Fabrication and comparison of PMN-PT single crystal, PZT and PZT-based 1-3 composite ultrasonic transducers for NDE applications

This paper describes fabrication and comparison of PMN-PT single crystal, PZT, and PZT-based 1-3 composite ultrasonic transducers for NDE applications. As a front matching layer between test material (Austenite stainless steel, SUS316) and piezoelectric materials, alumina ceramics was selected. The appropriate acoustic impedance of the backing materials for each transducer was determined based on the results of KLM model simulation. Prototype ultrasonic transducers with the center frequencies of approximately 2.25 and 5 MHz for contact measurement were fabricated and compared to each other. The PMN-PT single crystal ultrasonic transducer shows considerably improved performance in sensitivity over the PZT and PZT-based 1-3 composite ultrasonic transducers.     

Micromachined high frequency PMN-PT/epoxy 1-3 composite ultrasonic annular array

This paper reports the design, fabrication, and performance of miniature micromachined high frequency PMN-PT/epoxy 1-3 composite ultrasonic annular arrays. The PMN-PT single crystal 1-3 composites were made with micromachining techniques. The area of a single crystal pillar was 9 × 9 μm. The width of the kerf among pillars was ∼5 μm and the kerfs were filled with a polymer. The composite thickness was 25 μm. A six-element annular transducer of equal element area of 0.2 mm² with 16 μm kerf widths between annuli was produced. The aperture size the array transducer is about 1.5 mm in diameter. A novel electrical interconnection strategy for high density array elements was implemented. After the transducer was attached to the electric connection board and packaged, the array transducer was tested in a pulse/echo arrangement, whereby the center frequency, bandwidth, two-way insertion loss (IL), and cross talk between adjacent elements were measured for each annulus. The center frequency was 50 MHz and −6 dB bandwidth was 90%. The average insertion loss was 19.5 dB at 50 MHz and the crosstalk between adjacent elements was about −35 dB. The micromachining techniques described in this paper are promising for the fabrication of other types of high frequency transducers, e.g. 1D and 2D arrays.     

Thermo-mechanical stress effect on 1-3 piezocomposite power transducer performance

This paper deals with the emission performance of 1-3 piezoelectric composite power transducers made with a hard PZT (Navy III) and epoxy resins with a high glass-rubber transition temperature. Following the "dice and fill" technique, various composite transducers with 30 and 50% PZT volume fractions were fabricated with an air backing and no front matching layer with resonance operating frequencies around 500 kHz. The transducers were first evaluated under isothermal conditions, with a low emission duty cycle. Efficiencies as high as 95% were monitored as a function of the instantaneous input power up to a 60 W/cm(2) density. The effect of the polymer matrix mechanical losses and the fabrication conditions is then discussed. For the transducer thermal stability, the case of long duty cycle or continuous emission was considered in a second evaluation. In this case the transducer working temperature and axial radiated pressure were monitored as functions of the input power density up to 40 W/cm(2). It is shown that the transducer efficiency and working temperature were strongly dependent on the type of resin used but also on the PZT material, even for hard PZT compositions. A composite transducer configuration with strongly improved thermal stability was investigated demonstrating a working temperature higher than 90 degrees C and an extended power range (30-40 W/cm(2)). The composite thermal breakdown mechanism was analyzed and the effect of the curing-induced thermo-mechanical stresses on the PZT mechanical losses was considered in relation to the composite working temperature. Measurements of the composite mechanical losses versus the temperature were obtained and related to the variation of the PZT mechanical losses with the stresses due to the composite transducer temperature change. It is found that the thermally induced stress can strongly influence the PZT ceramic mechanical losses and that it can be the reason for a thermal breakdown taking place at a temperature much lower than the epoxy resin transition.     

