微孔结构氟聚合物铁电驻极体的制备及其热稳定性研究

描述了一种微孔结构氟聚合物铁电驻极体的制备方法，利用准静态方法测量了该功能膜的压电系数如，并通过等温衰减和热刺激放电电流谱的测量研究了凼，的热稳定性。结果表明，这类氟聚合物铁电驻极体膜的准静态压电系数d33与热压时间有关；与聚丙烯（PP）压电驻极体膜相比较，氟聚合物压电驻极体膜不但具有更高的压电活性，而且呈现更优良的热稳定性。     

聚丙烯孔洞型铁电驻极体薄膜的压电性研究

利用准静态法和激光干涉法测量正、逆压电d33系数,研究了经压力膨化处理的聚丙烯孔洞型铁电驻极体薄膜压电系数的压强和频率特性及其热稳定性.结果表明,聚丙烯薄膜经压力膨化处理后,其压电性能改善的原因是:压力膨化处理既能有效地降低孔洞膜的弹性模量Y,又能增强其储电能力.聚丙烯孔洞膜的压电d33系数在激励信号压强为0.2～4kPa的范围内基本保持恒定,但当其值高于4kPa时,d33系数出现了明显的下降.聚丙烯孔洞膜的压电d33系数随频率上升而下降(即从0.001Hz时的1200pC/N降低到其机械共振频率附近时的350pC/N),是与材料的弹性模量Y随频率的上升而增加直接相关.对不同工艺参数制备的样品,其机械共振频率位于150～400kHz范围内.实验结果还表明:聚丙烯孔洞膜的压电d33系数的热稳定性与非孔洞型聚丙烯驻极体薄膜的电荷储存热稳定性相近.     

经二次膨化工艺优化的孔洞结构聚丙烯薄膜的压电性

报道了提高孔洞结构压电驻极体膜压电活性的新方法。该方法是在对已膨化处理的压电驻极体薄膜再进行一次膨化处理,通过调节薄膜的力学性能来进一步优化材料的压电活性。结果表明,将聚丙烯（PP）压电驻极体薄膜进行二次膨化处理后,其压电活性比一次膨化的PP薄膜提高约40％。这是因为薄膜在真空蒸镀电极过程中导致的厚度减小能够通过二次膨化工艺得到恢复,而厚度的增加可以有效地降低材料的杨氏模量,从而使薄膜的压电系数d33增加;两次膨化温度对压电系数d33均有影响,并且相互联系;通过选择合理的一次和二次膨化工艺参数（例如100℃和45℃）能够获得稳定的高压电系数压电驻极体膜。     

微结构PDMS压电俘能器设计与特性研究

设计了一种具有三明治结构的微结构驻极体膜,采用旋涂、"软刻蚀"等工艺,结合氧等离子体键合、恒压电晕放电技术,以铜网作为电极,摸索出完整的工艺流程,制作了基于微结构PDMS驻极体的柔性压电俘能器。测量了驻极体膜的压电系数以及力-电特性。结果显示,微结构PDMS压电俘能器的压电系数(d33)为25pC/N;在5N周期性压力下,最大能够产生1.98Vpp的开路电压;驻极体膜的谐振频率为32Hz,且产生的电压与受到的压力呈线性关系。     

单层及多层PP蜂窝膜驻极体的压电性

经压力膨化处理后,以正逆压电系数d33测量研究了一种经无栅电晕充电的国产商用聚丙烯蜂窝膜(cellular PP,商品名PQ50)驻极体的压电性.经过优化工艺参数压力膨化处理后的PQ50蜂窝膜呈现600pC/N以上的准静态压电系数,这一量值约为PVDF相关系数的40倍.而通过将单层PQ50蜂窝膜驻极体粘贴形成合理的多层结构,得到的复合膜系压电系数d33高达2010pC/N,约为PZT压电陶瓷相应系数的3倍.从而为拓宽这类新一代的非极性孔洞聚合物压电功能膜应用领域,推动其应用进程提供了一定的理论和技术依据.     

