Influence of poling conditions on the piezoelectric properties of PZT ceramics

The influence of the poling temperature, the poling electric field, the poling time and the distance between electrodes on the dielectric constant _r and the electro-mechanical coupling factor k_r of PZT were investigated using a statistical analysis method. Interactions between various factors affecting _r and k_r parameters were found particularly, with regard to the poling temperature. The k_r value of PZT is influenced more by the absolute voltage than by the applied electric field strength.     

铈掺杂对PZT压电陶瓷性能的影响

研究了铈掺杂对PZT(锆钛酸铅)压电陶瓷材料的相组成、微观结构、介电性能、压电性能及铁电性能的影响,并对实验结果做出物理机理的解释.实验结果表明,适量的铈掺杂有利于材料结构的致密,提高了体电阻率,解决了材料在高温高场下极化困难的问题,在铈掺杂量为0.4%(摩尔分数)时,制备出综合性能良好的PZT压电陶瓷:室温时εr=958,tgδ=0.24%,d33=239pC/N,Kp=0.45,Qm=886,适合制备大功率压电陶瓷.     

Effect of electrical and mechanical poling history on domain orientation and piezoelectric properties of soft and hard PZT ceramics

Abstract

The superior piezoelectric properties of all polycrystalline ferroelectrics are based on the extent of non-180° domain wall motion under electrical and mechanical poling loads. To distinguish between 180° and non-180° domain wall motion in a soft-doped and a hard-doped lead zirconate titanate (PZT) ceramic, domain texture measurements were performed using x-ray and neutron diffraction after different loading procedures. Comparing the results to measurements of the remanent strain and piezoelectric coefficient allowed the differentiation between different microstructural contributions to the macroscopic parameters. Both types of ceramic showed similar behavior under electric field, but the hard-doped material was more susceptible to mechanical load. A considerable fraction of the piezoelectric coefficient originated from poling by the preferred orientation of 180° domains.     

铟掺杂PZT铁电陶瓷性能研究

采用传统固相烧结法制备In2O3掺杂的锆钛酸铅(PZT)铁电陶瓷,研究了In2O3掺杂量对PZT铁电陶瓷材料的相组成、微观结构、介电性能、压电性能及铁电性能的影响。研究结果表明,随着In2O3掺杂量的增加,PZT材料在准同型相界处三方相增加四方相减少,适量掺入In2O3有利于晶粒均匀生长。在不同的铟掺杂剂量下,PZT陶瓷材料分别具有最佳的铁电及压电性能。当铟掺杂量为0.1%(质量分数)时,PZT材料具有最佳的铁电性能,其剩余极化强度为23.43μC/cm2,矫顽场为9.783kV/cm。当铟掺杂量为0.3%(质量分数)时,PZT材料具有最好的压电性能,其tanδ=0.023,d33=540pC/N,εr=1513,Kp=0.764,Qm=1819。     

Dielectric and piezoelectric properties of the mechanochemically prepared PZT ceramics

Mechanochemical synthesis was applied to obtain nanocrystalline powders of composition Pb(Zr_0.52Ti_0.48)O₃ (PZT). Milling was performed in a planetary ball mill using vials and balls made of zirconia or steel in order to investigate influence of milling media on the electrical properties of resulting ceramics. PZT ceramics showed high values for dielectric constant (∈_r), reaching 970 at room temperature, as well as low dielectric loss (tanδ) under the optimal processing conditions. High values of remanent polarization (P _r) indicate high internal polarizability. The best samples showed piezoelectric strain constant d ₃₃ = 347 pC/N and planar coupling factork _P = 0.44. Milling in ZrO₂ medium prevents powder contamination and provides reproducibility of milling process. Also, PZT obtained from the powders milled in ZrO₂ exhibited lower values of dielectric loss, in comparison with the PTZ obtained from the powders milled in Fe. This suggests that contamination of the powder with Fe could result in an increase of conductivity in final product.     

