Irreversible Domain Wall Motion Research Articles

Exploring the mechanisms of enhanced piezoelectric properties in (K,Na)NbO3 single crystals

(K,Na)NbO3 (KNN)-based piezoelectric materials are candidates for replacing Pb-based materials. However, the piezoelectric properties of existing KNN-based single crystals are still inferior to those of Pb-based relaxor ferroelectric single crystals. Moreover, the piezoelectric response mechanism of KNN-based single crystals remains unclear. In this study, (Li,K,Na)(Nb,Sb,Ta)O3:Mn (KNNLST:Mn) single crystals with an excellent piezoelectric coefficient d33 of approximately 778 pC/N were prepared. Systematically studies of intrinsic and extrinsic piezoelectric responses have revealed that the high d33 of KNNLST:Mn single crystals is related to the shear piezoelectric response of a single-domain state and irreversible domain wall motion of the engineering domains. Furthermore, the effect of the orthorhombic (O)-tetragonal (T) phase boundary on intrinsic and extrinsic piezoelectric response is systematically studied, and the impact mechanism is elucidated. The results indicate that a lower dielectric response and elastic constant limit the intrinsic shear piezoelectric response of KNNLST:Mn single crystals, and approaching the O–T phase boundary can enhance both intrinsic and extrinsic piezoelectric responses. This study improves our understanding of the structure-performance relationship in KNN-based single crystals and offers insights for optimizing piezoelectric properties in KNN-based materials.

High magneto-mechanical hysteresis-type damping in FeGaMo alloys

Optimization of the damping capacity of conventional FeCr-based ferromagnetic high damping alloys (HDAs) usually involves a trade-off in terms of degradation of mechanical properties due to grain coarsening caused by high-temperature annealing. In this work, new ferromagnetic HDAs of FeGaMo alloys with different Mo contents are reported, which can exhibit high damping when treated in a medium temperature range. Among these alloys, the alloy with Mo content of 2 at% exhibits the best damping capacity of 4.20 × 10−2 (Q−1, equivalent to a special damping capacity SDC of 0.26). It is found that the Mo element has a high solid solubility in the FeGa alloy, and when the Mo content is 2 at%, only isolated tiny precipitations are observed in the matrix. These small precipitates have a negligible effect on hindering domain motion, and the corresponding coercivity change is extremely weak compared to the Mo-free FeGa alloy. As the Mo content increases to 4 at% or 6 at%, Mo-rich phases precipitate within the grains and along the grain boundaries, resulting in an increasing coercivity. Interestingly, as the Mo content increases, the domain density in the (001) and (110) surfaces gradually increases and the arrangement of magnetic domains becomes more tortuous due to the decrease in the magnetocrystalline anisotropy constant. For the FeGaMo alloy with 2 at% Mo content, the high damping capacity mainly arises from the energy loss caused by the high density of irreversible motion of domain walls (DWs) under the applied stress, and as the Mo content continues to increase, the significant precipitation of Mo-rich phases severely restricts the movement distance of DWs, leading to a decrease in damping. This work provides valuable insights for the design and research of new ferromagnetic high damping materials in the future.

Role of polarization evolution in the hysteresis effect of Pb-based antiferroelecrtics

The electric field-induced irreversible domain wall motion results in a ferroelectric (FE) hysteresis. In antiferroelectrics (AFEs), the irreversible phase transition is the main reason for the hysteresis effects, which plays an important role in energy storage performance. Compared to the well-demonstrated FE hysteresis, the structural mechanism of the hysteresis in AFE is not well understood. In this work, the underlying correlation between structure and the hysteresis effect is unveiled in Pb(Zr,Sn,Ti)O3 AFE system by using in-situ electrical biasing synchrotron X-ray diffraction. It is found that the AFE with a canting dipole configuration, which shows a continuous polarization rotation under the electric field, tends to have a small hysteresis effect. It presents a negligible phase transition, a small axis ratio, and electric field-induced lattice changing, small domain switching. All these features together lead to a slim hysteresis loop and a high energy storage efficiency. These results offer a deep insight into the structure-hysteresis relationship of AFEs and are helpful for the design of energy storage material.

