0．98Na0．5Bi0．5TiO3—0．02NaNbO3无铅压电陶瓷的极化研究

极化显著影响压电陶瓷的应变量和电畴转向率，从而影响其压电性能。本文研究了0．98Na0．5Bi0．5TiO3-0．02NaNbO3压电陶瓷的极化条件。研究表明极化电场为4kV／mm、极化温度为120℃、极化时间为20min时，其压电常数d33最大值为96pe·N^-1。     

多孔PZT95/5铁电陶瓷的机械性能和铁电性能研究

采用添加造孔剂的方法制备多孔锆钛酸铅(PZT95/5)铁电陶瓷, 研究了孔结构包括孔隙率、孔径及孔形状对多孔PZT95/5陶瓷机械性能和电性能的影响及机理, 并揭示多孔PZT95/5陶瓷微观结构、机械性能和铁电性能的内在联系。研究表明: 孔隙率的增加降低了多孔PZT95/5陶瓷的声阻抗, 改善了陶瓷与封装材料的声阻抗匹配. 孔隙率增加, 多孔PZT95/5陶瓷的屈服应力和剩余极化强度降低, 矫顽场强增大。孔结构对多孔PZT95/5陶瓷屈服应力的影响可由应力集中理论解释; 多孔PZT95/5陶瓷剩余极化强度随孔结构的变化可用内应力结合空间电荷理论加以解释。     

PST陶瓷的微结构和电性能研究

研究了Pb含量对PbxSr1-xTiO3（x=0．2～0．8）陶瓷微结构和介电性能的影响，当x＜0.45时，c/a≈1，晶体为立方顺电相；x≥0．45时，c/a＞1，晶体为四方铁电相；随着Pb/Sr比增大，PST陶瓷气孔率下降，致密度增加，晶粒尺寸逐渐增大，居里峰近似线性地向高温方向移动，并具有一致的居里外斯常数，剩余极化强度（Pt）、矫顽场强（Ec）都增大。     

缺陷偶极子调控铅基钙钛矿压电陶瓷性能的研究进展

压电陶瓷作为一种可以实现机械能和电能之间相互转换的功能陶瓷材料,广泛应用于传感器、制动器、超声换能器、医学超声成像及发动机燃油喷射系统等领域.在压电陶瓷中,元素掺杂可以有效调控陶瓷的电学性能,伴随掺杂而产生的缺陷偶极子对压电陶瓷性能有着显著而独特的影响.因此研究缺陷偶极子对压电陶瓷性能的调控机理,有助于理解压电陶瓷诸多物理现象的内在成因,譬如老化、疲劳等.通过元素掺杂引入的氧空位会导致钙钛矿结构的压电陶瓷产生缺陷偶极子,而缺陷偶极子与自发极化之间的耦合效应会影响陶瓷的铁电响应行为,从而使得压电陶瓷出现束腰电滞回线和偏移电滞回线等特征.另外由于陶瓷中氧空位的扩散速率很低,使得缺陷偶极子极化方向趋于稳定,进而抑制极化旋转和限制畴壁运动,有助于提高压电陶瓷的机械品质因数.尽管有大量研究通过缺陷偶极子调控压电陶瓷的宏观性能使其能够满足不同的应用需求,然而由于压电陶瓷为多晶材料,其内部晶粒取向各异且存在复杂的铁电畴结构,压电陶瓷中缺陷偶极子在形成过程中的微观机理与其具体形态以及缺陷偶极子对压电陶瓷性能的具体作用机理仍有待深入研究.此外,压电陶瓷在高驱动场下的高功率特性对机电设备的实际设计具有重要意义,因此缺陷偶极子对压电陶瓷高功率特性的影响也值得关注.本文从氧空位诱导缺陷偶极子的形成及其表征手段、缺陷偶极子对铅基压电陶瓷电滞回线的影响和不同受主掺杂对铅基压电陶瓷机械品质因数的影响出发,论述了缺陷偶极子与压电陶瓷自发极化耦合效应引发的偏移和束腰奇异电滞回线特征,揭示了缺陷偶极子主要通过抑制极化旋转和限制畴壁运动提高机械品质因数的机理.然而关于缺陷偶极子的形态、与非四方相间的耦合关系以及缺陷偶极子对压电陶瓷高功率特性的影响等问题仍需进一步的研究.     

