Relaxor Ferroelectric Crystals Research Articles

Enhanced electric property of relaxor ferroelectric crystals with low AC voltage high-temperature poling

We demonstrated high free dielectric permittivity (ε 33 T/ε 0) > 8000 and piezoelectric coefficient d 33 > 1950 pC/N of 72Pb(Mg1/3Nb2/3)O3-28PbTiO3 (PMN–28PT) single crystals (SCs) obtained by low-voltage AC poling (LV ACP) of 1.5 to 3.5 kVRMS cm−1 at a high temperature (HT) of 80 °C in an air atmosphere. The minimum standard deviation (σ) of 170 was similar to conventional DC poling (DCP) and a high average ε 33 T/ε 0 of 8800 was confirmed with a 2.0 kV RMS cm−1 of ACP for five samples. The ACP voltages were less than 50% compared with previous studies of 2.9 to 8.5 kV RMS cm−1. We assume ACP at 80 °C with a frequency of 0.1 Hz decreased coercive field E C the most which led to easy poling reversal. The LVHT air ACP process is very effective in obtaining enhanced dielectric and piezoelectric properties for PMN–PT SC transducers for medical echo ultrasound equipment application with less risk of breakdown and organic solvent-free for poling.

Application study of Mn-doped PIN-PMN-PT relaxor ferroelectric crystal grown by Vertical Gradient Freeze method

A 3-inch Mn:PIN-36%PMN-32%PT (Generation III) relaxor ferroelectric crystal was grown using the Vertical Gradient Freeze method. Crystals of [1, 11] and [111] orientations were prepared and studied, evaluating their dielectric constants, piezoelectric coefficients, electromechanical coupling coefficients, loss tangents and pyroelectric coefficients. It is shown that in pyroelectric applications, [111]-poled crystals are particularly suitable for high performance sensors due to a relatively high pyroelectric coefficient, low loss tangent. In addition, the specific heat is lower as compared to LiTaO3. It is also shown that the alternating current (AC) poling has a more significant effect on the [001]-poled crystal than on the [011]- and [111]-poled crystals due to the lattice distortion induced by a strong electric field along the [001] direction.

5″ diameter PIN-PMN-PT crystal growth by the Bridgman method

Pb([Formula: see text][Formula: see text])O3-Pb([Formula: see text][Formula: see text]O3-PbTiO3 (PIN-PMN-PT) relaxor ferroelectric crystals in 5″ diameter by 5″ length were grown by the Bridgman (BR) method for the first time. Typical issues in the crystal growth concerning large volume of the melt, high density of the crystal and corrosion of the melt on the wall of Pt crucible are discussed.

Enhanced electro-optic beam deflection of relaxor ferroelectric KTN crystals by electric-field-induced high permittivity: publisher's note.

This publisher's note contains corrections to Opt. Lett.44, 5557 (2019)OPLEDP0146-959210.1364/OL.44.005557.

Enhanced electro-optic beam deflection of relaxor ferroelectric KTN crystals by electric-field-induced high permittivity.

Most applications of a ferroelectric-based electro-optic (EO) beam deflector have been limited by the high applied voltage. In this Letter, we report a dramatically increased EO beam deflection in relaxor ferroelectric potassium tantalate niobate (KTN) crystals by using the electric-field-enhanced permittivity. Due to the existence of the electric-field-induced phase transition in relaxor ferroelectric materials, the dielectric permittivity can be substantially increased by the applied electric field at a certain temperature. Both the theoretical study and the experimental verifications on the enhanced beam deflection and EO effect in the case with the electric-field-induced high permittivity were conducted. The experimental results confirmed that there was a three-fold increase in the deflection angle, which represented a dramatic increase in the deflection angle. By offering a wider deflection range and a lower driving voltage, such a largely enhanced beam deflection is of great benefit to the KTN deflector.