Effect of Acoustic Oscillations on Non-Equilibrium State of Magnetic Domain Structure in Cubic Ni2MnGa Single Crystal.

Magnetic hysteresis is a manifestation of non-equilibrium state of magnetic domain walls trapped in local energy minima. Using two types of experiments we show that, after application of a magnetic field to a ferromagnet, acoustic oscillations excited in the latter can "equilibrate" metastable magnetic domain structure by triggering the motion of domain walls into more stable configurations. Single crystals of archetypal Ni2MnGa magnetic shape memory alloy in the cubic phase were used in the experiments. The magnetomechanical absorption of ultrasound versus strain amplitude was studied after step-like changes of a polarizing magnetic field. One-time hysteresis was observed in strain amplitude dependences of magnetomechanical internal friction after step-like variations of a polarizing field. We distinguish two ingredients of the strain amplitude hysteresis that are found in the ranges of linear and non-linear internal friction and show qualitatively different behavior for increasing and decreasing applied polarizing fields. The uncovered effect is interpreted in terms of three canonical magnetomechanical internal friction terms (microeddy, macroeddy and hysteretic) and attributed to "triggering" by acoustic oscillations of the irreversible motion of domain walls trapped in the metastable states. To confirm the suggested interpretation we determine the coercive field of magnetization hysteresis through the measurements of the reversible Villari effect. We show that the width of the hysteresis loops decreases when acoustic oscillations in the non-linear range of domain wall motion are excited in the crystal. The observed "equilibration" of the magnetic domain structure by acoustic oscillations is attributed to the periodic stress anisotropy field induced by oscillatory mechanical stress.

Enhancing Electromechanical Properties of PZT-Based Piezoelectric Ceramics by High-Temperature Poling for High-Power Applications.

Defect engineering is a proven method to tune the properties of perovskite oxides. In demanding high-power piezoelectric ceramic applications, acceptor doping is the most effective method to harden ceramics, but it inevitably degrades the ceramics' electromechanical properties. Herein, a poling method based on acceptor doping, namely, high-temperature poling, is implemented by applying an electric field above the Curie temperature for poling to achieve a balance of the properties of piezoelectric coefficient d33 and mechanical quality factor Qm. After high-temperature poling, the piezoelectric property of 0.6 mol % Mn-doped Pb0.92Sr0.08(Zr0.533Ti0.443Nb0.024)O3 is d33 = 483 pC/N and Qm = 448. Compared with the traditional poling, the piezoelectric coefficient d33 of the high-temperature poling ceramics increased by approximately 40%, and Qm also increased by nearly 18%. Therefore, high d33 and Qm were exhibited by our PZT piezoelectric ceramics. Rayleigh's law analysis, XRD, and transmission electron microscopy analysis show that, after high-temperature poling, the considerably increased d33 is related to the large increase in the reversible domain wall motion in the intrinsic effect, while the slightly increased Qm is related to the inhibited irreversible domain wall motion in the extrinsic effect. This study reports a method for high-temperature poling and provides insights into the design of high-power piezoelectric ceramics with high d33 and Qm.

