Composite Eshelby model and domain band geometries of ferroelectric ceramics

A method of composite Eshelby inclusion is proposed for a ferroelectric grain with domain switching embedded in a polycrystalline ferroelectric matrix. The method quantifies the twinning structure due to spontaneous polarization, as well as the conventional and non-conventional domain structures after poling induced domain reorientation of 90 degree. The predicted parameters include the volume fraction, the thickness, and the surface inclination angle of switched domain plates. The domain wall energy for non-conventional domain structures is derived in terms of the arrays of misfit dislocations. The domain geometries predicted by the present work agree with the measured domain morphology near an indentation crack tip when subjected to lateral electric field.     

Hydrogen-induced cracking and its anisotropy of a PZT ferroelectric ceramics

The physical properties of ceramics will be degraded by charging and restored by outgassing at 650℃[1,2]. This means that atomic hydrogen can enter into ceramics through diffusion during charging. The electrical properties of the integrated PZT capacitors will be deteriorated by an-nealing in low pressure hydrogen, and the inter-layer dielectric or top electrode adhesion will be destroyed in high pressure hydrogen[3]. For an aluminum ceramics, hydrogen-induced cracking (HIC) or delayed fail…     

Sol-Gel法制备择优取向铁电陶瓷薄膜的研究进展

综述了溶胶—凝胶法制备择优取向铁电陶瓷薄膜的研究现状,主要介绍了制备过程中衬底材料、热处理工艺、前驱体以及掺杂等因素对铁电陶瓷薄膜择优取向的影响以及铁电陶瓷薄膜的择优取向与铁电性能的关系。     

Sol-Gel法制备择优取向铁电陶瓷薄膜的研究进展

综述了溶胶—凝胶法制备择优取向铁电陶瓷薄膜的研究现状,主要介绍了制备过程中衬底材料、热处理工艺、前驱体以及掺杂等因素对铁电陶瓷薄膜择优取向的影响以及铁电陶瓷薄膜的择优取向与铁电性能的关系。     

Effects of Dopants on Properties of PZN-PSN-PMN-PZT Ceramics

In order to obtain high Qm ceramics,different additives including MnO2,Fe2O3 and K2CO3 were added into the base PZT composition of xPb（Zn0.2Sn0.3Mn0.5）1/3 Nb2/3 O3-（1-x）Pb（Zr0.3Ti0.5）O3.The mechanical quality factor Qm increased while the piezoelectric constant decreased to some degree as MnO2 was added alone,Although apparent decreasing was observed in piezoelectric constanl d33 after MnO2 and Fe2O3 were added simultaneously,the mechanical quality factor Qm was kept at the same level as before,The values of d33 and Qm decreased dramatically as K2CO3 was added in combination with MnO2 and Fe2O3.The structure of grain boundary was damaged and more defects were generated by low valence K adding in this multi-impurified PZT solid.Mn doped sample presented a wide range of sintering temperatare,The properties parameters of Mn doped PZT are listed as follows;piezoelectric constant d33-256pC/N,mechanical quality factor Qm=2079,coupling coefficient Kp=0.53,Coercive field Ec=22.5kV/cm,Cure Temperature Tc=286℃.These parameters shonc that Mn-doped PZT ceramics are suitable for application in high Qm and transmitting materials.     

Microstructure and strength modification of relaxor ferroelectric ceramics through microwave sintering for multilayer capacitors

Relaxor ferroelectric ceramics with the composition of xPb( Mg_(1/3) Nb_(2/3)O_3-yPb (Zn_(1/3)Nb_(2/3)O_3-zPbTiO_3 was fast sintered in a 2.45 GHz microwave system. Microwave-sintered samples illustrate more rapid densification and much smaller grain size microstructure than eonventional sintered samples. Also the microwave processing significantly increases the dielectric strength and flexural strength of the relaxor so that its strength becomes comparable with modified BaTiO_3, and could obtain comparable dielectric properties in comparison with conventional sintering process. Microwave processing has many advantages for sintering of relaxor ferroelectrie ceramics used as multilayer capacitors.     

