High piezoelectricity of low-temperature sintered Li2CO3-added PNN–PZT relaxor ferroelectrics

Journal of Materials Science: Materials in Electronics - High piezoelectric properties (d33?=?936 pC/N, d33*?=?1015 pm/V, and kp?=?0.701) are obtained...     

PNN／PZT系梯度功能压电陶瓷离子互扩散动力学

研究了ＰＮＮ／ＰＺＴ系梯度功能压电材料中各类离子互扩散反应及其随温度和时间的变化。用电子探针测量了互扩散偶的组分分布，利用“薄板叠加”扩散模型，对Ｎｉ＾２＋、Ｎｂ＾５＋，Ｔｉ＾４＋和Ｚｒ＾４＋的扩散浓度分布曲线进行数值逼近计算，确定了互扩散层的厚度，估算了各离子的扩散系数及其表现激活能。     

PNN/PZT系梯度功能压电材料的离子互扩散

本文研究了PNN／PZT系梯度功能压电材料中,不同离子（Nb⁵⁺、Ni²⁺、Zr⁴⁺、Ti⁴⁺）的互扩散反应随扩散温度和扩散时间的变化规律．利用电子探计（EPMA）测量了离子的组份分布,确定了离子互扩散层的厚度．采用“薄板扩散叠加”模型,对Ni²⁺、Nb⁵⁺、Ti⁴⁺和Zr⁴⁺离子的组份分布进行了计算机数值模拟,结果与EPMA实验相吻合．估算了离子的扩散系数与表观激活能,并对此进行了讨论．     

The effect of acid mixture on the structure of sol–gel PZT fibers

Author's previous studies [J. Am. Ceram. Soc., in press] showed that the acidification of the precursor solution controls the strength and length of sol–gel PZT fibers. Two acids, acetic acid (CH₃COOH) and methacrylic acid (C₄H₆O₂), were studied. C₄H₆O₂ produced longer fibers with small cracks, while CH₃COOH produced shorter and denser fibers. In order to take advantage of the opposite effect of each of these acids, mixtures of acetic and methacrylic acid are used in this work to obtain longer and dense fibers. The effect of the ratio of CH₃COOH/C₄H₆O₂ mixture on the precursors' chemical structure, crystalline phase formation and microstructure of PZT fibers is investigated and discussed. Long and almost crack-free PZT fibers are obtained for a 1/2 ratio of CH₃COOH/C₄H₆O₂.     

Processing and properties of 15–70 MHz 1–3 PZT fiber/polymer composites

This paper reports on the fabrication and characterization of fine scale piezoelectric composites with 1–3 connectivity using fibers derived from a metal alkoxide sol-gel process. Using this technique, pure thickness mode resonance for this type of composite has been increased from 15 MHz up to 70 MHz by maintaining pillar aspect ratio requirements. Piezoceramic fibers of Nb or La modified lead zirconate titanate (PZT) were produced with final diameters ranging from 15 to 50 μm. Composites having 1–3 connectivity were produced using the fibers as pillars. Composites could be fabricated with volume fractions from 10 to 45% allowing tailoring of both the dielectric constant and acoustic impedance without degrading coupling. Dielectric constant, polarization and coercive field values varied slightly from bulk values due to clamping by the polymer matrix, increasing as the fiber diameter decreased. Composites with resonance frequencies ranging from 15 to 70 MHz were studied. The thickness dependence of the properties gave indications to radial mode/thickness mode interactions at pillar aspect ratios near 1.7 to 1 thickness to diameter. Coupling coefficients (k_t) from 58% to 73% with mechanical quality factors <15 were detected. Received: 4 April 2000 / Reviewed and accepted: 8 June 2000     

Fabrication and properties of an anisotropic PZT/polymer 0–3 composite

Anisotropic 0–3 PZT platelet/polymer composites were prepared by a route involving the tape casting and sintering of PZT sheets and the subsequent alignment of platelets in a polymer matrix by either calendering or tape casting; both techniques induced a strong alignment of the platelets. At 60 vol 1/2 loading, measured d ₃₃- and d _h-values of ~ 30 pC N^–1 and ~ 100 pC N^–1, respectively, were obtained; the calculated g _h-value was 83 mV mN^–1. A strong relaxation effect observed is considered most likely to be dependent on the characteristics of the polymer phase.     

