Micromachined piezoelectric force sensors based on PZT thin films

A micromachined lead zirconate titanate (PZT) force sensor for scanning force microscope (SFM) is conceptualized by its piezoelectricity. The fabrication procedure is interpreted, and mechanical characteristics of the micromachined PZT force sensors with various lengths are studied in this paper. A compact SFM is constructed by using the piezoelectric PZT sensor. A very clear image is taken by this SFM. The current study of the micromachined PZT force sensor can be considered as a breakthrough of design of SFM as well as a good example of integrated piezoelectric microdevices     

Elastic surface wave devices based on piezoelectric thick-films

A study has been performed for the development of elastic-waves structures, involving screen printed and fired piezoelectric layers on nonpiezoelectric substrates, intended for new families of thick film sensors. This study approached the electroacoustic effects, i.e., the coupling between electromechanical parameters of the layers and elastic properties of the substrate, related to the wave propagation. In this work, particular attention is devoted to devices implemented on alumina substrates where SAW as well as (symmetric and antisymmetric) Lamb's waves are generated. The realization processes and the performance characteristics of these structures are presented     

PZT压电薄膜无阀微泵

介绍了一种基于PZT压电薄膜的无阀压电微泵.该微泵利用自制的压电圆型薄膜片作为驱动部件、聚二甲基硅氧烷(PDMS)作为泵膜.本文在对微豕制备工艺研究的基础上,对其性能进行了数值和实验研究.建立了基于扩张管/收缩管理论的无阀微泵的有限元模型.利用MFX-AN-SYS/CFX技术实现了对微泵的双向流固耦合分析.对微泵的锥形角、最小宽度、扩散管长度、泵腔高度进行数值计算,得到了优化参数.数值计算的结果与实际测量的数据进行了比较,验证了仿真的正确性.     

Multilayer modal actuator-based piezoelectric transformers

An innovative, multilayer piezoelectric transformer equipped with a full modal filtering input electrode is reported herein. This modal-shaped electrode, based on the orthogonal property of structural vibration modes, is characterized by full modal filtering to ensure that only the desired vibration mode is excited during operation. The newly developed piezoelectric transformer is comprised of three layers: a multilayered input layer, an insulation layer, and a single output layer. The electrode shape of the input layer is derived from its structural vibration modal shape, which takes advantage of the orthogonal property of the vibration modes to achieve a full modal filtering effect. The insulation layer possesses two functions: first, to couple the mechanical vibration energy between the input and output, and second, to provide electrical insulation between the two layers. To meet the two functions, a low temperature, co-fired ceramic (LTCC) was used to provide the high mechanical rigidity and high electrical insulation. It can be shown that this newly developed piezoelectric transformer has the advantage of possessing a more efficient energy transfer and a wider optimal working frequency range when compared to traditional piezoelectric transformers. A multilayer piezoelectric, transformer-based inverter applicable for use in LCD monitors or portable displays is presented as well.     

PZT系梯度功能压电驱动器的谐响应特性

研究了PZT系梯度功能压电驱动器谐振状态的机电响应特性，通过改变驱动电场和频率，研究其谐振频率和顶端位移的变化特性。结果表明：增加电场，谐振频率减小，谐振点位移增大，并逐渐趋向饱和。在谐振点附近，悬臂梁弯曲位移达到最大值。     

水热法合成PZT粉体的研究

以硝酸铅、氧氯化锆、钛酸四丁酯为反应物前躯体,氢氧化钾为矿化剂,采用水热法合成PZT粉体.系统研究了反应温度、反应时间、矿化剂浓度和引入表面活性剂聚乙烯醇(PVA)对PZT晶体生长的影响.通过XRD和SEM对粉体进行了表征,探索出制备PZT粉体的最佳条件,研究结果表明:在KOH浓度为2 mol/L、180℃反应12 h的条件下可制备得到粒径约为1μm,粒径均匀,晶体发育完整的钙钛矿结构的PZT粉体;在该反应体系中加入适量PVA时得到了棒状纤维结构的粉体.     