PZT系梯度功能压电驱动器的谐响应特性

研究了PZT系梯度功能压电驱动器谐振状态的机电响应特性，通过改变驱动电场和频率，研究其谐振频率和顶端位移的变化特性。结果表明：增加电场，谐振频率减小，谐振点位移增大，并逐渐趋向饱和。在谐振点附近，悬臂梁弯曲位移达到最大值。     

Enhancement of piezoelectric properties and temperature stability by forming an MPB in KNN-based lead-free ceramics

0.92(Na_0.51K_0.49?x Li _x )NbO₃–0.02Bi_0.5K_0.5TiO₃–0.06BaZrO₃ (x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) lead-free piezoelectric ceramics were prepared by solid state reaction route. The effect of Li doping amount on the structure and electrical properties of the ceramics were investigated. All ceramics had pure perovskite structure, while the crystallographic symmetry changed from rhombohedral to tetragonal with the increase of Li doping amount. A PZT-like morphotropic phase boundary (MPB) with the coexistence of rhombohedral and tetragonal phases was identified in the composition of x = 0.03. As expected, the ceramics of the MPB composition showed optimal properties: piezoelectric coefficient d ₃₃ = 227 pC/N, planar electromechanical coupling coefficient k _p = 39.3 %, dielectric permittivity $ \varepsilon_{33}^{T} /\varepsilon_{0} $  = 1,640, dielectric loss tanδ = 2.0 %, remnant polarization P _r = 13.3 μC/cm², coercive field E _c = 1.53 kV/mm, and Curie temperature T _c = 253 °C. Together with good temperature stability to 200 °C, this KNN-based lead-free ceramics should be very promising for practical applications.     

The effects of sintering temperature and poling condition on the piezoelectric properties of 0.935(Bi0.5Na0.5)TiO3 - 0.065BaTiO3 ceramics

The 0.935(Bi_0.5Na_0.5) TiO₃ -0.065BaTiO₃ (abbreviated as BNT6.5BT) lead-free ceramics were prepared by conventional solid state sintering technique. The effects of sintering temperature (1150–1200 °C) and poling condition on its piezoelectric properties were examined. Piezoelectric properties like the piezoelectric constant (d₃₃) and electromechanical factors (k _p , k _t ) depend on the poling field and poling temperature, whereas different poling times, in the 5–30 min range, were not observed to have any significant effect on the piezoelectric properties. With respect to piezoelectric properties, the chosen sintering temperature range is suitable for BNT6.5BT ceramics.     

A model for the structural hysteresis in poling and thermal depoling of PZT ceramics

A structural hysteresis associated with domain orientation during poling and thermal depoling of lead titanate zirconate (PZT) ceramics has been observed. The poled materials appear to lose their piezoelectric properties at a temperature somewhat below the Curie temperature and yet the domain configurations remain unchanged. The above phenomenon is successfully explained by a model which predicts that upon thermal depolarization, poled ceramics undergo transformation from the poled state into the antiferroelectric state before returning back to their original unpoled state.     

Structure and magnetoelectric properties of Gd-doped La0.7Ca0.3MnO3 polycrystalline ceramics

Journal of Materials Science: Materials in Electronics - The temperature coefficient of resistance (TCR) and magnetoresistive (MR) properties of materials have a large impact on the performance of...     

Composition and temperature dependence of the dielectric, piezoelectric and elastic properties of pure PZT ceramics

Pure (undoped) piezoelectric lead zirconate titanate (PZT) ceramic samples at compositions across the ferroelectric region of the phase diagram were prepared from sol-gel-derived fine powders. Excess lead oxide was included in the PZT powders to obtain dense (95-96% of theoretical density) ceramics with large grain size (>7 mum) and to control the lead stoichiometry. The dielectric, piezoelectric, and elastic properties were measured from 4.2 to 300 K. At very low temperatures, the extrinsic domain wall and thermal defect motions freeze out. The low-temperature dielectric data can be used to determine coefficients in a phenomenological theory. The extrinsic contribution to the properties can then be separated from the single-domain properties derived from the theory.     

