Low Poling Field Research Articles

Poling procedures and piezoelectric response of (Ba0.85Ca0.15Zr0.1T0.9)O3 ceramics

ABSTRACT The goal of the current report was to find the optimal poling conditions: poling field, poling time and poling temperature for lead-free (Ba0.85Ca0.15Zr0.1T0.9)O3 ceramic. It has been noticed that the low poling field (< 2 kV/mm) was insufficient for obtaining ideal poling state (θ = 90°) due to the incomplete switching of domains and thus low piezoelectric properties (d33 ≤ 438 pC/N and kp ≤ 49%). However, relevance of higher poling voltage (> 2 kV/mm) may induce electric breakdown and physical defects such as cracks in the sample, which also leads degradation of piezoelectric properties. The optimal poling field, poling time and poling temperature was found to be 2 kV/mm, 10 min and 24°C, i.e., near room temperature, respectively to achieve nearly ideal poling state (θ = 86°) obtained by impedance spectra, and thus enhanced piezoelectric constant d33 = 505 pC/N and kp = 56% at room temperature. The O-T phase transition point was identified at 32.6°C, for which a peak value of d33(E=0V) = 622 pm/V was realized.

Low driving field-induced large strain in MnO2-modified 0.76Bi1/2Na1/2TiO3-0.24SrTiO3 lead-free piezoceramics

MnO2-modified 0.76Bi1/2Na1/2TiO3-0.24SrTiO3 (BNT-24ST) lead-free piezoceramics were synthesized by a conventional solid-state method. The introduction of MnO2 influences the phase structure and increases the grain size. Increasing the MnO2 content shifts the ferroelectric-relaxor transition temperature to below room temperature. This leads to a transition from ferroelectric behavior to ergodic-relaxor behavior. A large electrostrain of 0.18% and a normalized strain (Smax/Emax) of 902 pm/V with an ultra-low driving field of 2 kV/mm are achieved for the 0.25 wt% MnO2 doped BNT-24ST. A temperature-insensitive Smax/Emax of above 610 pm/V from room temperature to 90 °C is achieved at 4 kV/mm. This is attributed to the modification by MnO2 and the low poling field. Excellent mechanical performance of Young’s modulus E~127.4 GPa and fracture toughness KIC~1.38 MPa.m1/2 are also obtained, which are better than those reported for PZT-based ceramics. The results indicate the BNT-24ST with MnO2 ceramic is a promising candidate for piezoactuator applications.

Microstructure and electrical properties of 0-3 connectivity barium titanate−Portland cement composite with 40% barium titanate content

ABSTRACTIn this paper, a study is presented on the microstructure, dielectric and piezoelectric properties of 0–3 connectivity barium titanate-Portland cement composite with 40% barium titanate content at this composition has an acoustic impedance that match with concrete structure. The results show that both of dielectric constant (ϵr) and dielectric loss (tanδ) of composite were found to decrease with increasing frequency. The ϵr value of composite was 239 at a frequency of 1 kHz. In addition, the ferroelectric hysteresis loops of composite indicate that the “apparent” remnant polarization increases as an applied external electrical field increases. Furthermore, the piezoelectric coefficient was 7 pC/N under a low poling field of 1 kV/mm.

Relaxation currents in morphotropic region of Pb[(Fe1/3Sb2/3) x Ti y Zr z ]O3 ferroelectric ceramics

Studies on the dielectric relaxation currents in the morphotropic region of Pb[(Fe1/3Sb2/3) x Ti y Zr z ]O3 with x + y + z = 1, x = 0.1 and y = 0.44–0.46 are presented. The measurements have been performed at three poling fields, i.e. (a) 0.02 kV cm−1 that is much lower than the coercive force (8 kV cm−1), (b) 10 kV cm−1, i.e. slightly above the coercive force and (c) much higher field (20 kV cm−1). There were measured transient polarisation and depolarisation currents. For a low poling field, these currents do not differ from each other, but for higher fields the difference increases with increasing poling field. The analysis of depolarisation current data obtained at various temperatures (298–473 K) shows that relaxation time τp varies exponentially with temperature. The activation energies calculated for samples with y = 0.44, 0.45 and 0.46 equals to 0.26, 0.24 and 0.22 eV, respectively. The defect dipole ) complex and the Dissado–Hill double-minimum potential models are proposed to explain the observed relaxation behaviour in Pb[(Fe1/3Sb2/3) x Ti y Zr z ]O3 ferroelectric ceramics.

