Domain switching characteristics of lead zirconate titanate piezoelectric ceramics on a nanoscopic scale

Domain switching characteristics of lead zirconate titanate ceramics with and without poling under compressive loading are investigated using electron backscatter diffraction. For loading in the poling direction, the switching strain is stronger than that for loading perpendicular to the poling direction. There is strong domain switching when the domain (c-axis of the tetragonal structure) is orientated close to the loading direction. A large number of domains are switched between 85.4° and 90.0°, with many crossing the loading axis. Each grain consists of domains with three different patterns; i.e., with c-axis orientated in three directions in each grain. The patterns remain unchanged even with domain switching and strong deformation. However, the ratios among the patterns depend on compressive stress. Under stress, one or two specific domain modes are switched to about 90°, although others are not switched as much. These domain switching characteristics are related to the poling and loading directions. 90° domain switching model is proposed on the basis of twin deformation model. Due to the aspect ratio of c/a = 1.014 (tetragonal structure), the angle of the switching is less than 90° (89.2°). This angle is corresponding to the switching angle obtained by an electron backscatter diffraction analysis (Ave. 88.9°).     

Impact of Sr-doping on structural and electrical properties of Pb(Zr0.52Ti0.48)O3 thin films on RuO2 electrodes

In this paper, we investigated the impact of Sr-doping on the structural properties and electrical characteristics of lead zirconate titanate [Pb(Zr_0.52Ti_0.48)O₃, PZT] thin films deposited on RuO₂ electrodes by a sol-gel process and spin-coating technique. We used X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and field-emission transmission electron microscopy to explore the structural, morphological, chemical, and microstructural features, respectively, of these films as a function of the growth condition (strontium doping concentrations varied from 1, 3, and 5 mol%). The PZT thin film processed at the 3 mol% Sr exhibited the best electrical characteristics, including a low leakage current of 2.27×10⁻⁷ A/cm² at an electric field of 50 kV/cm, a large capacitance value of 2.74 μF/cm² at a frequency of 10 kHz, and a high remanent polarization of 37.95 μC/cm² at a frequency of 5 kHz. We attribute this behavior to the optimal amount of strontium in the PZT film forming a perovskite structure and a thicker interfacial layer at the PSZT film-RuO₂ electrode interface.     

Investigation of frequency effect on electrical fatigue and crack tip domain-switching behaviors in Pb(Mg1/3Nb2/3)0.65Ti0.35O3 ceramics via synchrotron X-ray diffraction

The effect of frequency on the electrical fatigue, crack growth and domain switching in Pb(Mg_1/3Nb_2/3)_0.65Ti_0.35O₃ ceramics has been investigated. The changes in microstructure, ferroelectric properties and domain-switching behavior of samples fatigued at 1, 10, 50 and 100 Hz were determined. In this experiment, we found that the thickness of the damaged layer under the electrodes and the crack length decrease with increasing frequency. The remnant polarization decreases while the coercive field increases with an increasing number of loading cycles. A domain orientation map around the crack tip was revealed using scanning high-energy X-ray diffraction from a synchrotron source. This showed the effect of fatigue frequency on the lattice strain distribution and ferroelectric domain texture around the crack tip.     

Multi-type nanoscale domain switching dynamics in tetragonal PIN-PMN-PT single crystal under electrical bias

Domain switching coupled with polarization reorientation allows ferroelectrics to exhibit high potential for use in nonvolatile memories, electro-optic devices, and nanoelectronics. Although several studies have elucidated domain switching, the research on switching dynamics of complex nanoscale domain structures in relaxor-based ferroelectric materials has been lacking. Herein, the domain structure and domain switching dynamics in tetragonal PIMN-PT single crystals were systemically studied via piezoresponse force microscopy. An interlocking multi-type domain pattern comprising irregular 180° ferroelectric domains and regular 90° ferroelastic domains was observed and its formation mechanism was explored. Different domain switching dynamics of field-dependent responses were investigated. The results indicate that T-phase PIMN-PT single crystals exhibit a hierarchical domain switching process. Under a low electrical-bias stimuli (<10 V), the nucleation and growth of 180° domains dominate the switching process. By increasing the electrical bias from 10 V to 80 V, 90° domain switching was gradually completed and the sample achieved a single-domain state. The nucleation and growth mechanism of ferroelectric domains under electrical-bias stimuli were also discussed. Overall, our results deepened the understanding of ferroelectric switching in complex nanoscale domain structures and facilitate the use of precise domain tailoring technology for fabricating T-phase relaxor-based ferroelectric single crystals.     