Multilayer piezoelectric resonators for medical ultrasoundtransducers

Multilayer piezoelectric resonators were fabricated and the dependence of the electrical impedance and the coupling coefficient were measured as a function of the number of layers, for N=1, ···, 20 layers. The magnitude of the electrical impedance followed the theoretical predicted 1/N² relation, and the coupling coefficient, K_t, remained relatively constant out to N=15 layers. These cofired resonators are suitable for medical ultrasound transducers     

铈掺杂对PZT压电陶瓷性能的影响

研究了铈掺杂对PZT(锆钛酸铅)压电陶瓷材料的相组成、微观结构、介电性能、压电性能及铁电性能的影响,并对实验结果做出物理机理的解释.实验结果表明,适量的铈掺杂有利于材料结构的致密,提高了体电阻率,解决了材料在高温高场下极化困难的问题,在铈掺杂量为0.4%(摩尔分数)时,制备出综合性能良好的PZT压电陶瓷:室温时εr=958,tgδ=0.24%,d33=239pC/N,Kp=0.45,Qm=886,适合制备大功率压电陶瓷.     

Electrical power generation characteristics of PZT piezoelectric ceramics

The electrical power generation characteristics of Mn-doped PZT ceramics responding to slow mechanical stress as well as to impact stress have been investigated. Although both the slow and impact stresses induce a reversible electrical response, the generation properties are distinctly different. Slow stress releases two output current peaks with opposite directions, responding to the increasing and decreasing part of the stress, respectively. However, impact stress produces a nearly one-directional signal. The output charge and energy by slow stress are found to be two orders of magnitude higher than that produced by impact stress. This work shows that the energy conversion efficiency of piezoelectric ceramics strongly depends on the method of stress application.     

Multilayer piezoelectric ceramics for two-dimensional array transducers

In medical ultrasound imaging, 2-D array transducers have become essential to implement dynamic focusing and phase-correction in the elevation dimension as well as real-time volumetric scanning. Unfortunately, the small size of a 2-D array element results in a small clamped capacitance and a large electrical impedance near resonance. These elements have poor sensitivity because their impedance is much higher than the electrical impedance of the transmit and receive circuitry. Sensitivity can be improved by using an N layer structure of PZT ceramic with the layers connected acoustically in series and electrically in parallel. For the multilayer ceramic (MLC), the damped capacitance is multiplied by a factor of N(2) and the electrical impedance by 1/N(2) compared to a single layer element of the same dimensions. A 3x43 phased-array transducer has been fabricated using 3 layer PZT-5H material. Each element had a thickness of 0.66 mm and an area of 0.37x3.5 mm. The MLC was manufactured using thick film technology with plated-through vias to electrically interconnect the electrode layers. The completed transducer was compared to a single layer control array of similar dimensions. With a light epoxy backing and a lambda/4 matching layer, the MLC array elements had an impedance of 100 Omega at series resonance of 2.25 MHz, compared to 800 Omega for the control elements. The lower impedance of the MLC elements resulted in a minimum round-trip insertion loss of 24.0 dB, compared to an 34.1 dB for the control array elements. These results were consistent with KLM modeling. B-scan images were made of cysts in a tissue-mimicking phantom and of the left kidney in vivo. The images clearly showed a higher signal-to-noise ratio for the MLC array compared to the control. As a result, 2-D arrays made of multilayer ceramics can be used to form images at a higher frequency and greater range than single layer arrays.     

Resonance behavior of internally electroded PZT devices

Preparation and resonant properties of hard and soft internally electroded PZT bars are described. The presence of cofired platinum internal electrodes is shown to have little effect on the resonance behavior of hard PZT. Piezoelectric transformers having internally electroded primaries and secondaries are compared with conventional devices and show improved transformer ratio and power handling capability.     

Meshless analysis of piezoelectric devices

 The sensor and actuator properties of piezoelectric materials make them well suited for applications in a variety of microelectromechanical systems (MEMS). Simulating the response of piezoelectric devices requires solving coupled electrical and mechanical partial differential equations. In this paper, we have implemented a meshless point collocation method (PCM) to solve the governing equations. Interpolation functions are constructed from a reproducing kernel approximation, and the governing equations are discretized using a collocation approach. PCM is implemented using either a relaxation algorithm or a fully-coupled algorithm. Comparisons between the two algorithms are given. To demonstrate the performance of PCM, the behavior of two static single-layer problems and a piezoelectric bimorph have been modeled. The bimorph analysis is extended to model a prototype MEMS device. Received: 6 June 2000     