Effect of Poling Field and Non-linearity in Quantum Breathers in Ferroelectrics

Lithium tantalate is technologically one of the most important ferroelectric materials with a low poling field that has several applications in the field of photonics and memory switching devices. In a Hamiltonian system, such as dipolar system, the polarization behavior of such ferroelectrics can be well- modeled by Klein-Gordon (K-G) equation. To probe the quantum states related to discrete breathers, the same K-G lattice is quantized to give rise to quantum breathers (QBs) that are explained by a periodic boundary condition. The gap between the localized and delocalized phonon-band is a function of impurity content that is again related to the effect of pinning of domains due to antisite tantalum defects in the system, i.e. a point of easier switching within the limited amount of data on poling field.

Quantum breathers in lithium tantalate ferroelectrics

Lithium tantalate is technologically one of the most important ferroelectric materials with a low poling field that has several applications in the field of photonics and memory switching devices. In a Hamiltonian system, such as dipolar system, the polarization behavior of such ferroelectrics can be well-modeled by Klein–Gordon (K-G) equation. Due to strong localization coupled with discreteness in a nonlinear K-G lattice, there is a formation of breathers and multi-breathers that manifest in the localization peaks across the domains in polarization–space–time plot. Due to the presence of nonlinearity and also impurities (as antisite tantalum defects) in the structure, dissipative effects are observed and hence dissipative breathers are studied here. To probe the quantum states related to discrete breathers, the same K-G lattice is quantized to give rise to quantum breathers (QBs) that are explained by a periodic boundary condition. The gap between the localized and delocalized phonon-band is a function of impurity content that is again related to the effect of pinning of domains due to antisite tantalum defects in the system, i.e., a point of easier switching within the limited amount of data on poling field, which is related to Landau coefficient (read, nonlinearity). Secondly, in a non-periodic boundary condition, the temporal evolution of quanta shows interesting behavior in terms of ‘critical’ time of redistribution of quanta that is proportional to QB’s lifetime in femtosecond having a possibility for THz applications. Hence, the importance of both the methods for characterizing quantum breathers is shown in these perspectives.

Effect of Pozzolanic Materials and Poling Field on Electromechanical Coupling Coefficient of Cement-Based Piezoelectric Composites

Electromechanical coupling coefficient of cement-based piezoelectric composites affected by pozzolanic materials and poling field are investigated. Specimens, through a pressure approach, are manufactured by combining PZT powders and cement-based binder with the same volume fraction. Pozzolanic materials including fly ash, slag and silica fume replace 20% cement in the binder. Three poling fields are considered to induce piezoelectricity of 0-3 cement-based composites. Results show that electromechanical coupling coefficients do not have many fluctuations in terms of material ages for any cement-pozzolanic piezoelectric composites. With the same volumetric substitutes of pozzolanic materials, the electromechanical coupling coefficient with pozzolanic materials except fly ash is lower than that with plain cement, especially for silica fume having a 7.9% decrease. Raising poling field can increase electromechanical coupling coefficients. Polarization of cement-based piezoelectric composites containing silica fume in low poling fields such as 0.5kV/mm and 1kV/mm is not easy to complete.

Influence of Poling Conditions on the Characteristics of PZT Ceramics

In the poling process of PZT ceramics, the poling temperature is a critical condition. When the poling temperature is too low, no matter how high is the poling field and how long is the poling time, the planar electromechanical coupling factor kp is lower. When the poling temperature is higher enough, the kp can reach to a saturated value with a lower poling field and short poling time. The variation of dielectric constant with the poling conditions is the same as that of planar electromechanical coupling factor. When poling with a low temperature, the dielectric constant after poling is lower than 1400. When poling with higher temperature, no matter how high is the poling field and how long is the poling time, the dielectric constant after poling is higher than 1500.

Effect of Polarization on the Microstructure and Piezoelectric Properties of PZT-Cement Composites

Lead zirconate titanate (PZT)-Portland cement (PC) composites were produced and successfully poled at different poling field and time. The effect of polarization on the microstructure and piezoelectric properties were then investigated. It was found that, at a fixed poling field up to 2 kV/mm, the piezoelectric coefficient (d33) was found to increase with poling time. The optimum poling time was found at 45 minutes where d33 value is 42 pC/N. The optimum and most practical poling field found for the composite was at 2 kV/mm. Lower poling field would give the composite lower piezoelectricity and poling field that is too high would result to breakdown of samples. Therefore, from these results, a poling field of 2 kV/mm at 45 minutes would be the ideal polarization condition used in poling PZT-PC composites.

Electro-Optical Properties of Polymers Containing Alternating Nonlinear Optical Chromophores and Bulky Spacers

Alternating polymers of a nonlinear optical chromophore and bulky spacers were synthesized. High chromophore loading and efficient site isolation were achieved with this approach. The effects of chromophore loading density and electric poling field on the electro-optical (EO) properties of the polymers were carefully compared with those of guest−host systems of the same chromophore. The alternating polymer can be poled to higher EO efficiency under a lower poling field than the optimized guest−host system, while the λmax of the polymer film is about 40 nm shorter than that of the guest−host system.

