Visualization of highly graded oxygen vacancy profiles in lead-zirconate-titanate by spectrally resolved cathodoluminescence spectroscopy

The ultraviolet and visible cathodoluminescence (CL) emitted at room temperature from bulk hard lead-zirconate-titanate polycrystalline perovskite has been systematically collected before and after an annealing cycle conducted in a reducing atmosphere. Spectroscopic assessments have been made of the in-depth stoichiometric profile developed upon annealing from the sample surface toward the subsurface. Trapping of electronic charge and local atomic scale distortions in the perovskite oxygen octahedron influences the variation observed in visible CL emission, while lattice distortions upon annealing directly arise from the formation of oxygen vacancies

Investigation of the effect of temperature on aging behavior of Fe-doped lead zirconate titanate

The aging degradation behavior of Fe-doped Lead zirconate titanate (PZT) subjected to different heat-treated temperatures was investigated over 1000 h. The aging degradation in the piezoelectric properties of PZT was indicated by the decrease in piezoelectric charge coefficient, electric field-induced strain and remanent polarization. It was found that the aging degradation became more pronounced at temperature above 50% of the PZT’s Curie temperature. A mathematical model based on the linear logarithmic stretched exponential function was applied to explain the aging behavior. A qualitative aging model based on polar macrodomain switchability was proposed

Effects of frequency on electrical fatigue behavior of ZnO-modified Pb(Mg1/3Nb2/3)0.65Ti0.35O3 ceramics

This work aims to study the effects of frequency on the electrical fatigue behavior of ZnO-modified Pb(Mg1/3Nb2/3)0.65Ti0.35O3 (PMNT) ceramics. Changes in microstructures, ferroelectric and piezoelectric properties of the ceramics at bipolar electrical fatigue frequencies of 5, 10, 50 and 100 Hz were observed. The thickness of damaged surface of the ceramics decreased with increasing frequency. The degradation of properties of the ceramics fatigued at low frequency was greater than those fatigued at high frequency. The degradation by electrical fatigue at lower frequencies, 5 and 10 Hz, could be caused by the effects of both field screening and domain pinning, while at higher frequencies the fatigue was mainly a result of the field screening effect. The fatigue properties of ZnO-modified PMNT ceramics was compared to Pb-based and Pb-free ferroelectric ceramics. It was found that the fatigue endurance of ZnO-modified PMNT ceramic was greater than that of hard PZT ceramic but less than that of Pb-free ferroelectric ceramic

Effects of temperature on aging degradation of soft and hard lead zirconate titanate ceramics

This paper aims to study the effects of heat treatment temperatures on the aging degradation of piezoelectric properties, i.e. piezoelectric coefficient (d33) and planar electromechanical coupling factor (kp), in soft and hard PZT ceramics. Aging degradations of d33 and kp of the samples were measured for 192 h prior to heat treatments. The samples were then treated at various temperatures equivalent to 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 times of the materials' Curie temperatures. Aging degradations of d33 and kp of the heat-treated samples were observed continuously for 1128 h. The piezoelectric properties of the un-treated samples gradually decreased with aging time. Attenuation of d33 and kp in the samples immediately after heat treatment increased with increasing heat treatment temperature. Moreover, aging degradation rate and relaxation time of the samples measured after heat treatments increased with increasing heat treatment temperature. Comparing to hard PZT ceramics, soft PZT demonstrated greater change of d33 and kp immediately after heat treatments. Soft PZT also showed greater aging rate and aging time than those of hard PZT. From the overall results, it can be concluded that both material type and heat treatment temperature have effects on aging behaviors of PZT materials. Aging degradation was more pronounced in soft PZT and the samples treated at high temperatures. The observed aging behaviors of PZT materials were explained by the interaction between domains and defects of oxygen vacancies that leads to volume, domain and grain boundary effects

CNTs-added PMNT/PDMS flexible piezoelectric nanocomposite for energy harvesting application

The flexible piezoelectric nanocomposites based on lead magnesium niobate titanate [Pb(Mg1/3Nb2/3)0.65Ti0.35O3; PMNT] particles in polydimethylsiloxane (PDMS) matrix were fabricated and characterized. PMNT powders are synthesized using the columbite precursor method. PMNT/PDMS flexible nanocomposites are then prepared by spin casting technique, where a small amount of carbon nanotubes (CNTs) is added into the PMNT/PDMS composite to enhance cross-links between PMNT particles and PDMS matrix. The phase and microstructure of the nanocomposite are investigated by using X-ray diffraction and scanning electron microscope (SEM). The electromechanical behavior is evaluated by using an autonomous pneumatic actuator. The flexible composite, occupying approximately 300 mm2, is capable of generating an open-circuit voltage (Voc) of 2.83 ± 0.24 V and a short-circuit current (Isc) signal of 0.33 ± 0.01 µA across 10 Ω resistor under mechanical load of 300 N. The generated electrical charges are 29026 pC. The relative dielectric constant is measured at 10 kHz and found to be 6.76 ± 1.15. The piezoelectric PMNT/PDMS composite can potentially be used in a variety of applications such as wearable sensors, actuators, and energy harvesting for converting kinetic energy into useful electrical energy