Sb2O3‐modified lead zirconate titanate piezoelectric ceramics with enhancing piezoelectricity and low loss

AbstractLead zirconate titanate (PZT)–based piezoelectric ceramics as important functional materials are widely used in many electromechanical devices. The piezoelectric coefficient and mechanical quality factor are vital property parameters for piezoelectric applications. However, the piezoelectric coefficient is inversely proportional to the mechanical quality factor, resulting in a strong limitation among wide applications. Herein, piezoelectric ceramics composed of (xSb2O3, 0.3‐wt% MnCO3)‐doped (Pb0.92Sr0.08)(Zr0.533Ti0.443Nb0.024)O3 ((xSb, Mn)‐PSZTN) were prepared by a conventional solid‐state process. The excellent piezoelectric properties d33 = 554 pC/N, kp = 0.645, and high mechanical quality factor Qm = 540 were simultaneously obtained at x = 0.1 ceramic in the morphotropic phase boundary region. The enhancement of piezoelectric properties was mainly due to the contribution of irreversible domain wall motion. In particular, the regulation of different defect chemical reactions on the properties showed that Sb2O3 could play the role of both donor and acceptor dopant. This work demonstrated that (0.1Sb, Mn)‐PSZTN ceramic was a good candidate material for high‐power piezoelectric devices.

Barkhausen noise emission of AISI 304 stainless steel originating from strain induced martensite by shot peening

This study deals with magnetic Barkhausen noise emission produced by strain-induced martensite generated during shot peening of austenitic AISI 304 stainless steel. The transformation from the paramagnetic to ferromagnetic state and the corresponding birth of the magnetic domain structure are important with respect to irreversible motion of domain walls and the corresponding Barkhausen noise emission. Barkhausen noise is investigated and explained with respect to the residual stress state as well as the microstructure expressed in terms of the martensite fraction, its crystallite size, preferred orientation, surface topography, and microhardness. The strength of the Barkhausen noise is mainly linked with the number of shot peening cycles, corresponding Almen intensity, and the associated volume fraction of strain-induced martensite as well as the extent of its depth. The role of the residual stress state in the martensite phase is minor. Surface strengthening expressed in terms of the microhardness in the near-surface region is very high for the medium shot peening intensity. A remarkable decrease in the near-surface microhardness as well as the presence of heavily thinned folds indicate over shot peening and surface microcracking in the case of a longer shot peening time and the corresponding higher Almen intensity.

Importance of uniformity of grain size to reduce dc degradation and improve reliability of ultra-thin BaTiO3-based MLCCs

Excellent direct current (dc)-bias and reliability have become increasingly important for ultra-thin BaTiO3-based multilayer ceramic capacitors (MLCCs). Herein, X5R-MLCCs with a thickness of ∼1 μm are fabricated using BaTiO3 with varied grain size. It is shown that the uniformity of the grain size plays an important impact on the direct current (dc)-bias and the reliability of ultra-thin MLCCs. Uniform grain size, which is indicative of good distribution of doping element contributes to improved temperature stability. By contrast, abnormal large grains induce reinforced space charge polarization. Chips with non-uniform grains exhibit dramatic dielectric constant change under dc-bias due to the high tetragonality and irreversible domain-wall motion. Weibull distribution and highly accelerated life test (HALT) reveal that non-uniform grains contain more oxygen vacancies supported by impedance spectra analysis at 300–450 °C. This study provides a feasible strategy to improve the dc-bias and the reliability of the ultra-thin MLCCs.

Temperature dependence of dielectric properties and domain structure of (K,Na)(Nb,Ta)O3 single crystal

In this work, the influence of temperature on phase structure, dielectric property and domain structure of (K,Na)(Nb,Ta)O3 (KNNT) crystal from 20 to 200 °C was studied. The irreversible domain wall motion of single crystal is strongest at phase transition temperature by Rayleigh analysis of dielectric properties. The domain structure in the heating and cooling process of single crystal was observed by means of piezoelectricity microscope. The domain structure changed obviously with temperature and the domain structure change is particularly prominent at the phase transition temperature.