Study of thermal and spatial dependent electric field-induced phase transition in relaxor ferroelectric crystals using Raman spectroscopy

Electric field-induced phase transition in perovskite relaxor ferroelectric crystals has been studied using Raman spectroscopy. The findings revealed that by switching the applied electric field, the intensity ratio of the Raman spectra of the electric field-induced phase transition in relaxor ferroelectric potassium tantalate niobate KTa0.61Nb0.39O3 (KTN) crystals can be a function of temperature and thermal history, which is explained by the two-stage kinetic model of first-order phase transition in disordered ferroelectrics. Moreover, because of the charge injection by the applied voltage, the non-uniform electric field-induced phase transition in KTN was spatially resolved by Raman mapping. The results of this study will be of use for fundamental scientific studies on the physical mechanisms of the electric field-induced phase transition in perovskite relaxor ferroelectric materials and has practical applications for electromechanical and electro-optic devices and systems.

Dielectric Relaxor and Conductivity Mechanism in Fe-Substituted PMN-32PT Ferroelectric Crystal

Fe-substituted PMN-32PT relaxor ferroelectric crystals were grown by a high-temperature flux method. The effects of charged defects on the dielectric relaxor and conductivity mechanism were discussed in detail. The Fe-substituted PMN-32PT crystal showed a high coercive field (Ec = 765 V/mm), due to domain wall-pinning, induced by charged defect dipoles. Three dielectric anomaly peaks were observed, and the two dielectric relaxation peaks at low temperature were associated with the diffusion phase transition, while the high temperature one resulted from the short-range hopping of oxygen vacancies. At temperature T ≤ 150 °C, the dominating conduction carriers were electrons coming from the first ionization of oxygen vacancies. For the temperature range from 200 to 500 °C, the conductivity was composed of the bulk and interface between sample and electrode, and the oxygen vacancies were suggested to be the conduction mechanism. Above 550 °C, the trapped electrons from the Ti3+ center were excited and played a major role in electrical conduction. Our results are helpful for better understanding the relationship between dielectric relaxation and the conduction mechanism.

Origin of Improvement in Mechanical Quality Factor in Acceptor-Doped Relaxor-Based Ferroelectric Single Crystals

Ferroelectric materials with high mechanical quality factors ${Q}_{m}$ are used in high-power electromechanical devices, but the physical mechanism of ${Q}_{m}$ enhancement is not well understood. This study uses Rayleigh analysis to quantitatively investigate the pinning effect in acceptor-doped relaxor ferroelectric crystals. Enhancement of the longitudinal factor ${Q}_{33}$ is attributed to restricted polarization rotation, while that of the shear factor ${Q}_{15}$ is ascribed to both polarization rotation and clamped domain-wall motion. This insight into the underlying physics will guide the material optimization of device performance in $e.g.$ transducers and sensors.

Complete stress-induced depolarization of relaxor ferroelectric crystals without transition through a non-polar phase

The development of relaxor ferroelectric single crystal technology is driven by the ability to tailor ferroelectric properties through domain engineering not achievable in polycrystalline materials. In this study, three types of domain-engineered rhombohedral Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals were subjected to transverse high strain rate loading. The experimental results indicate that the domain configuration has a significant effect on the stress-induced depolarization and the associated charge released. A complete depolarization of the single-domain crystals with 3m symmetry is observed, while multidomain crystals with 4mm and mm2 symmetries retain a fraction of their initial remanent polarization. The complete depolarization of single-domain crystals is unique without transition to a non-polar phase, with a stress-induced charge density of 0.48 C/m2. This is up to three times higher than that of the multidomain crystals and PbZrxTi1−xO3 ferroelectric ceramics that are critical for ultrahigh-power transducer applications. The main offering of this work is to propose a detailed mechanism for complete stress-induced depolarization in ferroelectric crystals which does not involve an intermediate transformation to a non-polar phase.