Fabrication of sub-micro size PZT array and their ferroelectric properties

The photosensitive PZT sols and their gel films were prepared by sol-gel process. Based on the photosensitivity of the PZT gel films, two-dimensional (2D) array of the PZT gel film was fabricated using twice-exposure of double-beam interference on the gel film. PZT gel films coated on ITO/quartz substrate were exposed to an interference fringe of 325 He-Cd laser beams, the substrate was rotated by 90° between the first and second irradiation steps. Island type periodic 2D array structures with a pitch of 1 μm and cell size of about 480 nm × 480 nm × 40 nm were formed after the irradiation, and followed by leaching with organic solvent, and then by heat treatment at 600℃ for 15 min. The hysteresis loops of the cell in PZT array were in-situ measured by the online-operation of TF analyzer and atomic force microscope (AFM). The probe can be located on the locked cell of PZT array in the AFM image. The alternating voltage applied to the locked cell is supplied by the TF analyzer through the conductive coating probe, and then the test signal is fed back to the TF analyzer to obtain the hysteresis loop of the locked cell of array in the absence of top electrode. The results show that the sub-micro size PZT arrays prepared in this way are of polarization reversal characteristics with the alternating electric fields, thereby exhibiting obvious ferroelectricity.     

薄膜厚度对铁电薄膜铁电性能的影响

为研究薄膜厚度对外延铁电薄膜铁电性能的影响,应用与时间有关的Ginzburg-Landau方程,在同时考虑应力和表面效应的条件下,获得了不同应力情况下,不同厚度铁电薄膜的电滞回线及蝶形应变迟滞回线.计算结果显示,处于不同应力值下的铁电薄膜,剩余极化强度和场致应变随着薄膜厚度的增加而增加.而矫顽场随着薄膜厚度的增加而减小.证明了不同应力情况下,薄膜厚度对剩余极化强度和矫顽场的影响是不能忽略的.这种变化趋势与实验结果的情况是一致的.     

Study on electromechanical coupling nonlinear vibration of flywheel energy storage system

The new type transforming format and storage method of electric energy have become a focus in present. With the breakthrough of high intensity fiber material, low power loss bearing, electric power and electronics technology, the attention is paid to the flywheel energy storage system (FESS) technology by domestic and overseas academia for its high efficiency of electrical energy transforming, quick charge and discharge, no pollu-tion and large energy storage density, etc. The application for…     

高强韧陶瓷的冲蚀磨损行为

本文研究了在室温、320℃、500℃等三种温度下两类陶瓷(氧化锆增韧氧化铝陶瓷,ZTA,与四方氧化锆多晶陶瓷,TZP)的冲蚀性能。ZTA陶瓷的耐冲蚀性显示出较好的温度稳定性。 SEM研究表明,具有高K_(10)的TZP陶瓷的冲蚀磨损主要由塑性变形和径向裂纹构成;ZTA陶瓷因硬度高与K_(10)值低,其冲蚀磨损主要表现为横向裂纹所引起的表面断裂。实验证明,没有常规机械性能与上述两类陶瓷的冲蚀磨损行为直接有关。     

Leakage behavior and distortion of the hysteresis loop in ferroelectric thin films

Leakage behavior and distortion of the polarization hysteresis loop in ferroelectric thin films are analyzed by applying a totally depleted asymmetric back-to-back Schottky model, with the Pt/Pb(Zr, Ti)O3/Pt ( Pt/ PZT/Pt) sandwich structural thin film capacitor as an example. Some interesting phenomena resulting from the asymmetric interfaces, such as the leakage current level, the flat-band voltage, the disclosure of the hysteresis loop, and the change in the remanent polarization and coercive field, as well as the vertical drift of the polarization hysteresis loop, are discussed in detail. The calculated results are also verified with experiments.     