Nonlinearity in inverse and transverse piezoelectric properties of Pb(Zr0.52Ti0.48)O3 film actuators under AC and DC applied voltages

The motion of domain walls is a crucial factor in piezoelectric properties and is usually related to the irreversible and hysteretic behaviors. Herein, we report on the investigation of inverse and transverse piezoelectric coefficients of capacitor-based and microcantilever-based Pb(Zr0.52Ti0.48)O3 films with a change in the DC bias and the AC applied voltage. A large inverse piezoelectric strain coefficient of about 350 p.m./V, and a low strain hysteresis of about 7.1%, are achieved in the film capacitors under a low applied voltage of 2 V (20 kV/cm) which can benefit the actuators for motion control in high-precision systems. The field-dependences of the transverse piezoelectric coefficients, obtained from four-point bending and microcantilever displacement, are in good agreement with each other. The results also reveal that the irreversible domain-wall motion is attributed to the nonlinearity in the field-dependent piezoelectric strain and cantilever displacement.

Wake-up and fatigue mechanisms in ferroelectric Hf0.5Zr0.5O2 films with symmetric RuO2 electrodes

The mechanisms leading to wake-up and fatigue in ferroelectric hafnium zirconium oxide thin film devices with symmetric RuO2 electrodes are investigated via polarization, relative permittivity, dielectric nonlinearity, pyroelectric coefficient, and microfocus x-ray diffraction (XRD) measurements. The devices are observed to wake-up for up to 103 bipolar pulsed field cycles, after which fatigue occurs with polarization approaching zero following 108 cycles. Wake-up is accompanied by a decrease in both high-field permittivity and hysteresis loop pinching and an increase in the pyroelectric coefficient, indicating that the wake-up process involves a combination of transformations from the tetragonal to the orthorhombic phase and domain depinning from defect redistribution. Fatigue is observed to coincide with an increase in irreversible domain wall motion and a decrease in pyroelectric coefficient. Finite pyroelectric coefficients are measured on fully fatigued devices, indicating that domain pinning is a strong contributor to fatigue and that fatigued devices contain domain structures that are unable to switch under the fields applied for measurement. Microfocus XRD patterns measured on each device reveal that the phase constitution is qualitatively unaffected by field cycling and resultant polarization fatigue. These data indicate that the wake-up process has contributions from both phase transformations and domain depinning, whereas the fatigue process is driven primarily by domain pinning, and the near-zero measured switchable polarization is actually a poled device with immobile domains. These observations provide insight into the physical changes occurring during field cycling of HfO2-based ferroelectrics while examining a possible oxide electrode material for silicon CMOS device implementation.

Enhanced damping capacity of ferromagnetic Fe-Ga alloys by introducing structural defects

The irreversible motion of magnetic domain walls in ferromagnets can dissipate a large portion of the elastic energy, and the associated damping capacity is proportional to the magnetostriction constant. In contrast, here we found that the damping capacity of the large magnetostriction Fe-Ga alloys can be enhanced by 2–3 times through introducing structural defects including interfacial dislocations and stacking faults, despite that these defects deteriorate the magnetostriction. These structural defects were introduced by aging the BCC (body-centered-cubic) solution-treated precursor, for which the formation of mechanically harder FCT (face-centered-tetragonal) and /or FCC (face-centered-cubic) phases can result in high-density partial dislocations at the semi-coherent phase interfaces and quasi-periodically stacked nano-layer substructure inside the FCC variants. The structural defects act as extra damping sources besides the magnetic domain walls because the structural accommodation of the semi-coherent phase interfaces between BCC and FCT/FCC nanoprecipitates with different elastic moduli and the nano-layer substructure towards long-range ordered periodical stacking can dissipate a large portion of mechanical energy. These findings suggest that introducing structural defects provides fresh freedom to design high damping ferromagnetic materials.

