DC Poling Research Articles

Advancing piezoelectric properties of barium titanate ceramic through AC + DC field poling over Curie temperature

The significance of increased domain nucleation sites from smaller grain size (GS) of barium titanate (BT) ceramics on piezoelectric properties was analyzed for different types of poling, including conventional DC poling, modified DC poling, and AC plus DC poling, conducted at different poling temperatures. The AC plus DC poling conducted at 1.5 °C above the Curie temperature (T C) showed the highest piezoelectric constant (d 33) of 528 pC/N, with an average domain size of 100 nm observed after poling. The d 33 improvement was attributed to smaller domain size formation from field-induced phase transitions and homogenous distribution of point defects achieved by the AC field. Comparative analysis with larger grain BT ceramics under AC plus DC poling suggests that defects and volume fraction of grain boundaries in BT ceramics could have an effect on domain sizes.

Enhanced piezoelectrical properties of Pb(Zn1/3Nb2/3)O3 - PbTiO3 single crystals by AC poling

We investigated the effectiveness of AC poling (ACP) processes for [001] direction oriented Pb(Zn1/3Nb2/3)O3-0.055PbTiO3 (PZN-PT) single crystals (SCs) and obtained a dielectric constant ε 33 T/ε 0 of 6680 and piezoelectric strain constant d 33 of 2760 pC/N, a piezoelectric charge constant g 33 of 46.7 × 10−3 Vm/N, and a figure of merit (FOM) (d 33 × g 33) of 129 × 10−12 m2/N. These values were 19%, 31%, 10%, and 45% higher than those of DC poling PZN-PT SC, respectively. The phase change temperature T pc, Curie temperature T c, and acoustic impedance (Z 33) of the ACP PZN-PT SC were 121 °C, 165 °C, and 30.5 MRayls, respectively. Compared with Pb(Mg1/3Nb2/3)O3−0.3PbTiO3 SCs, the higher T pc, T c, and FOM and lower Z 33 of the PZN-PT SCs enable the applications in high temperature with superior Z 33 matching to water and human body than conventional Pb(Mg1/3Nb2/3)O3−0.3PbTiO3 SCs , and these findings are vital for a wide range of ultrasonic transducer applications.

Effects of quenching on domain switching and electric field-induced phase transformations in Na0.5Bi0.5TiO3-NaNbO3 ceramics

Quenching from high temperatures has been identified as a useful means to enhance the piezoelectric properties and thermal stability of bismuth-based perovskite ferroelectrics. In the present work, it is demonstrated that quenching leads to improvement of depolarization temperature, ferroelectric and piezoelectric properties in Na0.5Bi0.5TiO3-NaNbO3 (NBT-0.1NN) ceramics. In-situ synchrotron x-ray diffraction measurements indicated an irreversible transformation from cubic to coexisting cubic and rhombohedral phases during the application of a high electric field, for both as-sintered and quenched ceramics. These results confirm the non-ergodic relaxor ferroelectric nature of the materials. DC poling induced a transformation to single-phase rhombohedral structure in both cases, with highly textured domain configurations. These well-oriented ferroelectric domain states were relatively stable under subsequent bipolar electric field cycling. For the pre-poled NBT-0.1NN ceramics, the quenched samples were found to exhibit the highest intrinsic (lattice strain) and extrinsic (domain switching) contributions to electrostrain, due to the increased rhombohedral distortion.

Optimization of conditions for AC plus DC poling above Curie temperature of barium titanate ceramic for piezoelectric property enhancement

Optimization of conditions for AC plus DC poling above Curie temperature of barium titanate ceramic for piezoelectric property enhancement

Reply to comment on “Ferroelectric composite-based piezoelectric energy harvester for self-powered detection of obstructive sleep” by A. Tkach and O. Okhay

In this contribution, we reply to comments made by Tkach et al. in our publication J. Materiomics 2023; 9:609. The main interest of our work is to synthesize a lead-free material, SrTi2O5 (STO), and then utilize it in the formation of composites and finally design the piezoelectric nanogenerator (PENG) for self-powered sensor applications. The authors have observed the presence of piezoelectric voltage and current output from the PENG. The authors humbly indicate that the PENG devices were poled using a DC poling setup as conditions mentioned in J. Materiomics 2023; 9:609 (Panda et al., 2023) [1]. The doping of STO into the PDMS increased from 2% to 20% (in mass). In this process, the piezoelectric output of the PENG device was observed to be highest for 15% (in mass) STO-PDMS composite. Besides, we agree with the comment raised by Tkach et al., and further we have addressed the issues in a step-by-step response as follows.