Piezoelectric properties of Mn-doped (Na 0.5Bi 0.5) 0.92Ba 0.08TiO 3 ceramics

Piezoelectric ceramics (Na 0.5Bi 0.5) 0.92Ba 0.08TiO 3+ x mol.% Mn (BNBT-Mn) with x ranging from 0 to 2.97 are synthesized by conventional solid state reaction. The sintered BNBT-Mn exhibited a single phase perovskite structure without detectable secondary phase from x=0 to x=2.6. With increasing amount of doped Mn, the Curie temperature ( T c) of BNBT-Mn decreased rapidly, piezoelectric constants d 33 and k t increased promptly when x was lower than 0.56, taking the maximum value of 160×(10 −12 C/N) and 58.5%, respectively for x=0.56, then decreased slightly with x ranging from 0.56 to 2.6, and finally decreased rapidly for x>2.6, whereas Q m showed a different trend from d 33 and k t. Furthermore, k t had a relatively high value under the low poling field ( E p) for x=0.56 owing to the reduced coercive field ( E c). Possible mechanisms of the influence of Mn doping on the microstructure and piezoelectric properties are discussed.

Indented crack growth during poling of a high displacement PZT material

The present paper presents the effect of poling field on the indented crack lengths and electromechanical properties of a PZT material of high technological interest, because of the relatively large strains it can generate (more than 1%). The tests were performed on bars that could be electrically characterized using electrical resonance. The bars were indented, so that they contained controlled surface cracks. The indentation cracks grew significantly more than twice their initial length during the application of a typical poling field 1.5 kV mm −1. This is a very surprising result compared to the behaviour observed for previously tested PZT materials and it highlights a potentially major problem for the application of the materials with the composition studied. Also of concern is the fact that most of the crack growth occurred at relatively low poling fields (less than 2 kV mm −1). No effect of domain reorientation at the crack tip could be observed and no anisotropy in crack growth appeared during the poling. The behaviour of the piezoelectric coefficient d 31 and the evolution of cracks during poling at different electric fields were not clearly related.

Additive effects on electrical properties of (Bi1/2Na1/2)TiO3 ferroelectric ceramics

Microstructure, dielectric, ferroelectric and piezoelectric properties of bismuth sodium titanate (Bi1/2Na1/2)TiO3 (BNT) were studied for a candidate as lead-free piezoelectric ceramics. In the case of Mn addition, the Curie temperature, Tc, decreases rapidly with increasing amount of doped MnCO3. The resistivity, ρ, is enhanced to 3×1014 (Ωcm) (at 40°C) for BNT+MnCO3 0.2 (wt.%) and electromechanical coupling factor, k33, was obtained the relatively high value under the condition of the low poling field, Ep for the Mn-doped BNT ceramics. It seems that Mn ions exist in the grain, and substitute for the A- or B-site of the perovskite structure, and eject Bi ions to the air.

Real-Time Poling Vapor Co-deposition of Dye-Doped Second-Order Nonlinear Optical Polymer Thin Films

Dye-doped second-order nonlinear optical (NLO) poly(amic acid) (PAA) and polyimide (PI) thin films were prepared via a newly developed real-time poling vapor co-deposition process. This method would plausibly enable many polymeric materials, including high glass transition ones, to be matrix films and many NLO-active chromophores to be desired dopants for making numerous NLO thin films. The PAA film, after curing at 150 °C, showed a considerable improvement in thermal stability. Fourier transform infrared characterization also revealed that a 23 wt % disperse red 1 doped PI thin film exhibited reasonable second harmonic generation (SHG) characteristics even at relatively low poling fields; that is, the SHG coefficient had increased from 0.8 to 5.8 pm/V for a poling field increasing from 0.01 to 0.1 MV/cm.

A real-time poling approach for preparing second-order nonlinear optical polymer thin films

A new real-time poling approach for preparing second-order nonlinear optical (NLO) polymer thin films is presented. The presented method may be conveniently applied to many polymer thin film systems without going through the complicated conventional synthesis and poling procedures. This method, which is proven in this work to be feasible experimentally, is done by simultaneously co-depositing a NLO active dye, disperse red 1 and two polyamide thin film forming monomers on a gold electrodes pre-patterned glass substrate while concurrently applying an electrical field for poling. A second harmonic generation (SHG) signal is detected from the resultant thin films at a very low poling field ranging from 0.01 to 0.1 MV/cm which increases in intensity as the poling field increases.