机电产品再制造特性评价模型研究

为有效评估废旧机电产品的可再制造特性,支撑废旧机电产品绿色再设计和再制造方案的形成,借鉴绿色度评价的技术、质量、经济、资源、环境（TQCRE）5大决策原则,通过对影响废旧机电产品再制造的技术、经济、质量、资源、能源、时间、环境和服役性等因素进行分析,建立了废旧机电产品绿色再制造的微观评价模型、宏观评价模型和综合评价模型。     

Influence of soaking time on nonlinear electrical behavior and dielectric properties of TiO2-based varistor ceramics

The influence of soaking time on the nonlinear electrical behavior and dielectric properties of TiO₂-based varistor ceramics was investigated. Based on single sintering process, six disk samples of (Sr, Bi, Si, Ta)-doped TiO₂-based varistor ceramics were fabricated by sintering at 1 250 °C for 0.5–5.0 h. The samples were characterized by X-ray diffraction, voltage-current characteristics, energy spectra, metallographs, breakdown voltages, and apparent dielectric constant. It is found that the breakdown electrical field intensity at a current density of 10 mA/cm² decreases from 5.5 to 4.1 V/mm first and then increases to 7.0 V/mm, the nonlinear coefficient increases from 2.39 to 2.62 first and then decreases to 2.42, and the apparent dielectric constant increases from 98 200 to 115 049 first and then decreases to 73 865 with the soaking time increasing from 0.5 to 5.0 h. These indicate that the optimal soaking time is 2.0–3.0 h considering both nonlinear electrical behavior and dielectric properties.     

Effect of Pb substitution on the microstructure and ferroelectric properties of Ba<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>TiO<Subscript>3</Subscript> ceramic

Ferroelectric Ba0.7Sr0.3TiO3（BST） and partially Pb^2＋ substituted for Ba^2＋ ceramics （Ba0.7-xPbx）Sr0.3TiO3 （x=0.1-0.4, BPST） were prepared by using conventional solid-reaction method. XRD analysis shows that the samples microstructure changes from cubic phase to tetragonal one with the Pb^2＋ content increasing. ESEM analysis shows that the Pb^2＋ substituted samples have a denser and more uniform surface morphology than that of pure BST. Measured electrical properties suggest that the Pb^2＋ substitution for Ba^2＋ in the BST system enhances the ferroelectric performance obviously when x=0.2. In addition, the substitution increases the samples Curie temperature （To） r （Ba0.5Pb0.2）Sr0.3TiO3 ceramic has good ferroelectric properties measured at a maximal electric field of 30 kV/cm under the condition of room temperature. The corresponding saturated polarization （Ps）, remnant polarization （Pr） and coercive field （Ec） is respectively 15.687 μC/cm^2, 8.100 μ C/cm^2 and 6.611 kV/cm. The measured Tc of （Ba0.5Pb0.2）Sr0.3TiO3 is 117 ℃.     

精细陶瓷ATC在固相颗粒作用下的磨损行为

本工作研究了本组所开发的新型精细陶瓷ＡＴＣ的抗磨粒磨损和抗冲蚀磨损性能，与ＡＴ３０陶瓷相比，ＡＴＣ陶瓷的耐磨性较好，在磨粒磨损与大角度冲蚀磨损时更为明显，磨损表面细致，存在明显的塑性变形，磨损由单个颗粒脱落和块状脱落构成．ＡＴＣ陶瓷样品耐磨性与其强韧化水平有关．     

Dielectric,piezoelectric, and ferroelectric properties of lanthanum-modified PZTFN ceramics

Specimens of Pb1-1.5xLax（Zr0.53 Ti0.47）1-y-zFeyNb2O3 （x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01） （PZTFN） ceramics were synthesized by a semi-wet route. In the present study, the effect of La doping was investigated on the structural, microstructural, dielectric, piezoelectric, and ferroelectric properties of the ceramics. The results show that, the tetragonal （space group P4mm） and rhombohedral （space group R3c） phases are observed to coexist in the sample at x = 0.012. Microstructural investigations of all the samples reveal that La doping inhibits grain growth. Doping of La into PZTFN improves the dielectric, ferroelectric, and piezoelectric properties of the ceramics. The hys- teresis loops of all specimens exhibit nonlinear behavior. The dielectric, piezoelectric and ferroelectric properties show a maximum response atx 〉 0.012, which corresponds to the morphotropic phase boundary （MPB）.     