Textured Mn-doped PIN-PMN-PT Ceramics: Harnessing Intrinsic Piezoelectricity for High-power Transducer Applications

Mn-doped PIN-PMN-PT ceramics were 90% [001]C textured by reactive templated grain growth (RTGG) with 5 vol% BaTiO3 microplatelets. Hardened properties such as high coercive field (EC) of 14 kV/cm, low dielectric loss (tan δ) of 0.37-0.66%, and high QM of 496 were obtained. Textured Mn-doped ceramics have TC of 219 °C, and a two times greater low-field d33* of 846 pm/V than random ceramics. Rayleigh analysis of textured PIN-PMN-PT ceramics shows that Mn-doping reduces the relative extrinsic contribution of the piezoelectric response to the strain behavior from 38% to 18% (at 4 kV/cm) by reducing irreversible domain wall motion. Mn-doping also reduced the overall strain response of PIN-PMN-PT, but crystallographic texturing increased the intrinsic piezoelectric response of the lattice as evidenced by the increase in d33 (Berlincourt) from 283 pC/N in random ceramics to 341 pC/N in textured ceramics. These results demonstrate that textured Mn-doped PIN-PMN-PT ceramics are excellent candidates for high-power transducer applications.

Waiting-time statistics in magnetic systems

Many complex systems, from earthquakes and financial markets to Barkhausen effect in ferromagnetic materials, respond with a noise consisting of discrete avalanche-like events with broad range of sizes and durations, separated by waiting times. Here we focus on the waiting-time statistics in magnetic systems. By investigating the Barkhausen noise in amorphous and polycrystalline ferromagnetic films having different thicknesses, we uncover the form of the waiting-time distribution in time series recorded from the irregular and irreversible motion of magnetic domain walls. Further, we address the question of if the waiting-time distribution evolves with the threshold level, as well as with the film thickness and structural character of the materials. Our results, besides informing on the temporal avalanche correlations, disclose the waiting-time statistics in magnetic systems also bring fingerprints of the universality classes of Barkhausen avalanches and a dimensional crossover in the domain wall dynamics.

Reversible and irreversible domain wall dynamics in [011]C oriented relaxor ferroelectric single crystals

AbstractDomain wall motions mainly affect all kinds of properties of ferroelectric materials, such as piezoelectricity, dielectric response, and mechanical loss, and the extrinsic contributions associated with domain wall motions have always been an important issue. In this study, the reversible and irreversible extrinsic contributions to the dielectric properties of [011]C‐oriented 0.27Pb(In1/2Nb1/2)O3‐0.46Pb(Mg1/3Nb2/3)O3‐0.27PbTiO3:Mn single crystals have been extracted by the Rayleigh analysis. We found that in the unpoled samples, the extrinsic contributions of reversible and irreversible domain wall motions to dielectric properties significantly reduced, whereas after poling, only the irreversible extrinsic contribution decreased. The pinning effect in the 2R domain structure is much weaker than that in the 4R domain structure, leading to the low enhancement of Qm and a slight decrease in piezoelectricity caused by acceptor doping in 2R domain structure. This study explores the domain wall dynamics of acceptor‐doped single crystals and mainly guides on further performance optimization in PbTiO3‐based relaxor single crystals.

Nonlinear bilateral caloric–electromechanical couplings in polycrystalline ferroelectrics

AbstractThis research is about irreversible domain wall motion leading to a temperature change of the material. The materials are mostly subjected to high frequencies and large electrical loads, which is why insufficient heat dissipation can lead to undesirable temperature developments, so–called self heating. Predictions concerning polycrystalline material behavior are made by the condensed method.