Piezoelectric PMN-PT fibre hydrophone for ultrasonic transducer calibration

A newly developed ceramic fibre hydrophone with an active element as small as 0.25 mm in diameter is described in this work. Lead magnesium niobate-lead titanate (PMN-PT) ceramic fibre with a nominal composition of 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃ was fabricated by an extrusion method. PMN-PT single crystals were ground to a powder form and then mixed with poly(acrylic) acid to form a homogenous slurry. The fibre was extruded by pressing the slurry through a spinneret and then sintering at 1250 °C for crystallization. The electrical characteristics of the PMN-PT fibre were evaluated by measuring the relative permittivity and the impedance spectrum. A piezoelectric PMN-PT fibre hydrophone was fabricated and its sensitivity, angular response, and spatial resolution were evaluated. The fibre hydrophone provides good spatial resolution, angular response and receiving sensitivity. PACS 43.58.+z; 77.84.Dy     

高频宽带嵌套式复合材料换能器*

研制了一种嵌套式高频宽带复合材料换能器,利用1-3型压电复合材料Q值较低、频带较宽的特点,采用组合式的结构拓展换能器的工作带宽。通过切割框型压电陶瓷、灌注环氧树脂得到压电复合材料框型敏感元件,再将不同厚度的框型敏感元件沿轴向嵌套从而制成多层嵌套的压电复合材料敏感元件。建立1-3型压电复合材料中压电小柱的等效电路,根据等效电路计算出压电小柱的谐振频率,并与1-3型压电复合材料的谐振频率理论计算结果进行对比。通过ANSYS软件对敏感元件结构进行仿真,并根据仿真结果确定了敏感元件的最佳设计方案。最终制作出的换能器进行水下测试,该换能器的谐振频率为310kHz,最大发送电压响应为188.5dB,-3dB带宽可达130kHz,接收灵敏度最大可达-186.8dB,-3dB带宽可达90kHz,谐振频率处-3dB的指向性开角约为2.4°。该嵌套式敏感元件可实现换能器宽带发射与接收声波的目标。     

Lead-free BNBT-6 piezoelectric ceramic fibre/epoxy 1-3 composites for ultrasonic transducer applications

Barium-modified bismuth sodium titanate, 0.94 ×(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃ (BNBT-6), fine-scale piezoelectric fibres were fabricated using a viscous suspension spinning process (VSSP). The sintered BNBT-6 fibres with diameters of 300 m were fabricated into 1-3 composites with fibre volume fraction v_f of 0.2–0.5. Piezoelectric and dielectric properties of the 1-3 composites were measured. The electromechanical coupling coefficient k_t of a v_f=0.40 composite is 0.52. Properties of the VSSP fibres were calculated using the measured properties of the 1-3 composites. A v_f=0.40 composite was thinned down to 213-m thickness and constructed into an ultrasonic transducer. The pulse-echo response, bandwidth and insertion loss of the transducers were studied. The VSSP fibre composite transducer with v_f=0.40 has a centre frequency of 7 MHz with a bandwidth of 88%. The good performance indicated that the BNBT-6/epoxy 1-3 fibre composite transducer has potential for medical imaging applications. PACS 77.84.Dy; 77.84.Lf; 43.38.+n     

PMN-PT single crystal focusing transducer fabricated using a mechanical dimpling technique

A ∼5 MHz focusing PMN-PT single crystal ultrasound transducer has been fabricated utilizing a mechanical dimpling technique, where the dimpled crystal wafer was used as an active element of the focusing transducer. For the dimpled focusing transducer, the effective electromechanical coupling coefficient was enhanced significantly from 0.42 to 0.56. The dimpled transducer also yields a −6 dB bandwidth of 63.5% which is almost double the bandwidth of the plane transducer. An insertion loss of the dimpled transducer (−18.1 dB) is much lower than that of the plane transducer. Finite element simulation also reveals specific focused beam from concave crystal surface. These promising results show that the dimpling technique can be used to develop high-resolution focusing single crystal transducers.     