Castor‐oil derived polyurethane/barium titanate piezoelectric smart composite coatings for energy harvesting applications: Prediction and experimental characterization of electro‐elastic properties

AbstractSustainable and environment‐friendly polymer composite smart paints/coatings with polyurethane (PU) derived from castor‐oil (CO) as the matrix and barium titanate (BTO) microparticles as piezo‐active inclusions (2, 4, 6, 8, and 10 vol.%) have been prepared employing ultrasonication and solvent casting, followed by contact DC poling method. Relative dielectric constants varied from 5.26 ± 0.37 for pristine COPU to 8.9 ± 0.36 for COPU/10 vol.% BTO composite, at a frequency of 1 kHz. Piezoelectric strain constant d33 of the poled films varied from 0.0 pC/N for pristine castor‐oil based polyurethane (COPU) to 1.2 pC/N for COPU/10 vol.% BTO (CPBT‐5) composite. Tensile tests showed that the elastic modulus varied from 1.98 ± 0.003 MPa for pristine COPU to 5.13 ± 0.02 MPa for COPU/10 vol.% BTO composite. Dynamic mechanical analysis confirmed the viscoelastic nature of the smart paints. Measurement of current–voltage response under different compressive loads indicates that COPU/10 vol.% BTO composite can generate a current of ~28 nA and voltage of ~8 V under a dynamic compressive load of 40 N, applied at a frequency of 1 Hz. These experiments were complemented by Fourier transform infra‐red spectroscopy and scanning electron microscopy. In addition, finite element analyses based on periodic boundary conditions have been performed to predict the effective electro‐elastic properties of these piezoelectric smart composite coatings.Highlights Castor‐oil‐based PU piezoelectric composites with BTO inclusions were developed. Increase in BTO content up to 10 vol.% increases dielectric constant by ~1.7 times. COPU/BTO composites exhibit significantly increased piezoelectric response. Elastic and viscoelastic properties are also enhanced with increasing BTO content. Finite element models show a good match with experimental results.

Self-poling and DC poling of Mn doped Pb(Mg1/3Nb2/3)O3-Pb(ZrTi)O3 single crystals grown by a solid state crystal growth process

Acceptor Mn-doped Pb(Mg1/3Nb2/3)O3-Pb(ZrTi)O3 (PMN-PZT) single crystals (SCs) grown by a solid state crystal growth (SSCG) process electrode with Ag at 650 °C showed a high piezoelectric coefficient (d 33) of 520 pC N−1 at 25 °C by self-poling, i.e. without any additional poling process. Upon heating above the Curie temperature (T c), the impedance characteristics’ oscillation peak due to piezoelectricity disappears. However, as the temperature falls below T c, these oscillation peaks reemerge around T c. And when the temperature is further lowered to around RT, the impedance characteristics return to almost the original state. The d 33 values of the non-poled SCs, initially 520 pC N−1, increased to 910 pC N−1 after DC poling (DCP) and to 1170 pC N−1 after field cooling (FC)-DCP. These values surpass those of commercially available high-Qm PZT ceramics. These high-Qm PMN-PZT single crystals developed using the SSCG method demonstrate huge potential for future transducer applications.

Comparison of field-cooling DC poling and AC poling for lead perovskite relaxor-PbTiO3 single crystals grown by a continuous feeding Bridgman process

We investigated the effectiveness of poling processes for Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals (SCs) produced using a continuous feeding Bridgman method, which is known to produce a high property uniformity. The four studied poling processes are: (I) standard direct current poling (STD-DCP); (II) low-voltage field-cooling DCP (LV-FCP); (III) high-voltage field-cooling DCP (HV-FCP); and (IV) mid-temperature alternating current poling (MT-ACP). The highest free dielectric constant (ε 33 T/ε 0) and piezoelectric constant (d 33) were obtained by MT-ACP (ε 33 T/ε 0 = 11 000, d 33 = 3000 pC/N), followed by LV-FCP (ε 33 T/ε 0 = 7500, d 33 = 2400 pC/N), HV-FCP (ε 33 T/ε 0 = 6250, d 33 = 1850 pC/N), and STD-DCP (ε 33 T/ε 0 = 6200, d 33 = 1800 pC/N). The LV-FCP SC showed a 21% and 33% increase in ε 33 T/ε 0 and d 33 compared to that of the STD-DCP SC; however, this was not as much as the 77% and 67% improvement of the MT-ACP SC. These results provide guidance for SC transducers.