The effect of flexoelectricity on domain switching in the vicinity of a crack in ferroelectrics

Ferroelectrics are widely used in the manufacture of transducers, actuators, and memory devices, due to their attractive electromechanical properties. However, the reliability and failure of devices is greatly dependent on their brittleness. In view of the fact that both the polarization distribution and elastic field are at nanoscale and vary greatly in the vicinity of the crack tip, flexoelectricity is expected to strongly affect the domain configuration. In this work, Ginzburg-Landau (TDGL) theory and the phase field method (PFM) are employed to analyze the influence of flexoelectric effect on the domain switching process in the vicinity of the crack tip of ferroelectric materials. The results obtained show that, the domain configuration would become asymmetric with increasing flexoelectric coefficients, and the flexoelectric effect has a larger influence on the polarization field than on the elastic field in the vicinity of the crack tip of ferroelectric materials.     

Investigation of the mechanism of domain switching in different Na0.5Bi0.5TiO3 microstructures

Several researches have studied the physical properties of hydrothermally-synthesized low dimensional piezoelectric nanostructures. However, the obtained piezoelectric coefficient is not high and the relationship between physical properties and microstructures is still neglected. Here we report the piezoelectric and ferroelectric properties of different lead-free sodium bismuth titanate (Na_0.5Bi_0.5TiO₃, NBT) microstructures synthesised with hydrothermal routes and give visualization of domain structures using piezoresponse force microscopy. The NBT nanowire exhibits better local piezoelectric response compared with NBT spherical aggregates and microcubes and other one-dimensional materials prepared by hydrothermal method and the large piezoelectric coefficient of nanowire was explained by observed regular stripe domain structures. Moreover, it is found that there are different domain configurations at the top and side of the nanowire under the external electrical fields, which don't change the regular stripe domain structure but lead to the movement of domain boundaries. By finite element modeling, it attributes to the different electric potential distributions from tip within the nanowire.     

Multi-step domain switching and polarization fatigue in [110]-oriented 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 single crystals

Domain switching in ferroelectrics is at the heart of many functionalities, and the visualization of switching pathway is the key to understand the fundamental properties and to promote the applications of high-performance ferroelectrics. Here, we directly documented the multi-step domain switching in [110]-oriented 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-0.33PT) single crystals under a cycling electric field with the help of in situ polarized light microscopy. Based on the characteristic domain configuration analysis, we demonstrated that the 180° switching process was consisted of multi-step 60° switching. Such a multi-step 60° switching pathway resulted in a large negative strain and an internal electric field, which contributes to a large polarization fatigue rate under the alternating electric field. Our works may provide a window to study the domain switching process and its effect on polarization fatigue in relaxor-ferroelectric single crystals.     

Electrical fatigue behavior of lead zirconate titanate ceramic under elevated temperatures

The electrical fatigue behavior of lead zirconate titanate (PZT) ceramics is investigated under different temperatures. A bipolar triangular electric field with the amplitude of ±1.5 kV/mm and the frequency of 50 Hz is applied to samples up to 1 × 10⁶ cycles. The fatigue rate is found to be temperature dependent, and the fatigue degradation is represented by the loss of remnant polarization, dielectric constant, and piezoelectric constant increased with loading cycle numbers. The degradation, involving surface damage and crack propagation, is more pronounced in samples cycled at lower temperatures, and increases with increasing number of cycles. The temperature effect on fatigue degradation of the properties is described based on the field shielding effect caused by surface damage and fatigue-induced cracks. The effect is more dominant in case of higher cycling numbers and lower temperature fatigue due to higher strain mismatch between switchable and non-switchable domains. Moreover, Raman spectroscopy is used to determine the influence of fatigue on the ferroelectric domains in different areas of the specimens.     