FEP和多孔PTFE复合膜铁电驻极体的压电性及电荷动态特性

报道了将致密的FEP和多孔PTFE交互层叠在一起，采用热粘合的方法制备出具有孔洞结构的聚合物复合膜，然后经电晕极化处理使该复合膜成为铁电驻极体。最后用准静态方法测量该铁电复合膜的压电系数d33，并通过热刺激电流放电（TSD）电流谱和等温衰减研究了FEP和多孔PTFE复合膜铁电驻极体的电荷动态特性。结果表明：该复合膜的压电系数d33可达200～500pC/N，在0～12kPa的压强范围内呈现出良好的线性，并且在90℃下老化160min后仍保持在原来的43％且趋于稳定；FEP和多孔PTFE复合膜铁电驻极体电荷在热激发脱阱后复合途径主要有2种：一种是沿着固体介质的表面迁移与异性电荷复合，另一种是穿过固体介质层与异性电荷复合。在低温区（7512附近）前者占优，高温区（120℃附近）后者占优。     

微孔结构交联聚丙烯驻极体的储电性研究

压电驻极体是以双极性空间电荷驻极体为基体的新一类人工微结构压电功能材料,其压电性能与基体材料的储电性有直接关系.采用等温表面电位衰减测量和开路热刺激放电实验方法,研究了经热压处理的交联聚丙烯(XPP)膜中电荷储存稳定性和电荷动态特性.结果表明,XPP中正电荷的储存稳定性强于负电荷;在老化温度低于90℃时,经过5120min时间老化,正电晕充电样品的表面电位仍然能够维持在初始表面电位的90%以上,而负电晕充电样品却低于86%;热激发脱阱的负空间电荷在驻极体内电场的作用下迁移的过程中大部分被更深的能阱捕获,即脱阱电荷的榆运规律受快再捕获效应控制.     

孔洞结构聚丙烯铁电驻极体薄膜的压电性研究

为了提高孔洞结构聚丙烯(cellular PP)铁电驻极体的压电性能,采用高压气体膨化技术对材料进行了改性处理,并利用准静态和干涉仪测量方法,对经处理的cellular PP铁电驻极体薄膜的压电效应进行了研究.结果表明:气体膨化工艺能够明显提高cellular PP铁电驻极体薄膜的压电活性:这种突出的压电活性源干膨化膜杨氏模量Y的降低和电极化能力的提高;压电系数d33随频率的增加呈现下降趋势:从0.01 Hz下的1200 pC/N降低到共振频率附近的350 pC/N;对于不同参数处理的样品,它们的共振频率在150～400 kHz;大多数样品的d33在0.2～10 kPa的范围内没有明显的变化,但是高于10 kPa,d33随之下降;cellular PP铁电驻极体薄膜d33的热稳定性与非孔洞型PP驻极体薄膜的电荷储存热稳定性相当.     

紫外线对多孔聚四氟乙烯驻极体压电性能的影响

将恒压电晕充电的多孔聚四氟乙烯(polytetrafluoroethylene,PTFE)驻极体置于不同强度的紫外线下,研究紫外线对多孔PTFE驻极体压电活性的影响,探讨多孔PTFE医疗产品采用紫外消毒的可能性.研究结果指出(1)常温下,多孔PTFE驻极体的准静态压电系数d33随充电时间的延长而增加,并呈现出线性区、非线性区和饱和区三个区间,多孔PTFE驻极体的压电活性主要依赖于这类材料的电荷储存能力.(2)医用紫外线辐照对多孔PTFE的准静态压电系数d33的影响甚微.(3)多孔PTFE驻极体的d33随紫外辐照时环境湿度的提高而有下降,环境湿度越大,d33的下降越多.(4)紫外线辐照适合聚四氟乙烯医用驻极体产品的消毒.     