On 3D printing of electro-active PVDF-Graphene and Mn-doped ZnO nanoparticle-based composite as a self-healing repair solution for heritage structures

Construction is the part of human activity which is directly linked to urbanization for moving ahead on the path of growth and prosperity. Construction activities in past centuries are now part of our precious heritage. The repair and maintenance of heritage structures are of great importance for present-day researchers. One of the most common damage these century-long constructions faces are in form of surface cracks. In the present study, investigations were performed for a 3D printing-based customized solution for crack repair and maintenance of heritage structures. In this study, polyvinylidene fluoride (PVDF) polymer was reinforced with graphene (Gr) and Mn-doped ZnO nano-particles to prepare a smart composite material for crack repair and restoration. The composite was successfully 3D printed on fused deposition modeling (FDM) based 3D printer after investigating its rheological, thermal, and mechanical properties. The in-house developed composite was tested for smart characteristics to use as a programmable solution for filling cracks. The piezoelectric property and dielectric constant of 3D printed disk-shaped composite (PVDF-Gr-Mn-ZnO) were obtained after DC poling (to be used as stimulus) of the functional prototype. The results of the study suggest that the electro-active nature, volumetric change, and charge storing capacity of the additively manufactured composite may be used practically to acquire the shape of cavity/crack present in the constructed wall and repair the damages that occurred in a heritage site. The photoluminescence (PLS) and atomic force microscopy (AFM) analysis was used to ascertain the properties of the prepared composite. Also, the results obtained from the morphological analysis are reported to support the outcomes of the research.

Grain Size Effects in Mn-Modified 0.67BiFeO3-0.33BaTiO3 Ceramics.

Grain size can have significant effects on the properties of electroceramics for dielectric, piezoelectric, and ferroelectric applications. Here, we systematically investigate the effect of grain size on the structure and properties of Mn-modified 0.67BiFeO3-0.33BaTiO3 ceramics, an important lead-free piezoelectric ceramic that exhibits both a high piezoelectric coefficient and a high Curie point. Ceramics with average grain sizes ranging from 0.46 to 6.85 μm were prepared using conventional and spark plasma sintering. It was found that the morphotropic phase boundary compositions are composed of two polar structures, rhombohedral and tetragonal, with DC poling inducing an increase in the fraction of the rhombohedral phase. All ceramics show relaxor behavior and their freezing temperature moves to higher temperatures with increasing grain size, although their Burns temperature is independent of grain size. In fine-grained ceramics, which show pronounced relaxor behavior, significant grain size dependency is seen in dielectric, piezoelectric, and ferroelectric properties, which is attributed to the presence of single ferroelectric domains and high concentrations of polar nanoregions. In coarse-grained ceramics, a critical grain size of 2.83 μm yields the highest dielectric permittivity at room temperature, with the piezoelectric coefficient plateauing at this grain size, which can be attributed to the contribution of both polar nanoregions and high domain wall density.

Dielectric, piezoelectric, and spurious mode vibration properties by four types of waveforms AC poling for Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

Four types of waveforms of AC poling (ACP) and DC poling (DCP) were applied on [001]-oriented 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-28PT) ferroelectric single crystals (SCs) at 80 °C. High voltage (5 kV cm−1) ACP of all four waveforms and DCP SCs tend to show low piezoelectric coefficient (d 33) less than 1660 pC/N and large spurious-mode vibration (SMV) at the thickness mode vibration (TMV) on impedance spectrum. The highest d 33 of 1830 pC/N was obtained by a triangle wave of 3 kV cm−1 SCs with tiny SMV. By contrast, low voltage (1.5 kV cm−1) ACP SCs with sine and triangle waveforms showed high d 33 of 1750 pC/N and 1670 pC/N without any SMV. We consider that the SMV is more easily caused by the over-poling of PMN-28PT SC. This information will help realize high piezoelectric properties and high production yield for ACP PMN-PT SC transducers for high-resolution medical ultrasound imaging equipment.