Impact of fatigue behavior on energy storage performance in dielectric thin-film capacitors

The polarization hysteresis loops and the dynamics of domain switching in ferroelectric Pb(Zr_0.52Ti_0.48)O₃ (PZT), antiferroelectric PbZrO₃ (PZ) and relaxor-ferroelectric Pb_0.9La_0.1(Zr_0.52Ti_0.48)O₃ (PLZT) thin films deposited on Pt/Ti/SiO₂/Si substrates were investigated under various bipolar electric fields during repetitive switching cycles. Fatigue behavior was observed in PZT thin films and was accelerated at higher bipolar electric fields. Degradation of energy storage performance observed in PZ thin films corresponds to the appearance of a ferroelectric state just under a high bipolar electric field, which could be related to the nonuniform strain buildup in some regions within bulk PZ. Meanwhile, PLZT thin films demonstrated fatigue-free in both polarization and energy storage performance and independent bipolar electric fields, which are probably related to the highly dynamic polar nanodomains. More importantly, PLZT thin films also exhibited excellent recoverable energy-storage density and energy efficiency, extracted from the polarization hysteresis loops, making them promising dielectric capacitors for energy-storage applications.     

Influence of graphite on the low-frequency fatigue behavior of zirconium diboride ceramics

The fatigue behavior of a ZrB₂-based ceramic containing SiC and graphite was compared to a ZrB₂-SiC reference material based on bending testing, quantitative calculations as well as crack growth and fracture characterization. The addition of graphite flake makes ZrB₂-SiC-Graphite ceramics exhibit fatigue failure behavior at very high stress level (93% of the characteristic strength, σ₀), owing to the increased K_Ic promoted by crack deflection, bridging, bifurcation and pull-out of graphite, while the fatigue behavior of ZrB₂-SiC appears when the maximum stress is below ~86%σ₀. However, both the slow crack growth exponents of the graphite containing ceramic, n and nc values, which reflect the fatigue resistance in static and cyclic fatigue conditions, respectively, are only 1/4 as compared to the reference graphite-free ceramic. This may be due to the weak boride/graphite interfaces, which lead to the decrease of the initial critical stress intensity factor (K_c-initial) value from 2.6 to 2.0 MPa m^1/2.     

Investigations of domain switching and lattice strains in (Na,K)NbO3-based lead-free ceramics across orthorhombic-tetragonal phase boundary

Various strain contributions of (Na_0.52K_0.48 − x)(Nb_0.92 − xSb_0.08)O₃− xLiTaO₃ ceramics in the proximity of orthorhombic (O) and tetragonal (T) polymorphic phase boundary (PPB) were quantitatively resolved by means of synchrotron x-ray diffraction together with macroscopic strain measurements. Compared with O-rich compositions with a governing mechanism of intrinsic lattice strains, T-rich compositions exhibited a dominant strain mechanism from reversible domain switching. Quantitative analysis of diffraction data suggested that extrinsic strain contributions should depend on not only the lattice distortion δ, but also the poling texture Δf, phase content (for PPB compositions) and domain types. Smaller lattice distortion and higher poling texture tended to enhance the number of irreversible domain switching in O-rich compositions, thus leading to larger fraction of intrinsic lattice strain contribution. The calculated results demonstrated that the product of two parameters Δf and δ would give a reliable estimation of domain-switching strains for T-phase compositions but an overestimation for O-phase compositions.     

Effect of milling time and pH on the dispersibility of lead zirconate titanate in aqueous media for inkjet printing

Micrometre-sized Pb(Zr_0.53Ti_0.47)O₃ (PZT) powder was dispersed in water, stabilized with the ammonium polyacrylate (PAANH₄) and milled to reduce the particle size. The influence of the pH, the amount of PAANH₄, and the milling time on the zeta potential, the PZT particle size and the particle size distribution was studied. The agglomeration took place regardless the milling time at pH 3. The suspension, containing 5 vol.% of PZT and 5 wt.% of PAANH₄, milled at pH 10 for 240 min, was stable and contained particles with a narrow, log-normal particle size distribution with the median size of 160 nm. The dissociated carboxyl groups from the PAANH₄ interacted with the PZT particles as evidenced by Fourier transform infrared spectroscopy and electrosterically stabilized the particles in water at pH 10. The PZT particle size and the stability of the suspension fitted the requirements for the ink, suitable for ink-jet printing.     