界面对PZT铁电薄膜性能的影响

利用射频溅射工艺,在低阻硅p-Si(111)基片上分别制备Pb(Zr0.52Ti0.48)O3(PZT)和PZT/LaN iO3(LNO)薄膜,样品在大气中进行650℃/15 min后热退火处理.用X射线衍射仪(XRD)、原子力显微镜(AFM)等手段分析不同衬底与PZT薄膜之间的界面对薄膜微观结构和铁电性能的影响,实验结果分析表明,即使溅射工艺相同,在p-Si和LNO/p-Si上外延生长的PZT薄膜结晶取向、晶颗大小和表面平整度存在很大差异,薄膜与底电极间的界面明显地影响PZT薄膜的微观结构和铁电性能.     

Transformation toughening of Al2O3/ZrO2 laminated ceramics with residual compressive stress

With the help of scanning electronic microscopy and X-ray diffraction, the relationships of microstructure characteristics, phase assemblage, and fracture micrograph of Al2O3/ZrO2 laminated ceramics were studied. Compared with monolithic Al2O3/ZrO2 ceramics, the existence of surface compressive stresses greatly restrained the growth of ZrO2 and Al2O3 grains at high sinter tem- perature, fined the grain size, and increased the content of metastable t-ZrO2, which made the fracture transformation energy quantity 70% higher than that of the monolithic ceramics. The trans-granular and inter-granular fracture features were observed in the surface and center layers, which further verified that transformation toughening is the main mechanism, whereas, micro-crack toughening is helpful for enhancing fracture toughness.     

The domain structure and polarization retention properties of PT/PZT/PT ferroelectric thin film

The highly oriented perovskite-phase PT/PZT/PT ferroelectric thin film was pre- pared by sol-gel method. The domain structures and polarization retention proper- ties were investigated by scanning force microscopy. The amplitude and phase images of piezoresponse show complex various contrasts of dark, bright and gray. The complex variation of contrast in piezoresponse images results from the per- plexing orientation of grains and arrangement of domains in the ferroelectric films. The bright and dark areas in phase images correspond to top-to-bottom and bot- tom-to-top polarization oriented c-domain, respectively. The gray areas are c-domains with the polarization vector deviating from the direction normal to the film plane. The surface potential images of EFM are bright contrast, which is due to positive charges trapped on the film surface after being polarized by positive volt- age. And the brighter contrast is obtained from the higher electric field. The time-dependent surface potential images and line potential profiles show that the potential decays with time. And the decay in the region polarized by higher electric field is faster, especially at 15 min. This indicates that the polarization retention is related to the polarized electric field. Better retention properties may be obtained from a proper polarized electric field.     

Relationship between leucite content and compressive strength of K2O-Al2O3-SiO2 system dental glass ceramics

Relationship between leucite content and compressive strength of K₂O-Al₂O₃-SiO₂ system dental glass ceramics were investigated. 10 groups of feedstock powder with different compositions were treated according to the same thermal treatment system of leucite micro-crystallization reported in some primary studies. The products of each group were analyzed by X-ray diffractometer, polaring microscope and scanning electronic microscope (SEM), and then the compressive strength was tested by a material testing machine. A direct proportion was found between leucite content and the compressive strength when leucite content was less than 50 vol%, and compressive strength decreased with the increasing of leucite micro-crystals when leucite content was more than 50vol%, The leucite content has a notable influence on the compressive strength of K₂O-Al₂O₃-SiO₂ system dental glass ceramics. Funded by the Natural Science Foundation of Hubei Province of China (No. 2006ABA250)