Dynamic processes of domain switching in lead zirconate titanate under cyclic mechanical loading by in situ neutron diffraction

The performance of ferroelectric ceramics is governed by the ability of domains to switch. A decrease in the switching ability can lead to degradation of the materials and failure of ferroelectric devices. In this work the dynamic properties of domain reorientation are studied. In situ time-of-flight neutron diffraction is used to probe the evolution of ferroelastic domain texture under mechanical cyclic loading in bulk lead zirconate titanate ceramics. The high sensitivity of neutron diffraction to lattice strain is exploited to precisely analyze the change of domain texture and strain through a full-pattern Rietveld method. These results are then used to construct a viscoelastic model, which explains the correlation between macroscopic phenomena (i.e. creep and recovered deformation) and microscopic dynamic behavior (i.e. ferroelastic switching, lattice strain).<br/

Penentuan parameter optimum bagi rawatan pengutuban elektrik ke atas seramik-piezo (BaTiO3) menggunakan sistem buatan sendiri

Kajian ini dijalankan bertujuan untuk menentukan nilai optimum bagi parameter rawatan pengutuban BaTiO3 sebagai bahan seramik-piezo dengan menggunakan sistem pengutuban DC buatan sendiri. Tiga parameter pengutuban utama yang telah dikaji adalah medan elektrik (Ep), suhu (Tp) dan masa (tp) rawatan. Fasa tunggal seramik-piezo BaTiO3 yang stabil dalam struktur hablur tetragon berjaya disediakan melalui persinteran keadaan pepejal konvensional. Pemilihan julat Ep dan Tp untuk rawatan pengutuban masing-masing adalah berdasarkan ujian awal pengukuran histeresis feroelektrik dan penentuan suhu Curie, Tc. Keputusan kajian mendapati BaTiO3 mempunyai nilai medan paksaan, Ec yang kecil (~2.42 kV/cm), pengutuban baki, Pr ~4.90 μC/cm2 dan pengutuban maksimum, Pm yang besar (~17.59 μC/cm2) dengan Tc pada 139°C. Berdasarkan julat parameter kajian, nilai pemalar piezoelektrik, d33 tertinggi ~190 pC/N diperoleh dengan magnitud medan elektrik pengutuban iaitu 1.5Ec pada suhu 60°C selama 10 min. Struktur dan morfologi BaTiO3 selepas rawatan pengutuban juga dikaji. Sistem pengutuban yang dibangunkan menyusun semula penjajaran domain secara efektif dan parameter rawatan optimum didapati setanding dengan kajian BaTiO3 lain

Orthorhombic-tetragonal phase transition induced by Ta isovalent doping and its effect on fatigue characteristics of KNL-NSTx ceramics

The effect of Ta addition on the bipolar fatigue characteristics of lead-free KNL-NSTx ceramics (x = 0, 0.04, 0.07 and 0.11 mol%) is studied. Bipolar cycling up to 1 × 106 cycles leads to strong degradation of the polarization in unmodified KNL-NS ceramics. This can be explained by the development of strong domain wall pinning, leading to the build-up of high local stresses and consequently microcracking of the material. The addition of Ta reduces the domain wall pinning effect and improves the bipolar fatigue resistance. In order to understand the fatigue mechanism, a model based on oxygen vacancy accumulation is proposed. This model is expected to guide future fatigue studies that are concerned with novel lead-free KNN-based materials

Frequency effect on electrical fatigue behaviour of lead zirconate titanate ceramics

The frequency effect on the electrical fatigue behaviour of lead zirconate titanate (PZT) ceramics for a micro-actuator of hard disk drives has been investigated. The PZT sample was subjected to a bipolar electric field of ±1 kV/mm at various frequencies; 10, 50, 100 Hz. The fatigue behaviour could be attributed to the domain pinning effect and is well quantitatively analysed by using the ferroelectric logarithmic fatigue model. Significantly, it was found that fatigue degradation is more severe at low frequency loading. The frequency effect on the fatigue behaviour was explained using the viscosity concept

Electrical fatigue-induced cracking in lead zirconate titanate piezoelectric ceramic and its influence quantitatively analyzed by refatigue method

Lead zirconate titanate (PZT) is one of the most commonly used piezoelectric ceramics. The major causes of its electrical fatigue are suggested to be domain pinning and cracking. However, their contributions to fatigue have never been quantitatively compared. This study focuses on the electrical fatigue-induced microstructure damage in the near-electrode regions of PZT and uses a refatigue method to determine quantitatively the contribution of the cracking mechanism to electrical fatigue. It is shown that during bipolar electrical cycling, a large number of cracks are initiated in the samples, and the cracking is particularly concentrated in the near-electrode regions. So the loss of piezoelectric properties can be partially restored by removing such regions. For a particular fatigue stage, the cracking mechanism contributes significantly more to the electrical fatigue than the domain pinning mechanism