AD95陶瓷的高压声速研究

采用VISAR技术连续测量样品-窗口界面粒子速率剖面方法,对AD95陶瓷在卸载过程中的高压声速和卸载路径进行了研究。结果表明,加载应力为25.86～57.42GPa时,AD95陶瓷卸载过程中的高压声速降低过程与延性金属材料具有明显区别:卸载过程受加载过程中的双波结构影响,明显分成弹性前驱波卸载和冲击波卸载两个阶段,但第一阶段所占的比例随加载应力的增加逐渐减小;第二阶段中不存在明显的弹性卸载和塑性卸载的拐点。研究结果将为陶瓷材料动态响应和压缩损伤研究奠定基础。     

扭转振动压电超声换能器的研究

本文对夹心式复合结构压电超声扭转振动换能器进行了系统的理论研究，该换能器由两段金属真圆棒及切向极化的压电陶瓷圆片堆复合而成，文中首先研究了切向极化压电陶瓷细长管的扭转振动性，推出了其机电等效电路，并提出了压电陶瓷细长管截面扭转系数的概念。，     

钛酸铅陶瓷的介电和极化翻转特性研究

以水热纳米粉为前驱粉料,采用传统烧结工艺在950℃制备了致密性高、具有亚微米尺寸晶粒的钛酸铅(PbTiO3)陶瓷,并对其介电温谱和压电响应特性进行了系统的研究。结果表明,PbTiO3陶瓷在低温下的相对介电常数与测试频率无关,在室温以上,随着频率的增加,介电峰值向低温方向移动;压电力显微镜研究结果显示PbTiO3陶瓷中具有明显的微区极化翻转,表明具有较好的铁电性能。     

陶瓷防隔热瓦表面难熔金属硅化物涂层的研究进展

金属硅化物因具有高熔点、高辐射及高温抗氧化性而成为高超声速飞行器陶瓷防隔热瓦表面涂层最具潜力的材料。综述了难熔金属硅化物作为大面积区域采用的陶瓷隔热瓦表面高发射率涂层材料和高温区采用的陶瓷防热瓦表面抗氧化涂层材料的研究现状,介绍了涂层制备方法的优缺点,提出了陶瓷复合材料表面涂层当前研究中存在的问题及潜在的发展方向。     

钨掺杂PZN-PZT陶瓷的结构与压电性能的研究

用二次合成法制备了掺杂WO3的PZN-PZT压电陶瓷,研究了WO3对PZN-PZT陶瓷晶胞结构与压电性能的影响,结果表明钨掺杂促进PZN-PZT陶瓷的烧结致密化,于1100℃下形成晶界清晰,结构致密的陶瓷.钨掺杂引起晶格畸变,随着钨含量的增加,晶格常数a和c减小,四方度降低;对压电性能的研究表明随着钨含量的增加,PZN-PZT陶瓷的矫顽场Ec、自发极化强度Ps、机电耦合系数Kp和压电常数d33减小,介电常数ε和机械品质因数Qm增大,绝缘电阻率ρ先增加后减小;PZN-PZT陶瓷在WO3掺杂量为1.0%(质量分数)时具有最佳综合性能.     

镧掺杂对PZN基陶瓷的电致应变和电滞后的影响

用二次合成法制备了掺镧的ＰＺＮ基多元系陶瓷并研究了镧掺杂对该体系陶瓷的相结构、介电、电致伸缩性能及电滞回线的影响。实验结果表明,随着镧含量的增加,陶瓷的钙儋 矿相含量、介电常数、同及横向电致应变和电致伸缩系数减小,电滞效应降低即剩余极化的矫场强减小,陶瓷的介电性能的温度稳定性也得到了改善。     

Inelastic response of alumina

This paper investigates the effects of microcracking, plasticity, and strain rate dependent pore closure on the inelastic deformation wave profiles of a low density (3.55 mg/m³) and a high density (3.88 mg/m³) aluminas. This is accomplished by means of numerical simulations of the measured plane shock wave profiles in these aluminas. The wave profiles were generated over a wide range of impact velocities (80 m/s to 2200 m/s). An internal-state-variable based ceramic model was used in the simulations to describe the inelastic strains due to microcracking, microplasticity, and pore collapsing. The microcrack size, number of microflaws, and limiting speed of the crack growth controlled the shape of the inelastic wave portion of the velocity profile at low velocity impact. The porosity content and the strain rate sensitivity parameter did not significantly influence the shapes of the low velocity profiles. However, these two parameters greatly influenced the profile shapes when the ceramic was shocked at high velocities well above the Hugoniot elastic limit. The simulations of high velocity experiments clearly demonstrated the need for describing the pore collapse process in order to match the measured wave profiles.     