Effect of pore size and porosity on piezoelectric and acoustic properties of Pb(Zr0.53Ti0.47)O3 ceramics

We studied the effect of porosity and pore morphology on the functional properties of Pb(Zr_0.53Ti_0.47)O₃ (PZT) ceramics for application in high frequency ultrasound transducers. By sintering a powder mixture of PZT and polymethylmetacrylate spherical particles (1.5 and 10?μm) at 1080°C, we prepared ceramics with ～30% porosity with interconnected micrometer sized pores and with predominantly ～8?μm spherical pores. The acoustic impedance was ～15?MRa for both samples, which was lower than for the dense PZT. The attenuation coefficient α (at 2.25?MHz) was higher for ceramics with ～8?μm pores (0.96?dB?mm^??1?MHz^??1), in comparison to the ceramic with smaller pores (0.56?dB?mm^??1?MHz^??1). The high α value enables the miniaturisation of the transducer, which is crucial for medical imaging probes. The dielectric and piezoelectric coefficients, polarisation, and strain response decreased with increased porosity and decreased pore/grain size. We suggest a possible role of pore/grain size on the switching behaviour.     

Effect of nickel electroplating on the electrical properties of PMZNT relaxor ferroelectrics

Effect of nickel electroplating on insulation resistance and ferroelectricity of PMN-based relaxor ferroelectrics was investigated by resistivity and hysteresis measurements. Annealing experiments on the degraded specimens in air and argon at high temperature were also conducted. It was found that the insulation resistivity of the specimens and the hysteresis characteristic deteriorated after electroplating. Annealing experiments indicated that the degraded samples can recover totally through air annealing above 600 °C for 1 h while the argon annealing had almost no improvement on the degradation. It suggested that some metal elements in the PMN-based ferroelectrics may be reduced by hydrogen produced during electroplating thereby, oxygen vacancies and free electrons were generated, which led to the electrical degradation of the ceramics.     

热压烧结对锆钛酸铅镧陶瓷电卡效应的影响

探讨热压烧结工艺对PLZT(锆钛酸铅镧)陶瓷材料介电击穿性能、饱和极化强度以及电卡性能的影响。通过X射线衍射和扫描电子显微镜,分析陶瓷样品的相组成和微观结构。结果表明,热压烧结法有助于控制陶瓷晶粒的生长,提高陶瓷的致密度并增大陶瓷的介电击穿场强,从而有效提高陶瓷的电卡性能以及电卡转换效率。在328 K(55℃)与478 K(205℃)附近,分别发生低温铁电三方相到高温铁电三方相的相变(FRL-FRH)以及高温铁电三方相到立方顺电相(FRH-Pc)的相变,展现了比较好的弛豫性,在室温下达到3.6 K的绝热温变与1.8×0-7(K·m)/V的电卡转换效率,具有良好的电卡性能。     

Direct-Write Fabrication of Pb(Nb,Zr,Ti)O3 Devices: Influence of Paste Rheology on Print Morphology and Component Properties

Lead niobium zirconate titanate (PNZT) pastes with tailored rheological properties have been developed for direct-write fabrication of thick-film capacitor elements in highly integrated, multifunctional electroceramic devices. Such pastes exhibited pseudoplastic behavior with a low shear apparent viscosity of roughly 1 × 10⁶ cP. On aging, the degree of shear thinning and the low shear apparent viscosity decreased. Pastes prepared from as-received powders attained printable, steady-state viscosities of ∼2 × 10⁵ cP after 50 days of aging. In contrast, pastes prepared from dispersant-coated powders showed no measurable rheological changes after 1 day of aging. Square elements were patterned on dense alumina substrates or Teflon sheets. Leveling behavior as a function of time for single line prints, and the resulting surface topographies of dried PNZT films were measured by laser profilometry. PNZT layers sintered at varying temperatures between 950° and 1050°C for 5 h in either air or a lead-rich atmosphere yielded porous microstructures as revealed by scanning electron microscopy (SEM). Such layers exhibited dielectric constants ( K ) of 1400–1570 at 1 kHz with dissipation factors ( D ) of less than 4.1%.     