Damping capacity, magnetic and mechanical properties of Fe-18Cr alloy

Iron-chromium based alloys are known as potentially high damping corrosion-resistance alloys with good mechanical properties and workability. The main structural mechanism of enhanced damping in the Fe-Cr alloys is magneto-mechanical coupling due to reversible and irreversible motion of magnetic domain walls, which is also linked with magnetostriction of the alloys. In order to create new complex alloyed materials with improved functional properties, it is important to study experimentally the basic relation between structure, mechanical and functional properties of binary Fe-Cr alloys. In this paper, we used cold-rolled sheets of a high-purity Fe-18Cr alloy to study the correlation between heat treatment, grain size, damping capacity and magnetostriction. Damping capacity of the samples was measured at bending using forced vibrations by means of dynamical mechanical analyzer Q800 TA Instruments and using free-decay of bending vibrations in different structural states after various annealing treatments. The results show that the optimal properties for Fe-18Cr binary alloy were achieved after annealing of cold-rolled sheets at 840 °C. Homogenizing by annealing at 1200 °C for 3 h before the final heat treatment shifts the annealing temperature for maximal damping capacity to 900 °C with approximately the same value of damping capacity and decreases mechanical properties due to the significant increase in the grain size. Slow cooling of the samples after high-temperature annealing causes a marked decrease of the impact toughness, reduction of damping capacity and an increase in the coercive force of the Fe-18Cr alloy. This effect can be explained by spinodal decomposition of the α-solid solution and formation of local zones enriched with Cr or Fe.

Evaluation of reversible and irreversible domain wall motions in relaxor ferroelectrics: Influence of acceptor ions

The intrinsic, reversible, and irreversible extrinsic dielectric responses of 0.27Pb(In1/2Nb1/2)O3–0.46Pb(Mg1/3Nb2/3)O3–0.27PbTiO3 relaxor single crystals with and without Mn doping have been extracted by using Rayleigh analysis from 0.1 Hz to 1000 Hz, and the influence of acceptor ions has been quantitatively evaluated. The results show that the lattice deformation under an ac electric field is slightly inhibited by Mn2+/Mn3+, while both reversible and irreversible domain wall motions are greatly suppressed to below 20% of the non-Mn doped values. As a result, the mechanical quality factor, which is closely related to domain wall motions, is significantly enhanced. Meanwhile, the large piezoelectricity, which is dominated by intrinsic contribution, is maintained.

Controlled 90° domain wall motion in BaTiO3 piezoelectric ceramics modified with acceptor ions localized near grain boundaries

The irreversible motion of non-180° ferroelectric domain walls is a predominant cause for the increased hysteretic loss in piezoelectric ceramics at elevated temperatures. In this study we designed piezoelectric ceramics modified with acceptor ions localized near grain boundaries for the purpose of suppressing the irreversible domain wall motion at elevated temperatures without diminishing the contribution from the reversible domain wall motion. Particles of undoped BaTiO3 (BT) were coated with Mn-doped BT by a coprecipitation method and then sintered to form a Mn-modified BT ceramic. Structural and dielectric characterizations indicated that the Mn ions in the resulting ceramic were localized near grain boundaries. The measurement of the unipolar electric-field-induced strain was conducted for the Mn-modified and unmodified (pure) BT ceramics at temperatures up to 120 °C (just below the Currie temperature) to discuss the hysteretic behavior in their piezoelectric response. The results showed that the effective piezoelectric coefficient d 33 * of the Mn-modified BT ceramic was comparable to the unmodified BT ceramic. The hysteresis of the Mn-modified BT ceramic was retained below 40% in the whole temperature range whereas that of the unmodified BT ceramic increased significantly at elevated temperatures over 100 °C. The results in this study demonstrate that the localized Mn ions effectively pin the domain walls to suppress their irreversible motion at elevated temperatures, while the reversible motion inside the grains remains possible.

Stress relief by annealing under external stress in Fe-based metallic glasses

The effects of stress relief on the magnetic characteristics of Fe-based metallic glass (MG) ribbons are investigated under external stress through various annealing treatments. We found that long-time annealing treatments benefit for making softer magnetic MGs under applied bending stress. We show that the irreversible domain wall movement region and the irreversible domain wall rotation region in the M-H curve represent the stress relief, which can be well reflected by the demagnified magnetic anisotropy. The magnetic coercivity and effective permeability variations in the lower frequency regime also represent the stress relief state. These observations have implications for understanding the relationship between the stress relief, microstructure change, and magnetic softness in magnetic MGs and might be helpful for the performance improvement of the ferromagnetic glassy materials.