and target domains. The residual error ||Ax(t)−b||of VPFTZNN (5) (for γ= 100,p= 3 and q= 2) and GNN [12]. PAGE 840 A capacitor-based bionic synapse is proposed, harnessing the partial polarisation switching of multi-domain properties in polycrystalline Zr-doped HfO2 ferroelectric materials. The synapse shows multi-level capacitance modulation characteristics. This research lays the groundwork for realising high-density integration neuromorphic computing systems. Proposed attention-guided model. PAGE 806 Chinese researchers propose a time-difference integrator which can compensate for the time-error caused by leakage current in gated delay-buffer cells. It is implemented in a 28-nm CMOS process, achieving a gain of 27.39 dB with a 317 kHz 30 ps peak-to-peak sinosudal input and consumes 110.3 μW with 50 MHz sampling rate from a 0.9 V supply. Simplified schematic of the prepared capacitor with TiN/HZO/TiN structure. PAGE 808 Two researchers from New Zealand present the design and analysis of a tunable low-noise amplifier, capable of achieveing single-band (1 GHz), dual-band (1 GHz and 1.7 GHz–2.5 GHz) and wideband (1.6–2.5 GHz) operations. The amplifier has a measured power gain of 7–15 dB and a noise figure of 1.2–2.2 dB across all bands. Simulated integrated time error. Multimode tunable low-noise amplifier design.

Recent Progress in the Nanoscale Evaluation of Piezoelectric and Ferroelectric Properties via Scanning Probe Microscopy.

Piezoelectric and ferroelectric materials have garnered significant interest owing to their excellent physical properties and multiple potential applications. Accordingly, the need for evaluating piezoelectric and ferroelectric properties has also increased. The piezoelectric and ferroelectric properties are evaluated macroscopically using laser interferometers and polarization–electric field loop measurements. However, as the research focus is shifted from bulk to nanosized materials, scanning probe microscopy (SPM) techniques have been suggested as an alternative approach for evaluating piezoelectric and ferroelectric properties. In this Progress Report, the recent progress on the nanoscale evaluation of piezoelectric and ferroelectric properties of diverse materials using SPM‐based methods is summarized. Among the SPM techniques, the focus is on recent studies that are related to piezoresponse force microscopy and conductive atomic force microscopy; further, the utilization of these two modes to understand piezoelectric and ferroelectric properties at the nanoscale level is discussed. This work can provide guidelines for evaluating the piezoelectric and ferroelectric properties of materials based on SPM techniques.

Consistent and Efficient Modeling of the Nonlinear Properties of Ferroelectric Materials in Ceramic Capacitors for Frugal Electronic Implants

In recent years, the development of implantable electronics has been driven by the motivation to expand their field of application. The main intention is to implement advanced functionalities while increasing the degree of miniaturization and maintaining reliability. The intrinsic nonlinear properties of the electronic components, to be used anyway, could be utilized to resolve this issue. To master the implementation of functionalities in implantable electronics using the nonlinear properties of its electronic components, simulation models are of utmost importance. In this paper, we present a simulation model that is optimized in terms of consistency, computing time and memory consumption. Three circuit topologies of nonlinear capacitors, including hysteresis losses, are investigated. An inductively coupled measurement setup was realized to validate the calculations. The best results were obtained using the Trapezoid method in ANSYS with a constant step size and a resolution of 500 k points and using the Adams method in Mathcad with a resolution of 50 k points. An inductive coupling factor between 7% and 10% leads to a significant improvement in consistency compared to lower coupling factors. Finally, our results indicate that the nonlinear properties of the voltage rectifier capacitor can be neglected since these do not significantly affect the simulation results.

Growth and magnetic properties of new lead-free (1 − x)Bi1/2Na1/2TiO3 + xBi(Ti1/2Co1/2)O3 solid solution materials

The new solid solution system of (1 − x)Bi1/2Na1/2TiO3 + xBi(Ti1/2Co1/2)O3 materials was fabricated using the sol–gel method. The structural studies via X-ray diffraction and Raman scattering indicated that Bi(Ti1/2Co1/2)O3 materials were well dissolved into host Bi1/2Na1/2TiO3 materials to follow the rhombohedral structure of host materials. The diffuse cations of Bi(Ti1/2Co1/2)O3 to random incorporation with host lattice to form as solid solution in host Bi1/2Na1/2TiO3 materials resulted in distortion lattice parameter and reduced the optical band-gap values from 3.06 to 2.32 eV for pure and 9 mol% Bi(Ti1/2Co1/2)O3 solute into host Bi1/2Na1/2TiO3 materials. The compensative diamagnetism and weak ferromagnetism of pure Bi1/2Na1/2TiO3 materials were tuned to ferromagnetism at room temperature as increasing the Bi(Ti1/2Co1/2)O3 amounts solute into host Bi1/2Na1/2TiO3 materials. The observation of the room-temperature ferromagnetism in Bi(Ti1/2Co1/2)O3-modified Bi1/2Na1/2TiO3 system was important to integrate the ferromagnetic properties in lead-free ferroelectric materials for further application in smart electronic devices which were required multifunctional materials.