Molecular and macroscopic NLO properties of organic polymers

AbstractTwo classes of aryltrienes in which the conjugation was incorporated in six‐membered rings have been developed. The microscopic nonlinear susceptibility, μβ, the product of the dipole moment and the second‐order nonlinear susceptibility, of these chromophores were measured using electric field‐induced second harmonic generation (EFISH). The chromophores were then copolymerized as side‐chain pendant groups in a methacrylate backbone copolymer with methyl methacrylate and their macroscopic electrooptic coefficients, r, were experimentally determined using a reflection technique after electric field poling of the polymers. When compared with 4,4′‐N,N‐dimethylaminonitrostibene (DANS), these molecules demonstrated electrooptic activities up to three times of DANS, when measured at 1.3 μm. By using a simple two‐level free‐gas model, the two sets of measurements corresponded closely at low poling fields. At high fields, the simple model breaks down as more detailed poling parameters are required to accurately describe the nonlinear poling effects. The results of the analysis of the high‐field poling data will be published separately. © 1994 John Wiley &amp; Sons, Inc.

Poling dynamics and relaxation of polar order in guest/host polymers by second-harmonic generation

A detailed study of the decay of the second-harmonic generation (SHG) signals of several guest–host nonlinear optical polymer systems has been carried out. The decay of the SHG signal is found to be affected by surface and trapped space charges. A fast component is observed at a low poling field and is found to be mainly due to surface charges which orient the chromophores near the surface. A second component, associated with macroscopic polarization, is induced at high field. The intensity of the second component, which decays considerably slower than the fast component, rapidly increases when the poling field is greater than a threshold voltage. Above the temperature of glass transition Tg, a single exponential function gives a good fit to the shape of the second component of the SHG intensity decay curve. The time constant of the slow component is found to increase with successive poling-decay cycles and reaches a steady-state value after several cycles have been performed. This lengthening effect is found both above and below Tg. Furthermore, the relaxation time of the slow component is also found to depend on the poling field strength: when the host is polymethylmethacrylate, it is found that the relaxation time increases with increasing poling field strength; on the other hand, it decreases with the poling field when polysulfone is used as the host. The temperature dependence of the steady-state relaxation time is not Arrhenius; the Vogel–Fulcher–Tammann equation gives a satisfactory fit to the temperature dependence data.

Effects of Manganese Addition on Piezoelectric Properties of Pb(Zr0.5Ti0.5)O3

The effects of MnO2 addition on k31 and Qm were investigated for Pb(Zr0.5Ti0.5)O3(PZT). The MnO2 addition increased Qm and k31 in a low poling field. This result indicated that Mn-doped PZT possessed properties of `soft' and `hard' piezoelectrics simultaneously. Electron spin resonance measurement indicated that Mn2+, Mn3+ and Mn4+ coexisted in PZT. The tetragonality of the PZT lattice and the Curie temperature decreased with MnO2 content. From these results, it was found that the increase in k31 of Mn-doped PZT was due to the change of the crystal structure toward a cubic system, and the increase in Qm to Mn2+ and Mn3+ ions working as acceptor dopants. The characteristic feature of Mn is that its addition to PZT decreases tetragonality, and various valence states coexist in proper ratio in Mn-doped PZT sintered in atmosphere.

Effects of MnO additions on sintering and piezoelectric properties of Sm-modified lead titanate ceramics

The effect of small additions of MnO (0 to 2 mole %) on sintering of Sm-PbTiO3 ceramics has been investigated. Theoretically dense bodies were achieved at 1150°C by adding 1 mole % MnO, and greater amounts produced a considerable grain growth and density decreasing. The electromechanical behaviour of the sintered ceramics as a function of the MnO content and poling field also was studied, and Kt saturation at relatively low poling fields (50 kV cm-1) only was achieved in samples containing 2 mole % MnO. Although higher Kt values were measured on the denser ceramics a much lower Kt/Kp ratio also was obtained. Sintered ceramics with less dense and larger grain size showed a very small Kp (Kt/Kp ratio higher than 25).

Effect of tricresyl phosphate doping on the remanent polarization in uniaxially oriented poly(vinylidene fluoride) films

Abstract : Uniaxially stretched films of poly vinylidene fluoride were doped (1 wt. %) with plasticizer, tricrecyl phosphate (TCP). This slight doping with TCP was found to enhance the amount of remnant polarization in the region of low poling fields (e.g., from 1 to 6 mC/m2 under Ep =60 MV/m at 20 C) and high poling fields (e.g., from 57 to 66 mC/m2 under Ep = 200 MV/m at 20 C). The pyroelectric coefficient has shown that the doping enhances a quite stable (up to about 140 C) remnant polarization after high field poling (e.g., from 10.2 to 12.5 micro C/m2/K under Ep =200 MV/m at 20 C). This suggestive of a field induced increase in crystallinity. In addition, the switching of quasi-stable dipoles (those which randomize in the 90-140 C range) takes place at much lower electric fields than in undoped films. The present data suggest that a small amount of dopant in the noncrystalline regions greatly enhances ferroelectric dipole switching, possibly by acting in the interfacial zone between crystalline and amorphous regions.