Optical properties induced and ferroelectric properties enhanced of the PMN-32PT:Ho relaxor ferroelectric crystals

Relaxor ferroelectric crystals PMN-32PT:Ho were prepared by using the flux method. Phase structure and surface morphology of the crystals were performed by using the X-ray diffraction analysis (XRD) and scanning electron microscope (SEM), respectively. A broad dielectric peak in temperature dependent of dielectric spectrum was observed during the phase transition of the PMN-32PT:Ho crystals. The modified Curie-Weiss and Lorentz-type laws were used to describe the dielectric relaxor behavior of the crystals. Optical performances were characterized by using the fluorescence spectrophotometer, Fourier transform infrared spectroscopy (FTIR) and ultraviolet spectrophotometer. Effects of Ho3+ modification on structure, dielectric relaxation, ferroelectric and optical properties of the PMN-32PT crystals were investigated. Ferroelectric properties were improved and the larger coercive field EC was found to be 4.31 kV/cm at room temperature by the Ho modification. Optical performances of the PMN-PT crystals could be induced by the introduction of the Ho ions. The green light of 550 nm and red light of 630 nm were emitted under the excitation at 465 nm. The mechanism of the up-conversion luminescence for as-grown crystals was also discussed.

In Situ Di-, Piezo-, Ferroelectric Properties and Domain Configurations of Pb(Sc1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 Ferroelectric Crystals

Relaxor ferroelectric crystals, such as Pb(Mg1/3Nb2/3)O3–PbTiO3 and Pb(Zn1/3Nb2/3)O3–PbTiO3, exhibit high piezoelectric properties. However, they cannot meet the need of high power transducers, due to their low phase transition temperatures and low coercive fields. Thus, it is urgent to develop new-type ferroelectric crystals. Here, a ternary solid solution of Pb(Sc1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 is a good candidate. By the regulation of growth techniques and the control of raw compositions, Pb(Sc1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals with different compositions are obtained, which present perovskite phases without any trace of impurity. In situ investigations of di-, piezo-, ferroelectric properties and the observation of domain configurations are realized in Pb(Sc1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals, which exhibit large di-, ferro-, piezoelectric responses, typical domain switching, high poled and thermal stabilities. At room temperature, the maximum piezoelectric constant is found to ...

Strong anisotropy of electric field effects on uniaxial relaxor ferroelectric Sr0.75Ba0.25Nb2O6 crystals proved by acoustic emission

[001] oriented Sr0.75Ba0.25Nb2O6 uniaxial relaxor ferroelectric crystals have been studied by acoustic emission in the temperature range of 20÷200 °C and under an external electric field up to 1 kV/cm. Under the application of an electric field the temperature of a dielectric maximum exhibits a nontrivial behavior: it remains constant at first, secondly steep decreases down to some threshold field, and thirdly starts to increase as a field enhances, whereas the same temperature of a dielectric maximum under a bias electric field to [100] oriented Sr0.75Ba0.25Nb2O6 crystals exhibits a smoothed minimum before the start to increase as a field enhances (E. Dul'kin et al., J. Appl. Phys. 110, 044106 (2011)). Such a difference of electric field effects in c- and a-cut crystals is discussed from the viewpoint of random-bond-random-field model of relaxor ferroelectrics. By the comparison between experimental and theoretical data, a dipole moment of the PNR was estimated to be 0.1 (C cm).

Lattice-Rotation Vortex at the Charged Monoclinic Domain Boundary in a Relaxor Ferroelectric Crystal.

We present evidence of lattice-rotation vortices having an average radius of ∼7 nm at the ferroelectric domain boundary of (1-x)Pb(Zn_{1/3}Nb_{2/3})O_{3}-xPbTiO_{3} (x=0.08). Maps of crystal orientations and domain symmetry breaking are obtained using scanning convergent beam electron diffraction, which show fractional rotation vortices near the 50° monoclinic domain walls. The merging of 2D and 1D topological defects is consistent with inhomogeneous boundary charge and expected to have a large impact on the domain-switching mechanisms in relaxor ferroelectric crystals and ferroelectric devices.

The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals.

