压电陶瓷

Electrorheological 电流变电流变液 (Electrorheological Fluids)是一种智能流体，通常是由高介电常数的微米量级颗粒分散于低介电常数的绝缘油中而形成的悬浮液。

microfluids 微流体Mechanisms 机制，机械Dynamics 动力，动力学Induced polarization 感应激发极化rheological 流变学的，液流学的effective dielectric constant 有效介电常数insulating 绝缘的在他们研发后的近六十年时间里，电流变液体已经成为具有日益增长的科研魅力和实践重要性的材料。

这个评论追溯到机械装置，是由于这些液体的电流变反应和他们伴随的理论基础。

尤其是，电流变液体被分为了两个不同类型，非传导性的电流变和PZT（锆钛酸铅）piezoelectric ceramic transducer是PbZrO3和PbTiO3的固溶体，具有钙钛矿型结构。

PbTiO3和PbZrO3是铁电体和反铁电体的典型代表，因为Zr和Ti属于同一副族，PbTiO3和PbZrO3具有相似的空间点阵形式，但两者的宏观特性却有很大的差异，钛酸铅为铁电体，其居里温度为492℃，而锆酸铅却是反铁电体，居里温度为232℃，如此大的差异引起了人们的广泛关注。

研究PbTiO3和PbZrO3的固溶体后发现PZT具有比其它铁电体更优良的压电和介电性能，PZT以及掺杂的PZT系列铁电陶瓷成为近些年研究的焦点PZT压电陶瓷是将二氧化铅、锆酸铅、钛酸铅在1200度高温下烧结而成的多晶体。

具有正压电效应和负压电效应。

具有体积小，重量轻，精度和分辨率高，频率高，出力大等优点目前从环境保护的角度来讲，PZT已经被禁用了现代压电陶瓷材料正在向着复合化，薄膜化，无铅化和纳米化方向发展压电陶瓷在人们生活中的很多方面具有重要的应用，但是目前全球在大量使用的压电陶瓷材料仍是传统的含铅压电陶瓷，其中铅元素高达60%以上。

氧化铅是一种易挥发的有毒物质，在生产，制备，使用，和废弃后的处理过程中，都给人类和生存环境造成损害。

随着环保意识的日益深入，国际上正积极通过法律、法规、政府指令等形式对铅的的电子产品加以禁止。

高温烧结时氧化铅的挥发，在对环境造成污染的同时，还会造成陶瓷化学计量比的偏离，影响材料性能。

因此，无铅压电陶瓷逐渐成为压电陶瓷研究的热点之一。

无铅压电陶瓷的种类主要有：BaTiO3基无铅压电陶瓷、铌酸盐基无铅压电陶瓷、铋层状结构无铅压电陶瓷和BNT 基无铅压电陶瓷等WHAT IS “PZT”?PZT, or lead zirconate titanate (Pb[Zr(x)Ti(1-x)]O3), is one of the world’s most widely used piezoelectric ceramic materials. When fired, PZT has a perovskite （钙钛矿）crystal structure（晶体结构）, each unit of which consists of a small tetravalent （四价的）metal ion(离子) in a lattice（晶格）of large divalent（二价金属）metal ions. In the case of （至于，在。

的情况下）PZT, the small tetravalent metal ion is usually titanium（钛）or zirconium（锆）. The large divalent metal ion is usually lead（铅）. Under conditions that confer a tetragonal or rhombohedral symmetry on the PZT crystals （鉴于压电陶瓷晶体拥有一个正方体或者斜方六面体的对称性的情况下）, each crystal has a dipole moment（电偶极矩）.PZT materials, and piezoelectric materials more generally, exhibit a unique range of properties（特殊的性能排列）. In a basic sense, if a piezoelectric material is deformed（变形畸形的）, an electric charge is generated in what is known as the piezoelectric effec（由于压电效应会产生电荷）t. The opposite of this phenomenon also holds true（相反同样有效）: If an electric field（电场）is applied to a piezoelectric material, deformation occurs in what is known as the inverse（相反的颠倒的）piezoelectric effect.PZT is a metallic oxide（金属氧化物）based piezoelectric material developed by scientists at the Tokyo Institute of Technology（东京理工学院）around 1952.（PZT是在大约1952年东京理工学院研发的压电材料基础之上的一中金属氧化物）In comparison to the previously discovered metallic oxide based piezoelectric material Barium Titanate （钛酸钡）(BaTiO3), PZT materials exhibit greater sensitivity （灵敏度）and have a higher operating temperature（工作温度）.PZT materials supplied by APC International are manufactured from high purity（高纯度的）precursors （先驱者，前体细胞）, with properties（属性）optimized for specific applications by adjusting the zirconia:titania（二氧化钛）ration, and/or by including secondary materials.How is PZT Manufactured?Figure1: The process of manufacturing PZT powders（散剂，粉剂）consists of six distinct（不同的）unit operations （化工单元操作）(See Figure 1). High-purity raw（原材料）materials are evaluated, selected and sourced（获得）throughout the world. Selection criteria, in addition to（除了。