Ultrasonic couplants for acoustic microscopy of low speed materials

A method is presented for estimating the compression wave velocities of organic fluids, based only on their density and molecular properties. The method is applied to a search for very low-speed ultrasonic couplants, suitable for 250 MHz acoustic microscopy studies of epoxy materials. Experimental measurements confirmed that acoustic velocity could be predicted within 3% for simple fluorine-containing organic compounds, and within 10% for those with a more complex molecular structure. The compound 2-dichloropentafluoropropane (C(3 )HCl(2)F(5)), with a compression wave velocity of C(L)=638 m/s and acceptably low attenuation coefficient, was identified as a good coupling agent for acoustic microscopy studies of low speed materials.     

A new point contact surface acoustic wave transducer for measurement of acoustoelastic effect of polymethylmethacrylate

A new acoustic transducer and measurement method have been developed for precise measurement of surface wave velocity. This measurement method is used to investigate the acoustoelastic effects for waves propagating on the surface of a polymethylmethacrylate (PMMA) sample. The transducer uses two miniature conical PZT elements for acoustic wave transmitter and receiver on the sample surface; hence, it can be viewed as a point- source/point-receiver transducer. Acoustic waves are excited and detected with the PZT elements, and the wave velocity can be accurately determined with a cross-correlation waveform comparison method. The transducer and its measurement method are particularly sensitive and accurate in determining small changes in wave velocity; therefore, they are applied to the measurement of acoustoelastic effects in PMMA materials. Both the surface skimming longitudinal wave and Rayleigh surface wave can be simultaneously excited and measured. With a uniaxial-loaded PMMA sample, both acoustoelastic effects for surface skimming longitudinal wave and Rayleigh waves of PMMA are measured. The acoustoelastic coefficients for both types of surface wave motions are simultaneously determined. The transducer and its measurement method provide a practical way for measuring surface stresses nondestructively.     

PZT铁电陶瓷及其在脉冲能源中的应用

以PZT 95/5陶瓷为例,概述了铁电陶瓷在脉冲能源上的应用及材料对能源性能的影响.主要包括陶瓷的制备及性能、陶瓷的冲击放电机理和陶瓷的冲击放电效应及影响因素.通过比较我们认为,陶瓷的研制,特别是密度的改变对陶瓷的力学及电学性能影响较大.陶瓷冲击加载下的新应用,将带动陶瓷各方面性能的深入研究.     

PZT/环氧树脂1-3-2型压电复合材料的制备及性能

采用压电陶瓷基板与1-3型压电复合材料串联连接,沿表面两相互垂直的方向切割PZT陶瓷,在切槽间浇注环氧树脂,制备出新型的1-3-2型压电复合材料.实验测试了材料的压电和介电性能,结果表明其d33常数达到400 pC/N,振动位移113.5pm,声速3500m/s,声阻抗17.6Mraly,厚度机电耦合系数0.62,带宽3.6kHz,相对介电常数817,介质损耗0.02.     

Acoustic microscopy measurement of elastic constants and massdensity

A method is presented to determine the elastic constants and the mass density of isotropic and anisotropic solids and anisotropic thin films. The velocity and attenuation of leaky surface acoustic waves (SAWs) have been obtained for specified propagation directions from V(z) curves measured by line-focus acoustic microscopy (LFAM). The experimentally obtained velocities have been compared to velocities obtained from a measurement model for the V(z) curve which simulates the experiment. Since the measured and simulated V(z) curves have the same systemic errors, the material constants are free of such errors. For an isotropic solid, Young's modulus E, the shear modulus G and the mass density ρ have been determined from the leaky Rayleigh wave velocity and attenuation, measured by LFAM, and a longitudinal wave velocity measured by a pulse-echo transit-time technique. For a cubic-crystalline solid, the ratios of the elastic constants to the mass density (c₁₁ /ρ, c₁₂/ρ, c₄₄/ρ) have been determined from the directional variation of measured SAW velocities, using a preliminary estimate of ρ. The mass density ρ has subsequently been determined by additionally using the attenuation of leaky SAWs in crystal symmetry directions. For a cubic-crystalline thin film deposited on a substrate, the elastic constants and the mass density (c₁₁, c₁₂, c₄₄, ρ) of the film have been determined from the directional variation of the measured SAW velocities, and a comparison of the corresponding attenuation coefficient with the measured attenuation coefficient has been used to verify the results     