温度和湿度对聚四氟乙烯多孔驻极体膜压电活性稳定性的影响

研究了具有开放性孔洞的聚四氟乙烯(voided polytetrafluoroethylene,PTFE)多孔膜和PP蜂窝膜(polypropylene cellular)的驻极体行为和压电活性的温度效应。研究结果指出：和PP蜂窝膜驻极体相比．PTFE多孔膜驻极体呈现出突出的电荷储存和压电活性的温度稳定性;研究了这类稳定性的驻极体和材料的结构根源。PTFE多孔薄膜驻板体这种压电活性的温度稳定性主要依赖于这类驻极体材料电荷储存及材料的本征性能(如力学性质等)的温度稳定性。实验结果还说明：PTFE多孔膜突出的压电系数温度稳定性使它大大扩展了以包括PP在内的空间电荷型多孔膜研制的压电功能元器件的耐温要求。本文还讨论了环境因素(如相对湿度)对这类功能膜压电活性的影响,分析了环境湿度对压电活性影响的结构根源。     

Cement-based piezoelectret

A cement-based piezoelectret is reported for the first time. Both poling during setting and sodium silicate liquid admixture strengthened the piezoelectret effect. The electret voltage increased upon compressive strain, with partial reversibility; the voltage change was up to 450 V per unit strain (i.e., piezoelectret coupling coefficient up to 4.2 × 10⁻¹⁵ m/V). The effect was relatively strong for a Na⁺ concentration of 0.5 M in the water, in combination with a poling electric field of 225 V/m. The effect increased with increasing magnitude of the constant compressive stress. The direct piezoelectric effect was observed as a minor effect, with the voltage decreasing upon compressive strain; the voltage change was up to 6.7 V per unit strain (i.e., piezoelectric coupling coefficient down to −2.3 × 10⁻¹⁶ m/V). An Na⁺ concentration of 0.5 M gave superior performance than 1.0 M. For 0.5 M, the compressive modulus and piezoelectret coupling coefficient were higher. The poling reduced the compressive modulus and caused pore formation in the vicinity of the electrodes, but it enhanced the piezoelectret effect.     

Piezoelectric properties of (K,Na)NbO3 thin films deposited on (001)SrRuO3/Pt/MgO substrates

(K(x),Na(1-x))NbO(3) (KNN) thin films were deposited on (001)SrRuO(3)/(001)Pt/(001)MgO substrates by RF-magnetron sputtering, and their piezoelectric properties were investigated. The x-ray diffraction measurements indicated that the KNN thin films were epitaxially grown with the c-axis orientation in the perovskite tetragonal system. The lattice constant of the c-axis increased with increasing concentrations of potassium. The KNN thin films showed typical ferroelectric behavior; the relative dielectric constant epsilon(r) was 270 to approximately 320. The piezoelectric properties were measured from the tip displacement of the KNN/MgO unimorph cantilevers; the transverse piezoelectric coefficient epsilon*(31) (= d(31)/s(E)(11)) of KNN (x = 0) thin films was calculated to be -0.9 C/m(2). On the other hand, doping of potassium caused an increase in the piezoelectric properties, and the KNN (x = 0.16) films showed a relatively large transverse piezoelectricity of epsilon*(31) = -2.4 C/m(2).     

无铅压电陶瓷薄膜的制备及应用研究

无铅压电陶瓷的制备和应用是过去10年左右国际上研究的热点之一.近年来,由于无铅压电陶瓷薄膜可望在信息、传感、航空、机械、生物、医学等行业获得广泛应用,这类薄膜的制备和应用研究也已引起国际上的关注,并推动着无铅压电陶瓷薄膜材料和制备技术的不断发展.结合作者的研究工作,概括介绍了无铅压电陶瓷薄膜材料的研究进展,包括主要的无铅压电陶瓷薄膜材料;这类薄膜的主要制备方法,特别是射频磁控溅射法、脉冲激光沉积法和溶胶-凝胶法;以及无铅压电陶瓷薄膜材料可能的器件应用.     

Piezoelectric films for high frequency ultrasonic transducers in biomedical applications

Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol-gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed.     

锆钛酸铅(PZT)薄膜的自发极化与压电响应

用溶胶－凝胶法在Ｐｔ／Ｔｉ／ＳｉＯ２／Ｓｉ（１００）基片上制备了近等原子比的压电ＰＺＴ薄膜,在准同型相界附近的ＰＺＴ薄膜的应变机制是受极化控制的压电效应,内电场导致薄膜的自发极化定向,使薄膜未经极化就具有明显的压电响应。     

Improvement electrical properties of sol–gel derived lead zirconate titanate thick films for ultrasonic transducer application