铟掺杂PZT铁电陶瓷性能研究

采用传统固相烧结法制备In2O3掺杂的锆钛酸铅(PZT)铁电陶瓷,研究了In2O3掺杂量对PZT铁电陶瓷材料的相组成、微观结构、介电性能、压电性能及铁电性能的影响。研究结果表明,随着In2O3掺杂量的增加,PZT材料在准同型相界处三方相增加四方相减少,适量掺入In2O3有利于晶粒均匀生长。在不同的铟掺杂剂量下,PZT陶瓷材料分别具有最佳的铁电及压电性能。当铟掺杂量为0.1%(质量分数)时,PZT材料具有最佳的铁电性能,其剩余极化强度为23.43μC/cm2,矫顽场为9.783kV/cm。当铟掺杂量为0.3%(质量分数)时,PZT材料具有最好的压电性能,其tanδ=0.023,d33=540pC/N,εr=1513,Kp=0.764,Qm=1819。     

Influence of poling conditions on the piezoelectric properties of PZT ceramics

The influence of the poling temperature, the poling electric field, the poling time and the distance between electrodes on the dielectric constant _r and the electro-mechanical coupling factor k_r of PZT were investigated using a statistical analysis method. Interactions between various factors affecting _r and k_r parameters were found particularly, with regard to the poling temperature. The k_r value of PZT is influenced more by the absolute voltage than by the applied electric field strength.     

Multilayer piezoelectric ceramic transformer with low temperature sintering

The low-fired high performance piezoelectric ceramics used for multilayer piezoelectric transformer were investigated. Based on the transient liquid phase sintering mechanism, by doping suitable eutectic additives and optimizing processing, the sintering temperature of the quaternary system piezoelectric ceramics with high piezoelectric properties could be lower to about 960–1000°C. The low-temperature sintering multilayer piezoelectric transformer (MPT) has been developed. Some characteristics of MPT were systemically studied. The measurements include the frequency response of input impedance, frequency response of phase difference between input voltage and current, frequency shifting with load, input impedance changing with load, phase difference between input voltage and current shifting with load, and phase difference between input voltage and vibration velocity. The vibration modes and resonance characters of MPT were measured by a Laser Doppler Scanning Vibrometer. Several kinds of MPT with high voltage step-up ratio, high power density, high transfer efficiency and low cost have been industrially produced and commercialized. It reveals a broad application prospect for back-light power of liquid crystal display and piezo-ionizer etc.     

Experimental and theoretical study on the piezoelectric behavior of barium doped PZT

An experimental and theoretical study of the ferroelectric and piezoelectric behavior of PZT doped with barium is presented. Ab initio perturbed ion calculations was carried out. The properties, such as remnant polarization, coercive field and the coupling factor of the PZT at constant sintering temperature was compared with the Zr⁴⁺/Ti⁴⁺ ions dislocation energy and the lattice interaction energy. An agreement between the experimental and theoretical results, with a decrease of the interaction energy and an inversion of the energy stability from tetragonal to rhombohedral phase was observed.     

Multilayer processing for magnetic film memory devices

Planar processing techniques for producing coupled film storage devices are presented. The discussion centers around a process sequence for a coupled easy-axis structure built on a metal substrate, largely by vacuum deposition techniques. The process results in packing density of about 8000 bits/in². Included is a test of one such element displaying useful memory device characteristics under conditions of a worst case pulse test program.     

Dielectric and piezoelectric properties of the mechanochemically prepared PZT ceramics

Mechanochemical synthesis was applied to obtain nanocrystalline powders of composition Pb(Zr_0.52Ti_0.48)O₃ (PZT). Milling was performed in a planetary ball mill using vials and balls made of zirconia or steel in order to investigate influence of milling media on the electrical properties of resulting ceramics. PZT ceramics showed high values for dielectric constant (∈_r), reaching 970 at room temperature, as well as low dielectric loss (tanδ) under the optimal processing conditions. High values of remanent polarization (P _r) indicate high internal polarizability. The best samples showed piezoelectric strain constant d ₃₃ = 347 pC/N and planar coupling factork _P = 0.44. Milling in ZrO₂ medium prevents powder contamination and provides reproducibility of milling process. Also, PZT obtained from the powders milled in ZrO₂ exhibited lower values of dielectric loss, in comparison with the PTZ obtained from the powders milled in Fe. This suggests that contamination of the powder with Fe could result in an increase of conductivity in final product.