Influence of Microstructure on the Dielectric and Piezoelectric Properties of Lead Zirconate-Polymer Composites

Composites with 0–3 connectivity were fabricated from lead zirconate titanate (PZT) and phenolic resin powders. These composites were investigated for dielectric and piezoelectric properties with variations in active particle density and PZT-polymer interface porosity. The dependence of dielectric and piezolectric properties on interface porosity is discussed, especially in terms of porosity factors. The dependence of the piezoelectric constant on interface porosity was greater than that of the dielectric constant. The interface pores play the role of a stress buffer. Thus local stress applied on PZT particles in the composites was remarkably diminished. When particle porosity was high, the dependence of the dielectric and piezoelectric constants on interface porosity decreased.     

Influence of PbO content on the dielectric failure of Nb-doped {100}-oriented lead zirconate titanate films

A series of niobium-doped, {100} textured, “gradient free,” lead zirconate titanate (PNZT) films with different PbO contents were fabricated by the chemical solution deposition method. The films’ PbO content was controlled by changing the average PbO content in the solution from 114.7 to 117 at.%. During the dielectric breakdown process of 1.5 μm thick PNZT films with Pt top and bottom electrodes, two phenomena were observed: cracking and thermal breakdown of the piezoelectric film. At 150°C, with an applied 400 kV/cm electric field, the crack density of PNZT films induced by electromechanical failure increased from 0.060/μm to 0.090/μm as the solution's PbO content increased from 114.7% to 117%. In addition, the films showed higher crack densities and more frequent thermal breakdown events when the electric field was oriented downward (from top to bottom electrode) compared with an upward oriented electric field (from bottom to top electrode). The films with higher PbO content had a lower breakdown strength. Also, all films showed lower breakdown strength when measured in the field down direction. The Schottky barrier height (SBH) decreased from 0.82 ± 0.06 to 0.68 ± 0.04 eV in the field up direction measurement as the PbO content increased. The SBH value did not show significant change in the field down direction measurement. This suggests that the asymmetry in the film/electrode interfaces is a function of the PbO content in the original solution.     

Influence of Fe2O3 addition on the densification and oxygen ion conductivity of the GdSmZr2O7 ceramic

The influence of Fe₂O₃ addition as a sintering aid on the microstructure and electrical properties of the GdSmZr₂O₇ ceramic has been studied. The GdSmZr₂O₇ ceramic with 1 wt.% Fe₂O₃ is composed of a pyrochlore-type phase and a small amount of Gd_0.5Sm_0.5FeO₃. Fe₂O₃ is found to be an effective sintering aid for the GdSmZr₂O₇ ceramic, and a reduction in the sintering temperature of about 200 K is achieved. The total conductivity of the GdSmZr₂O₇ ceramic incorporated with or without 1 wt.% Fe₂O₃ obeys the Arrhenius relation. At 1173 K, the highest total conductivity of the GdSmZr₂O₇ ceramic with 1 wt.% Fe₂O₃ is about 20% higher than that of the GdSmZr₂O₇ ceramic. The GdSmZr₂O₇ ceramic with or without 1 wt.% Fe₂O₃ is an oxide-ion conductor in the oxygen partial pressure range of 1.0 × 10⁻⁴ to 1.0 atm at all test temperature levels.     

电疲劳对掺镧锆钛酸铅陶瓷电致畴变行为的影响

在不同电疲劳周次下,对未极化掺镧锆钛酸铅铁电陶瓷在不同直流电场加载下得到的原位X射线衍射(XRD)谱和撤掉不同直流电场后得到的非原位XRD谱的(002)与(200)晶面衍射峰强与电场强度(EA)的关系进行研究。通过计算90°畴变体积分数发现,在电疲劳过程中,电场撤掉前后的90°畴变体积分数均随EA呈蝶形曲线变化。在低电场作用下,铁电畴更趋向于沿平行试样表面方向,而在EA=2 000 V/mm作用下,当电疲劳至106时,材料中有约5%的铁电畴被钉扎,有约6%的铁电畴在电场撤掉瞬间转回平行试样表面方向。电场撤掉后的90°畴变体积分数能直接反映铁电材料剩余极化程度。