Peculiarities of the Structure and Properties of Thin PZT Films with Strongly Nonuniform Depth–Composition Profiles

Technical Physics Letters - Two-layer thin films of lead zirconate titanate (PZT) with lead content in the layers differing by 20% were deposited by RF magnetron sputtering at variable working gas...     

Enhanced electrical properties of PZT thick films prepared by sol–gel technique through step-by-step crystallization process

[Pb(Zr_xTi_1-x)O₃: PZT] films at morphotropic phase boundary composition (x = 0.52) were deposited on bare Si, ZrO₂/Si and Pt/Ti/SiO₂/Si substrates by sol–gel spin on technique. Films deposited on the bare Si and ZrO₂/Si substrates had low degree of crystallization and micro cracks. Well crystallized films with smooth microstructure were obtained on Pt/Ti/SiO₂/Si substrates. Further, the thickness of the films on Pt/Ti/SiO₂/Si substrate was increased up to ~1 μm by step-by-step crystallization process. The single perovskite phase of the above films was confirmed with X-ray diffraction analysis. Films had enhanced dielectric properties at room temperature and the dielectric constant values were comparable to those of bulk values at Curie temperature (T_c) from the temperature dependent dielectric measurements. Films exhibit higher remnant polarization (P_r) and lower coercive field (E_c) values. Further, capacitance–voltage (C–V), current–voltage (I–V) measurements and rough estimation of piezoelectric coefficient of the films were carried out.     

Synthesis and crystallization of lead–zirconium–titanate (PZT) nanotubes at the low temperature using carbon nanotubes (CNTs) as sacrificial templates

Pb(Zr_0.52Ti_0.48)O₃ (PZT) nanotubes with diameters of 80–100 nm and a wall thickness of 15–20 nm were prepared by sol–gel template technique and using multi-walled carbon nanotubes (MWCNT) as sacrificial templates. The coating process of MWCNT with PZT precursor sol and removal of the carbon nanotubes by an interrupt heat treatment were discussed and studied by Raman spectroscopy. Simultaneous thermal analysis (STA) revealed that PZT nanotube crystallized at the low temperature of 410 °C by the significantly low activation energy of crystallization of 103.7 kJ/mol. Moreover, based on the X-ray diffraction (XRD) pattern and selected area electron diffraction pattern the crystal structure of the PZT nanotube was determined as perovskite. High resolution transmission electron microscope (HRTEM) and field-emission scanning electron microscope (FE-SEM) images proved that the final PZT had a tubular structure.     

Investigation of mechanical properties of advanced Al–Zn–Mg–Cu alloy

Abstract

The mechanical properties of the rapidly solidified 7000 series powder alloy CW 67 were investigated for various extrusion and heat treatment conditions. The principal aim of the work was to ascertain the optimum processing route for peak aged (T6) material. The highest proof stress in the T6 condition was found to be 572 MN m^?2 for material extruded at 325°C and aged for 13·5 h at 120°C after solutionising. The ductility of this material was found to be 13·5%. The fracture toughness was measured in two orientations and found to be approximately 21 MN m^?3/2 in the short transverse direction and 44 MN m^?3/2 in the longitudinal direction. Degassing and hot compaction was found to improve the fracture toughness of the material substantially.