Effect of lanthanum-doping on the dielectric and piezoelectric properties of PZN-based MPB composition

In this paper, effect of lanthanum doping on the dielectric and piezoelectric properties of the morphotropic phase boundary (MPB) composition in the Pb(Zn_1/3Nb_2/3)O₃-BaTiO₃-PbTiO₃ system is presented. Samples were prepared according to the formula Pb_0.85–x Ba_0.15La _x [(Zn_1/3Nb_2/3)_0.7Ti_0.3]_1–x/4O₃ (0 < x < 0.3), where the compensation for La ions was achieved via the appearance of B-site vacancies. All the compositions were synthesized using columbite precursor method and sintered using inverted crucible approach. Results of x-ray diffraction demonstrate that the solid solubility limit of La₂O₃ in the PZN-based MPB composition is more than 30 mole%. Incorporation of La₂O₃ into A-site sublattice of perovskite structure stabilizes rhombohedral phase against tetragonal phase, as a consequence, the location of the MPB composition range is displaced toward PT-rich end. In addition, the lattice distortion degree, represented by either tetragonality for tetragonal phase or rhombohedrality for rhombohedral phase, is reduced. Increasing La₂O₃ content remarkably decreases both the dielectric permittivity maximum and the temperature of the dielectric permittivity maximum. However, addition of La₂O₃ obviously strengthens the degree of the frequency-dispersion, which is correlated with the weakened degree of ferroelectric couplings among oxygen octahedra. The degree of diffuse phase transition (DPT) is prominently enhanced with increasing La₂O₃, for which the underlying mechanism is explored. Moreover, the ever-increasing extent of departure from Curie-Weiss behaviour induced by the lanthanum doping is indicative of some changes with the respect to the scale of polar microregions inherent to relaxors. The longitudinal piezoelectric coefficient (d ₃₃) is maximized at 1 mole% La₂O₃, which is attributed to the combined effect of phase coexistence and enhanced contribution from non-180° domain wall process associated with rhombohedral phase.     

铬掺杂对PZN-PZT陶瓷微观结构和电学性能的影响

研究了Cr2O3掺杂对0．2Pb（Zn1／3Nb2/3）O3-Pb（Ti0.5Zr0.5）03（PZN-PZT）陶瓷结构和电学性能的影响。结果表明,Cr2O3掺杂量小于0．3wt％时,Cr2O3能引起三方-四方相变,四方相含量诸加,晶粒尺寸和烧结密度上升;掺杂量高于0．3wt％时,Cr2O3掺杂能抑制晶粒长大并降低烧结密度。同时,Cr2O3掺杂表现出硬性掺杂特征：εr变小,Qm值增加。而tanδ,kp和d33随Cr2O3掺杂量增加而表现出极值特征。最佳的压电性能出现在Cr2O3掺杂量为0．3wt％处。     

PZT含量对PZT-PZN-PNN压电陶瓷材料电性能的影响

采用传统固相法制备了xPb（Zr0.52Ti0.48）O3-（1-x）{Pb（Zn1/3Nb2/3）O3-Pb（Ni1/3Nb2/3）O3}（简称PZT-PZN-PNN）四元系压电陶瓷，研究了不同PZT含量对PZT-PZN-PNN陶瓷的相结构、显微结构、压电性能和介电性能的影响。结果表明：材料的压电常数（d33）、机电耦合系数（％）和介电常数（曲随着PZT含量的增加先增大，后减小，当PZT含量为0.83时，其值达到最大值；随着PZT含量的增加，材料的机械品质因数（Qm）逐渐增大，谐振电阻僻（Rf）和介电损耗（tanδ）逐渐减小。当PZT含量为0.83时，四元系PZT-PZN-PNN压电陶瓷在较低的烧结温度（1000℃）下烧结，其主要的电性能参数如下：d33=477pC/N，Kp=0.71，Qm=98，εf=2228，tanδ=0.0070，Tc=325℃，根据双晶片对压电陶瓷材料的性能要求，该纽份可作为纺织机械中选针器用压电双晶片的侯选材料。     