Photoactive electrically switchable van der Waals semiconductor NbOI2

Room temperature van der Waals ferroelectric materials whose ferroelectricity may survive down to atomic layer limit are highly desirable for device miniaturization. In this article, we present the optically active reconfigurable room temperature rectification in a recently predicted ferroelectric van der Waals material NbOI2. NbOI2 devices with a thin (∼17-unit cells) single crystalline channel and inert graphite electrodes were assembled into two-terminal devices which showed >100 × photoresponse to 405 nm laser. By DC poling on a 1-μm-channel NbOI2 device, the photocurrent changed from symmetric to single-Schottky-diode type. The polarity of such rectification can be switched back and forth by DC poling along opposite directions. Such reconfigurability evidences the existence of in-plane room temperature ferroelectricity in thin NbOI2 and its potential in nonvolatile optoneuromorphic computing and nonvolatile technologies.

Effects of poling on the electrical and electromechanical response of PMN–PT relaxor ferroelectric ceramics

The dielectric and piezoelectric response of the Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT) polycrystalline ceramics after different poling procedures is examined and explained with respect to the phase composition and the domain structure. In the monoclinic (M) compositions a twice lower AC poling field is needed for a similar piezoelectric coefficient (d33) relative to DC poling. The high efficiency of AC poling of the M phase is assigned to its unique structure with low-angle nanodomain walls that are highly responsive to external fields and move in a ‘cascade-like’ motion, contributing to strains up to 0.5%. While the highest d33 is achieved at the morphotropic phase boundary (MPB), the dielectric permittivity of all room-temperature poled samples reached its peak on the tetragonal side of the MPB. The latter is assigned to the broadening of the MPB when poling above the inclined MPB, which can thus be manipulated by the proper poling conditions.

Poling effect on the electrostrictive and piezoelectric response in CH3NH3PbI3 single crystals

Methylammonium lead triiodide perovskites (MAPbI3) have demonstrated a large electrostrictive strain up to 1%, which was theoretically proved to be related to the additional defects under applied bias voltages. However, as this effect was detected only at a low frequency, we explored the electrostrictive response at a higher frequency (4 kHz) by using ac poling at 1 Hz. In such conditions, the electrostrictive coefficient was evaluated at –45.7 nm2 V−2, i.e., quite larger than the results under dc poling or in unpoled samples. The occurrence of a high-frequency electrostrictive effect may be correlated with the defects that rise in the ac poled samples from the ion migration under reverse bias as it was also demonstrated from the shift of the dielectric loss peak in the considered systems. In parallel to the electrostrictive effect, the piezoelectric response shows a drastic increase after the ac and dc poling due to the lattice distortion induced by the applied electric field. Based on the above approach, the achieved electrostrictive and piezoelectric responses at 4 kHz in MAPbI3 may open opportunities in the area of actuators, energy-harvesting, and micro-electromechanical systems.

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.

Space Charge Accumulation and Decay in Dielectric Materials with Dual Discrete Traps

Charge trapping and de-trapping properties can affect space charge accumulation and electric field distortion behavior in polymers. Dielectric materials may contain different types of traps with different energy distributions, and it is of interest to investigate the charge trapping/de-trapping dynamic processes in dielectric materials containing multiple discrete trap centers. In the present work, we analyze the charge trapping/de-trapping dynamics in materials with two discrete traps in two cases where charges are injected continuously or only for a very short period. The time dependent trapped charge densities are obtained by the integration of parts in the case of continuous charge injection. In the case of instantaneous charge injection, we simplify the charge trapping/de-trapping equations and obtain the analytical solutions of trapped charge densities, quasi-free charge density, and effective carrier mobility. The analytical solutions are in good agreement with the numerical results. Then, the space charge dynamics in dielectric materials with two discrete trapping centers are studied by the bipolar charge transport (BCT) model, consisting of charge injection, charge migration, charge trapping, de-trapping, and recombination processes. The BCT outputs show the time evolution of spatial distributions of space charge densities. Moreover, we also achieve the charge densities at the same position in the sample as a function of time by the BCT model. It is found that the DC poling duration can affect the energy distribution of accumulated space charges. In addition, it is found that the coupling dynamic processes will establish a dynamic equilibrium rather than a thermodynamic equilibrium in the dielectric materials.