之外）purity, include material activity（活力）and limits on specific deleterious impurities（有毒杂质）.Once each material is selected and approved for use, it is precisely weighed（精确的称重）, according to the formulation being manufactured（加工配方）, and transferred to wet mills（湿磨机）. These ingredients（原料）are wet-milled（铣削）together in their proper proportions（适当比例）to achieve a uniform particle size distribution（粒度分布）. Precise control over particle size distribution is necessary to ensure appropriate material（适合材质）activity during the calcination（煅烧）.Following the wet milling process, the product is dried（干的）and prepared for calcining（煅烧）. The product must be calcined in high-purity crucibles（坩埚）to guarantee no chemical contaminants（污染物）are present in the final product. The calcining operation is carried out（进行发生）in air at about 1000°C, where the desired PZT phase（所需的压电陶瓷相）is formed.It is important to remember that the major ingredient（成分）in PZT material is lead oxide（氧化铅）, which is a hazardous materia（危险物）l with a relatively high vapor pressure（蒸汽压）at calcining temperatures. Therefore, it is possible to alter the desired composition by allowing too much lead （铅）to evaporate（使蒸发）during the firing operations（烧制）. Proprietary measures（独特）are employed to ensure lead loss is not a factor.After calcining, the PZT powder is returned to the mill （磨坊）to ensure homogeneity（同质性均匀性）and to prepare the material for the addition of an organic binding agent（有机粘合剂）. Thebinder-containing slurry（密封的粘合剂的研磨液）is then fed to（供应给）a spray dryer（喷雾干燥机）, where water is evaporated. A successful spray drying operation requires experienced operators who can regulate the temperatures within the unit in accordance with the solids content（固体含量）of the slurry material, as well as the volume of slurry entering the dryer.The purpose of spray drying the PZT powder material（粉状材料）is to provide a free-flowing（自由流畅的）product in the form of（以某种形式）binder-containing（粘合密闭型的）hollow spheres（空心球体）with a narrow（紧凑的）particle size distribution（粒度分布）. The morphology（形态学）of the PZT material is crucial to consistently fill die cavitie（刚模穴，阴模）s in the dry pressing（干压成型）process when manufacturing piezoelectric ceramics. The uniform PZT spheres of appropriate particle size distribution（压电陶瓷球的均匀适当的粒度分布）allow for air escapement（空气擒纵机构）throughout the compaction（压实）process, yielding lamination-free（免层压）green ceramic shapes.What is PZT made of?PZT was developed around 1952 at the Tokyo Institute of Technology. PZT is composed of the two chemical elements lead and zirconium combined with the chemical compound titanate(钛酸盐的化合物). PZT is formed（成形）under extremely high temperatures. The particulates（悬浮颗粒）are filtered out(过滤掉) using a mechanical filter.（机械过滤器）Popularity of PZT CeramicPZT, lead zirconate titanate（锆钛酸铅）, is the most commonly used piezo ceramic today. In general, piezo ceramics are the preferred choice because they are physically strong（物理结构上的牢固）, chemically inert（化学惰性）and relatively inexpensive to manufacture. Plus（再者）, they can be easily tailored（定做）to meet the requirements of a specific purpose. PZT ceramic is revered（拥戴）because it has an even greater sensitivity（高度灵敏）and higher operating temperature than other piezo ceramics.PZT Ceramic ApplicationsPZT ceramic is used in a wide variety of applications. Soft (sensor) PZT ceramic（柔软的pzt陶瓷）powders are typically used when high coupling （高度耦合）and/or high charge sensitivity （高电荷灵敏度）are important, such as in flow（流体）or level sensors（液面传感器）; ultrasonic nondestructive testing（超声波的无伤测试/评估的应用）/evaluation (NDT/NDE) applications; or for accurate inspections of automotive, structural or aerospace （汽车，建筑，航天工具）products. Material characteristics include a high dielectric constant（高介电常数）; high coupling（高度耦合）; high charge sensitivity; high density（高密度）with a fine grain（微利）structure; a high Curie point（居里温度）; and a clean, noise-free frequency response（频率响应）.Hard (high power（大功率）) PZT ceramic powders are used when high power characteristics are required, including applications such as the generation of ultrasonic or high-voltage（高电压）energy in ultrasonic cleaners（超声波清洗机）, sonar devices, etc. Important powder characteristics include a high piezoelectric charge constant (d33); a higher mechanical quality factor（品质因素）that reduces mechanical loss（机械损失）and enables a lower operating temperature; a low dissipation factor（损耗因数）that ensures cooler, more economical operation; high dielectric stability（电解质的稳定性）; and low mechanical loss under demanding conditions（需求状况）.作为PZT材料的一个基本组成成分PbTiO3，虽被发现甚早，但由于其烧结困难等制作工艺等原因，长期内不能实际应用。