MST/1504     

PZT含量对PZT/PVDF复合材料性能的影响

采用流延工艺,在ITO玻璃衬底上制备了不同质量分数的锆钛酸铅(PZT)/聚偏氟乙烯(PVDF)热释电复合材料。采用X射线衍射方法对复合材料极化前后的物相变化进行了对比分析,通过扫描电子显微镜分析了不同PZT质量分数复合材料的界面特征。从热释电探测器件的实际要求出发,利用介电阻抗测试仪、动态法热释电系数测试系统等仪器系统地测试了复合材料体系中PZT含量对材料热释电性能和介电性能的影响。结果显示,在PZT质量分数为50%时,制得了热释电系数p为4.1nC/(cm2.K)的性能优良的热释电复合材料。     

Extrusion of AI–Zn–Mg–Cu–Zr alloys

Abstract

Four aluminium alloys of different zinc/magnesium ratio have been studied under various extrusion conditions. The alloys were cast in steel book moulds and subjected to initial thermomechanical treatments. Studies were made of hot extrusions and cold hydrostatic extrusions and in each case the changes in the extrusion parameters were analysed. An attempt has been made to explain some of the extrusion defects which appeared in various extruded sections. The extrusion speed was found to be crucial, since sections developed surface cracks at higher speeds. The extrusion speed was also found to vary inversely with the extrusion ratio, with higher speeds at low ratios. A well defined solute–depleted weld zone was observed on each of the four faces of a square tube extruded using a porthole die. Thermal treatment was not found to improve this weak weld zone. Tubes extruded using a floating-mandrel die withstood pressure testing up to 550 MPa.

MST/43     

The Effect of Sn Substitution of Pb on Microstructure and Superconducting Properties of Bi–Pb–Sr–Ca–Cu–O Superconductor

The effect of substitution of Pb by Sn in Bi_1.6Pb_0.4?x Sn _x Sr₂Ca₂Cu₃ O _δ samples at x = 0.0, 0.1, 0.2, and 0.3 on the critical transition temperature and structural properties was investigated in this work. All the samples were prepared by the solid-state reaction method. The prepared samples were characterized by X-ray diffraction (XRD), resistance–temperature curve (R–T), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The Sn ⁴⁺ substitution of Pb ²⁺ caused significant changes in the properties of the samples. The formation of the (Bi, Pb)-2212 phase was stabilized and the T _c (onset) was improved at the x = 0.2 level of Sn ⁴⁺ substitution. The SEM micrographs have shown that the structure of the sample with x = 0.2 became more dense. However, samples with x = 0.1 and 0.3 have not shown zero resistance by EDS analysis because of oxygen deficiency.     

Application of time–temperature–stress superposition on creep of wood–plastic composites

Time–temperature–stress superposition principle (TTSSP) was widely applied in studies of viscoelastic properties of materials. It involves shifting curves at various conditions to construct master curves. To extend the application of this principle, a temperature–stress hybrid shift factor and a modified Williams–Landel–Ferry (WLF) equation that incorporated variables of stress and temperature for the shift factor fitting were studied. A wood–plastic composite (WPC) was selected as the test subject to conduct a series of short-term creep tests. The results indicate that the WPC were rheologically simple materials and merely a horizontal shift was needed for the time–temperature superposition, whereas vertical shifting would be needed for time–stress superposition. The shift factor was independent of the stress for horizontal shifts in time–temperature superposition. In addition, the temperature- and stress-shift factors used to construct master curves were well fitted with the WLF equation. Furthermore, the parameters of the modified WLF equation were also successfully calibrated. The application of this method and equation can be extended to curve shifting that involves the effects of both temperature and stress simultaneously.     

Influence of ageing on wear resistance of an Fe–Mn–Si–Cr–Ni–Ti–C shape memory alloy

To further improve the wear resistance of Fe–Mn–Si–Cr–Ni based shape memory alloys, the effects of ageing at 1123 K with and without pre-deformation at room temperature on the precipitation of second-phase particles and their effects on wear resistance were investigated in an Fe–Mn–Si–Cr–Ni–Ti–C alloy. Results showed that the solution treated Fe–Mn–Si–Cr–Ni–Ti–C alloy exhibited much better wear resistance than the solution treated AISI 321 stainless steel; ageing with pre-deformation improved the wear resistance of Fe–Mn–Si–Cr–Ni–Ti–C alloy more effectively than ageing without pre-deformation, especially under the heavy load condition.     