In this work, a fabrication process of piezoelectric PZT [Pb(Zr_0.52Ti_0.48)O₃] thick films up to 60 μm deposited on silicon and aluminum substrates is reported. Crystalline spherical modified PZT powder about 300 nm in diameter was used as filler. PZT polymeric precursor produced by Chemat Inc. was used as the matrix material. Spinning films were annealed at 700 °C for one hour in the furnace in air. The thickness of the thick films was measured using a scanning electron microscope (SEM). Compared with previous piezoelectric PZT composite films, the modified piezoelectric thick films exhibit better dielectric properties. The dielectric constant is over 780 and dielectric loss is 0.04 at 1 KHz. Using a PiezoCAD model, the high frequency transducer was designed and fabricated. It showed a bandwidth of 75% at 40 MHz.     

Effect of water content on the piezoelectric properties of nylon 11 and nylon 7

A study of the effect of absorbed water on the piezoelectric properties of Nylon 11 and Nylon 7 films has been carried out. Films were prepared by slow cooling from the melt or by quenching rapidly into ice water. Poled films were soaked in distilledde-ionized water and the piezoelectric strain coefficientd ₃₁, piezoelectric stress coefficiente ₃₁, dielectric constant, and elastic modulusc measured continuously as the films dried out in a stream of dry nitrogen gas. The results obtained show that the piezoelectric response of poled Nylon 11 and Nylon 7 films is sensitive to adsorbed water, the sensitivity being greater for Nylon 7 than for Nylon 11. These observations are discussed in terms of the effect of water on molecular relaxation of these polymers.     

Fabrication and characterization of micromachined high-frequency tonpilz transducers derived by PZT thick films

Miniaturized tonpilz transducers are potentially useful for ultrasonic imaging in the 10 to 100 MHz frequency range due to their higher efficiency and output capabilities. In this work, 4 to 10-microm thick piezoelectric thin films were used as the active element in the construction of miniaturized tonpilz structures. The tonpilz stack consisted of silver/lead zirconate titanate (PZT)/lanthanum nickelate (LaNiO3)/silicon on insulator (SOI) substrates. First, conductive LaNiO3 thin films, approximately 300 nm in thickness, were grown on SOI substrates by a metalorganic decomposition (MOD) method. The room temperature resistivity of the LaNiO3 was 6.5 x 10(-6) omega x m. Randomly oriented PZT (52/48) films up to 7-microm thick were then deposited using a sol-gel process on the LaNiO3-coated SOI substrates. The PZT films with LaNiO3 bottom electrodes showed good dielectric and ferroelectric properties. The relative dielectric permittivity (at 1 kHz) was about 1030. The remanent polarization of PZT films was larger than 26 microC/cm2. The effective transverse piezoelectric e31,f coefficient of PZT thick films was about -6.5 C/m2 when poled at -75 kV/cm for 15 minutes at room temperature. Enhanced piezoelectric properties were obtained on poling the PZT films at higher temperatures. A silver layer about 40-microm thick was prepared by silver powder dispersed in epoxy and deposited onto the PZT film to form the tail mass of the tonpilz structure. The top layers of this wafer were subsequently diced with a saw, and the structure was bonded to a second wafer. The original silicon carrier wafer was polished and etched using a Xenon difluoride (XeF2) etching system. The resulting structures showed good piezoelectric activity. This process flow should enable integration of the piezoelectric elements with drive/receive electronics.     

力电多场鼓包法测定PZT铁电薄膜的横向压电系数

为表征Pb(Zr_(0.52)Ti_(0.48))O_3(PZT)薄膜的横向压电性能,以纯力场鼓包测试模型和铁电薄膜材料压电方程为基础,推导了PZT铁电薄膜的力电耦合鼓包本构模型。采用溶胶-凝胶法制备了PZT铁电薄膜,并通过化学腐蚀法获得PZT薄膜鼓包样品。在外加电压为0~14V的条件下进行鼓包测试。结果表明,在纯力场作用下,PZT薄膜的弹性模量和残余应力分别为91.9GPa和36.2MPa;随着电压从2V变化到14V,PZT薄膜的横向压电系数d31从-28.9pm/V变化到-45.8pm/V。本工作所发展的力电耦合鼓包测试技术及力电耦合鼓包本构模型为评价铁电薄膜材料的横向压电性能提供了一种有效的分析方法。