Polarization investigation of Mn-doped 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystals for infrared detecting application

This work has been carried out to investigate the poling temperature and poling field dependences of pyroelectric and dielectric properties of ⟨111⟩ oriented Mn-doped 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystals. Poling treatments are implemented at 25 °C, 90 °C, and 120 °C with DC poling electric fields of 1, 2, 3, and 4 times the corresponding coercive field, respectively. The correlation between ferroelectric domain transition and pyroelectric properties is investigated. The optimized pyroelectric and dielectric performances with the highest pyroelectric coefficient p and the lowest dielectric loss tan δ, as well as the optimized figures of merit, are achieved by poling samples at 90 °C in this study, instead of those conventionally poled at nearly Curie temperature (120 °C). Moreover, excellent long-term performances of 90 °C poled Mn-PMN-0.28PT crystals are disclosed over a 30-day range.

Polarization imprint effects on the photovoltaic effect in Pb(Zr,Ti)O3 thin films

The polarization imprint along with the photovoltaic (PV) effect has been studied in Pt/Pb(Zr0.3Ti0.7)O3/SrRuO3 ferroelectric capacitors. It is shown that the positive DC poling induces the imprint with a downward direction whereas the negative DC poling suppresses the imprint (i.e., rejuvenation). In the polarization up state, the imprinted capacitor exhibits degraded PV properties compared with the rejuvenated one. This may be because the imprint reduces the number of upward domains, thus lowering the driving force for the PV effect. In the polarization down state, however, the rejuvenated capacitor enters the imprinted state spontaneously. This rejuvenation-to-imprint transition can be further aggravated by applying positive voltages and ultraviolet illumination. It is proposed that the domain pinning/depinning, which are associated with the oxygen vacancies and trapped electrons modulated by polarization, voltage, and illumination, may be responsible for the polarization imprint and rejuvenation. Our study therefore sheds light on the correlation between the polarization imprint and the PV effect in the ferroelectrics and also provides some viable suggestions to address the imprint-induced degradation of PV performance.

AC impedance of poled glass during de-poling

It has been observed in the literature that when the DC poling voltage is removed at the end of the poling process in glass in a so called de-poling experiment, the small signal AC impedance as measured by impedance spectroscopy increases immediately. It is shown that this effect can be explained if the DC voltage causes nonlinear ionic conduction to occur in the poled layer. The DC field changes the barrier height over which ions have to jump from one site to another and this also effects the AC resistance; by removing the DC field the original barrier height is restored thus increasing the AC resistance. Analysis of experimental data using poled soda-lime glass supports this interpretation.

Polarization rotation in copper doped zinc oxide (ZnO:Cu) thin films studied by Piezoresponse Force Microscopy (PFM) techniques

In this study, the polarization rotation with approximately 180⁰, i.e., the phenomenon that polarization changes its angle by ∼180°, in copper doped ZnO (ZnO:Cu) films under an applied electrical field are characterized by using Piezoresponse Force Microscopy (PFM) based techniques. First, the Band Excitation PFM (BE-PFM) measurements show that the polarizations in ZnO:Cu sample prefer the upward direction when the copper concentration is higher (above 8 at.%). Second, it is found that the piezoresponse property is enhanced with increasing the copper concentration. Third, by conducting PFM in spectroscopy mode (PFS), it reveals that the anomalous hysteresis loops occurs at certain locations and can be tuned to symmetry by increasing the bias window. Furthermore, it is found the built-in field during the DC poling processes are contributed by the oxygen vacancy in the films. The PFS results from as-grown sample and samples annealed in air and vacuum also verify that the oxygen vacancy plays an important role in the polarization rotation. Finally, by using the switching spectroscopy PFM (SS-PFM) technique, it is confirmed that the local polarization rotation is mediated by copper concentration. The parameters determined from the PFS measurements, including positive and negative coercive bias, Vp and Vn, coercive bias, Ec, maximum and remanent switchable responses, Rs and R0, all increase with the copper concentration.