Thermodynamic properties of the superconductorsBaPb 0.7 Bi 0.3 O 3 andBa 0.7 K 0.3 BiO 3 using Eliashberg theory

We present results of a thermodynamic analysis for the superconductors compounds BaPb_0.7Bi_0.3O₃ and Ba_0.7K_0.3BiO₃. The physical quantities are calculated making use of the Eliashberg theory and the electron-phonon spectra ²()F() as calculated by Shirai et al. For the superconductor BaPb_0.7Bi_0.3O₃, several models of the ²()F() were studied looking for a better agreement with experimental data. The best fit is achieved with a simple constant scaling (C = 1.25) of the Shirai's spectra. The functional derivative of the deviation function D(t) with respect to changes in ²()F() is also calculated.     

The effect of poling treatment and crystal structure of PZT on fracture toughness and fatigue resistance

Empirical measurements of fracture toughness and fatigue strength were conducted for piezoelectric Pb(Zr _x ,Ti_{1 – x} )O₃ of various compositions such as tetragonal, MPB, and rhombohedral. Before the poling treatment the rhombohedral showed the highest fracture toughness, while the tetragonal revealed the lowest fracture toughness. After poling treatment, the fracture toughness measured by the pre-cracked SENB method decreased in all three compositions. The most remarkable decrease was observed in the tetragonal composition. However, when the indentation strength method was used the highest fracture toughness was observed in the tetragonal. The stress intensity factor relief due to microcracks around the indentation marks and the anisotropic internal stresses caused by domain alignment during the poling treatment were proposed as explanations for the comflicting results. Fatigue resistance was lowered by the compressive stress introduced during the poling treatment. The highest fatigue resistance was observed in the rhombohedral composition of low tetragonality, which exhibited low internal stress.     

The effect of sintering on the properties of Ba0.7Sr0.3TiO3 ferroelectric films produced by electrophoretic deposition

Ba_0.7Sr_0.3TiO₃ (BST) films were produced on metal substrate using electrophoretic deposition (EPD) followed by high temperature sintering. The composition, crystal structure and microstructure of the deposited films were characterised using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The sintered BST films showed a sharp perovskite structure with uniform microstructure. The results indicated that a typical BST film of 20 μm thick after sintering for 2–10 h exhibited the relative dielectric constant ranging from 3100 to 5100 at 20 °C and dissipation factor of 0.061–0.118 at 1 kHz. The density, crystallinity, microstructural uniformity and dielectric properties of the BST films reached their best values after 8 h annealing at 1350 °C. These films also possess excellent adhesion to the substrate.     

Size effect on piezoelectric properties of barium stannate titanate ceramics prepared from nanoparticles

Piezoelectric properties of Ba(Ti_1?x Sn _x )O₃ ceramics with x = 0.025, 0.045 and 0.065, prepared from 16 nm powders, were compared with those of the corresponding ceramics obtained from 86 nm powders to see the effect of tin content and particle size of the starting powders. Ba(Ti_1?x Sn _x )O₃ powders were synthesized by solid state reaction of BaCO₃, TiO₂ and SnO₂ at 1,050 °C. The powders were high energy ball milled to produce nanocrystalline powders having average particle size of 16 nm. The milled powders were sintered at 1,350 °C for 4 h to yield ceramics. For these ceramics, increasing Sn content from x = 0.025–0.065 produces a decrease in (1) unipolar strain level s from 0.084 to 0.027 %, and (2) electromechanical coupling factor k _p from 33.6 to 19.3 %. However, the bulk density, room temperature dielectric constant and piezoelectric charge constant d ₃₃ exhibit an increase from 5.03–5.84 g/cm³, 1,342–2,156 and 7–110 pC/N, respectively, with increasing Sn content. The increasing trend of density and d ₃₃ presently observed is in sharp contrast to the result of corresponding ceramics prepared from 86 nm nanopowders. The present study reveals a cooperative mechanism involving both the nanoscale size of the starting particles and optimum tin content which results in the enhancement of d ₃₃ with tin content.