Characterization of the alumina–zirconia ceramic system by ultrasonic velocity measurements

In this work an alumina–zirconia ceramic composites have been prepared with α-Al₂O₃ contents from 10 to 95 wt.%. The alumina–zirconia ceramic system was characterized by means of precise ultrasonic velocity measurements. In order to find out the factors affecting the variation in wave velocity, the ceramic composite have been examined by X-ray diffraction (XRD) and (SEM) scanning electron microscopy. It was found that the ultrasonic velocity measurements changed considerably with respect to the ceramic composite composition. In particular, we studied the behavior of the physical material property hardness, an important parameter of the ceramic composite mechanical properties, with respect to the variation in the longitudinal and shear wave velocities. Shear wave velocities exhibited a stronger interaction with microstructural and sub-structural features as compared to that of longitudinal waves. In particular, this phenomena was observed for the highest α-Al₂O₃ content composite. Interestingly, an excellent correlation between ultrasonic velocity measurements and ceramic composite hardness was observed.     

LiNbO3和LiTaO3晶体电子结构、平面声波和光折射特性

本研究基于密度泛函理论的第一性原理超软赝势平面方法计算了LiNbO₃和LiTaO₃的晶格参数、电子结构和弹性常数, 并利用Christoffel方程研究了二者平面声波特征。结果表明: 两者的理论计算晶格参数和弹性常数与实验值接近, 禁带宽度分别为3.78和3.98 eV, 导带底和价带顶主要由O-2p和Nb-4d(Ta-5d)态电子贡献。化学键理论揭示Li和Nb(Ta)与O原子之间有两种成键类型。 电荷布局分析结果显示有两种相应的重叠布居数, Nb(Ta)-O键呈现强共价键作用, 并且Nb-O(Ta-O)键长小于Li-O键长。LiNbO₃和LiTaO₃晶体平面声波有两支横波和一支纵波, 纵波速度大于横波速度, 在xy平面呈现六重对称性, 在xz和yz平面各向异性程度强于xy平面, 沿[001]、晶向上两支横波振动速度相等。最后利用模守恒赝势(Norm-conserving)计算了介电常数和静态折射率, 计算表明LiNbO₃晶体的折射性能和非寻常光(e光)离散程度均强于LiTaO₃晶体。     

High-accuracy standard specimens for the line-focus-beam ultrasonic material characterization system

We prepared standard specimens for the line-focus-beam ultrasonic material characterization system to obtain absolute values of the propagation characteristics (phase velocity and attenuation) of leaky surface acoustic waves (LSAWs). The characterization system is very useful for evaluating and analyzing specimen surfaces. The calibration accuracy of these acoustic parameters depends on the accuracy of acoustical physical constants (elastic constants, piezoelectric constants, dielectric constants, and density) determined for standard specimens. In this paper, we developed substrates of non piezoelectric single crystals (viz., gadolinium gallium garnet [GGG], Si, and Ge) and an isotropic solid (synthetic silica [SiO₂] glass) as standard specimens. These specimens can cover the phase velocity range of 2600 to 5100 m/s for Rayleigh-type LSAWs. To determine the elastic constants with high accuracy, we measured velocities by the complex-mode measurement method and corrected diffraction effects. Measurements of bulk acoustic properties (bulk wave velocity and density) were conducted around 23°C, and bulk wave velocities were obtained with an accuracy of within ±0.004%. We clearly detected differences in acoustic properties by comparing the obtained results with the previously published values; the differences were considered to be due to differences of the specimens used. We also detected differences in acoustic properties among four SiO₂ substrates produced by different manufacturers     

高活性锆钛酸铅压电陶瓷粉体的合成及其烧结性能研究

以Pb3O4、ZrO2和TiO2为原料,采用冲击波加载技术合成锆钛酸铅Pb(Zr0.95Ti0.05)O3粉体,并对粉体活性和烧结特性进行XRD和SEM表征,研究结果表明,利用冲击波的高温高压作用可以合成单一钙钛矿相锆钛酸铅粉体,合成粉体产生了细化并存在一定程度的晶格畸变,有利于增强粉体活性,促进了低温活化烧结,也显著地改善了陶瓷的烧结性能,在常压下1200℃烧结150min得到了密度达到7.83g/cm3的锆钛酸铅95/5陶瓷体,比传统固相法制备的粉体烧结温度降低了100℃左右,且得到的陶瓷体晶粒形状、大小均匀。