Constitution of Ti–Al–Ru system

Abstract

The constitution of the Ti–Al–Ru system has been studied in detail. Metallography, X-ray diffraction, electron microscopy, and X-ray spectroscopy have been used to establish the phase diagram between 17 and 37 at.-%Al and 1 and 29 at.-%Ru in the temperature range 1250–770°C. Ternary isothermal sections within the range of investigation and selected phase composition data are presented and phase relationships are discussed. Results show only a small solubility (< 1at.-%) of ruthenium in Ti₃Al and TiAl which are involved in equilibria with a ternary intermetallic compound.

MST/963     

Ferroelectric hysteresis and improved fatigue of PZT (53/47) films fabricated by a simplified sol–gel acetic-acid route

Double-layer Pb(Zr_0.53Ti_0.47)O₃ films were fabricated by spin coating of a sol–gel acetic-acid-based precursor solution deposited onto commercial Pt–Si substrates. The structural properties of the samples were studied by several diffraction, spectroscopy and microscopy techniques. The annealed ferroelectric films were crystallized to a pure PZT perovskite phase. A significant monoclinic phase content was found together with a relatively large tetragonal c/a ratio, according to the diffraction pattern refinement results. No traces of organic material were observed. Good film densification with relatively large grain sizes and low surface roughness was achieved. Ferroelectric domain distribution and local piezoresponse hysteresis loops were investigated by piezoresponse force microscopy. The films showed good local ferroelectric properties and a relatively large d₃₃ piezoelectric coefficient was derived. A degree of self-polarization of the film was also found from the domain distribution-map analysis. Good macroscopic ferroelectric properties were also achieved, specially for the film with less rhombohedral content. An improved ferroelectric fatigue behavior was observed as the films proved to sustain down to 10⁸ fatigue cycles with only a 10 % decrease of the initial remnant polarization.     

Effect of CeLa addition on the mechanical properties of Al–Cu–Mn–Mg–Fe alloy

The rapid development of new energy automobiles leads to an increasing demand for high-strength lithium battery shell alloy. The microstructures, electrical conductivity and mechanical properties of CeLa-containing Al–Cu–Mn–Mg–Fe alloys were investigated with scanning electron microscopy (SEM), X-ray diffraction, Eddy Current conductivity tester, tensile testing and Erichsen cup testing. Experiment results indicate that Al₆(Mn, Fe) particles could be refined by CeLa alloying and AlCuCeLa phase nucleates and grew up at the surface of Al₆(Mn, Fe) particle. Major texture of the CeLa-containing alloys was different from that of the CeLa-free alloy. The electrical conductivity decreased with increase of the CeLa content. CeLa addition could greatly enhance the tensile strength of the alloy at temperatures ranging from –40°C to 300°C.     

Effect of Homogenization Process on Microstructure of Al–Zn–Mg–Cu Aluminum Alloys

Herein, the best homogenization process of 466.5 °C × 36 h + 490 °C × (14–26.4 h) that can completely eliminate the coarse phases σ[Mg(Zn, Al, Cu)₂] and S(Al₂CuMg) in the Al–Zn–Mg–Cu aluminum alloy is developed. The homogenization process is determined by the method of calculation phase diagram, and the experimental verification. It is shown in the results that, first, in the microstructure of the as-cast alloys, the crystal structure of the σ[Mg(Zn, Al, Cu)₂], Al₇Cu₂Fe, and Mg₂Si phases is determined. Second, during the homogenization process, the σ[Mg(Zn, Al, Cu)₂] phase dissolves and also transforms into the S(Al₂CuMg) phase. Most importantly, the dissolution temperature range of the σ[Mg(Zn, Al, Cu)₂], S(Al₂CuMg), and Al₇Cu₂Fe phases is determined from 472.56 to 476.36 °C, from 484.09 to 485.39 °C, and from 540.18 to 547.23 °C, respectively. At best homogenization process, the residual Al₇Cu₂Fe phase area fraction ranges from 1.28 ± 0.16% to 1.60 ± 0.18%. In addition, dispersed η(MgZn₂) phase precipitates in supersaturated Al-matrix during differential scanning calorimeter heating. And, the concentration differences between the grain center and the eutectic of structure of Zn, Mg and Cu regression equations are established, which can provide some reference for the design of experimental parameters, thus reducing the experimental workload.