The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

X-ray powder diffraction methods for the determination of composition and structural parameters of Cr- and Ni-doped Sr0.61Ba0.39Nb2O6 crystals

The possibility of using the Rietveld method for refinement of main structural parameters of both nominally pure (SBN-1) and Cr- (SBN-2: Cr2O3, 0.01wt.%) and Ni- doped (SBN-3 and SBN-4: Ni2O3, 0.05wt.% and 1.0wt.%, respectively) ground relaxor-ferroelectric crystals of initial composition Sr0.61Ba0.39Nb2O6, grown by the modified Stepanov technique, has been shown. It was established that the general composition of the crystals can be described as Sr∼0.55Ba∼0.39Nb2O6−δ with possible vacancies in the oxygen sites; the composition of SBN-4 crystal differs from other samples by another distribution of Sr ions over the crystallographic sites of the structure. The correlation between the thermal parameters of oxygen atoms and the disorder on their sites as well as the Ni content in SBN-3 and SBN-4 crystals has been found. The relationship between the unit cell parameters of undoped and Cr- and Ni-doped Sr0.61Ba0.39Nb2O6 crystals and Sr and Ba content, and second-order nonlinear susceptibility values, χ(2), has been revealed.

Structure and properties of Pb(Lu1/2Nb1/2)O3–0.2PbTiO3 relaxor ferroelectric crystal

Ferroelectric crystal Pb(Lu1/2Nb1/2)O3–0.2PbTiO3 (PLN–0.2PT) was successfully obtained by a top-seed solution growth technique. At room temperature the symmetry was orthorhomic according to X-ray diffraction (XRD). The super-lattice reflections were identified by XRD and transmission electron microscope (TEM). The micro-domain structure was detected by TEM. The temperature dependence of the dielectric constant (ϵ′) shows a typical relaxor behavior. The temperature dependence of coercive electric field and remnant polarizations were investigated, which also shows the relaxor feature.

Detection of the critical end point in PbSc0.5Ta0.36Nb0.14O3 relaxor ferroelectrics crystals via acoustic emission

PbSc0.5Ta0.36Nb0.14O3 relaxor-ferroelectric crystals were studied by the means of dielectric and acoustic emission (AE) methods in the temperature range of 180–300 K. In zero dc electric field (E) no AE was detected at the smeared dielectric maximum Tm ≈ 260 K characteristic for canonical relaxor ferroelectrics. Under the E a phase transition appears at TC = 217 K for E ∼ 1 kV cm−1. The TC(E) dependence is linear with an anomaly point at E ∼ 1.3 kV cm−1, at which dTC/dE abruptly changes. At this E value the AE rate exhibits a maximum. The anomalous E point is assigned to be the critical end point for this solid solution.

Electrostrictive effect in Pb(Mg1/3Nb2/3)O3-xPbTiO3 crystals

The electrostrictive effect was investigated in Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) relaxor ferroelectric crystal, a representative high performance piezoelectric material, with respect to orientation, temperature, and composition. The electrostrictive coefficients Q11C, Q12C, and Q44C of PMN-xPT (x = 0.25−0.37) crystals were found to be on the order of 0.055, −0.024, and 0.020 m4/C2, respectively. The maximum and minimum Q33* were found to be along 〈100〉 and 〈111〉 directions, being about 0.055 and 0.014 m4/C2, respectively, showing a strong anisotropic behavior, which is inherently associated with the oxygen-octahedra structure. In contrast to piezoelectric and dielectric responses, the electrostrictive coefficients Q are found to be insensitive to the ferroelectric phase transition, no matter it is induced by the temperature or composition.

Stress dependence of thermally driven pyroelectric charge release during FER-FEO phase transformations in [011] cut relaxor ferroelectric crystals

The stress dependence of thermally driven polarization change is reported for a ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation in [011] cut and poled Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT). A jump in polarization and strain is associated with a phase transformation of the ferroelectric material. The phase transformation temperature can be tuned, over a broad temperature range, through the application of bias stress. This phenomenon has applications in the field of energy harvesting and thermal sensing.

Elastic softening and polarization memory in PZN-PT relaxor ferroelectrics

Substantial elastic softening in the cubic phase of PZN-PT relaxor ferroelectric crystals is observed as a large hysteresis between the RUS frequencies from poled and depoled crystals. This is due to static switchable polar nanoregions (PNR) at $T$*, well below the conventional Burns temperature but \ensuremath{\sim}50 K above the ferroelectric transition. Elastic softening due to polarization of the PNR shows polarization memory through two phase transitions and is greater than the softening associated with polarization of the ferroelectric phases. This emphasizes that PNR dominate the material properties at all temperatures below $T$*.