Selecting passive and active materials for 1.3 composite power transducers

1.3 PZT-polymer composites were fabricated using the dice and fill method with various PZT types and volume fractions. These composites were evaluated for power underwater transducer applications with an air backed and no matching layer configuration. Electrical input and acoustical output powers were monitored as a function of the drive level. Total acoustic power densities of 30 W/cm2 were obtained with a P189/epoxy piezocomposite vibrating at 350 kHz with a low duty cycle (1-5%) and with a 90% efficiency. Power densities up to 20 W/cm2 were measured with a 50% duty cycle. Evolution and destruction of the transducers were monitored versus increasing averaged power. It was observed that better efficiencies were obtained with low volume fraction configurations allowing natural acoustic impedance matching to water. It was found that hard PZT type (Navy III) are optimal compositions even for piezocomposite transducers. It is shown that, unlike a common belief, the polymer mechanical losses are comparable to those of the active ceramic justifying that 1.3 piezocomposites are suited for low-cost power applications. In fact, the main limitation induced by the polymer phase is a strong thermal breakdown when the temperature of the transducer approaches the glass transition region of the polymer. Measurements of the polymer losses as a function of the temperature were obtained confirming this point and offering interesting new alternatives for future composite power transducers.     

一种高灵敏压电平面水声换能器

设计并制作了一种高灵敏压电平面水声换能器。该换能器敏感元件是对1-3-2型压电复合材料结构的改进,即在带基底的压电陶瓷小柱阵列间不注入聚合物,并在其上表面直接覆盖金属板,构成“带基底的压电小柱阵列+金属盖板”结构敏感元件(称为“空气填充型”敏感元件)。对“空气填充型”敏感元件的谐振频率进行了理论计算和有限元仿真,与实测结果较吻合。为便于对比性能,同时制作了同尺寸“1-3-2型压电复合材料+金属盖板”结构敏感元件(称为“聚合物填充型”敏感元件)换能器。分别对“空气填充型”和“聚合物填充型”敏感元件换能器的有效机电耦合系数、发送电压响应和接收灵敏度进行有限元仿真和实测,结果均显示,“空气填充型”敏感元件换能器具有较高的接收灵敏度,相较于“聚合物填充型”敏感元件换能器可提高21 dB。该敏感元件换能器能有效提高灵敏度,可为研制高灵敏换能器提供参考。      

电泳辅助制备伪1-3陶瓷/聚合物压电复合材料

1-3压电复合材料的压电、介电及铁电性能要远远优于0-3压电复合材料.在制备传统的0-3复合材料过程中引入电泳技术,使得压电颗粒在聚合物基体中取向排列,制备得到伪1-3复合材料.实验结果表明:在制备PZT/环氧树脂0-3复合压电材料固化过程中,采用500 V/mm,4 kHz的电场对其进行电泳辅助取向,可使得颗粒呈现珍珠串状排列,得到伪1-3复合材料;其压电、介电、铁电性能均比原来的0-3复合材料有显著的提高.电泳辅助制备技术用于制备伪1-3复合压电材料具有操作简单、成本低廉、压电、介电、铁电性能显著提高等优点,在智能传感领域具有很好的实际应用前景.     

Study of 1-3-2 type piezoelectric composite transducer array

Based on a new structure of precise location and decoupling between the transducer elements, high frequency underwater transmission transducer arrays with 4 elements and 8 elements serried uniform linear array were studied, using novel 1-3-2 type piezoelectric composite as the sensing material. There are ceramic framework supports in the transverse and longitudinal directions in 1-3-2 type piezoelectric composite structure; the transducer is free from the influence of outside mechanical impact and the environment temperature change. Transducer and array samples have been designed, fabricated and measured. The resonant frequency is 150 kHz, resonant transmission response greater than 160 dB, and bandwidth is from 140 kHz to 160 kHz. The results indicate that, the transducer array has wide bandwidth, high sensitivity, stabile performance, and good coherence.     

Synthesis and structural characterization of perovskite 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 nanotubes

We report the synthesis and structural characterization of 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃ (PMN-PT) nanotubes prepared by a novel sol-gel template method. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) investigations demonstrated that the postannealed (650 °C for 1 h) PMN-PT nanotubes were polycrystalline with perovskite crystal structure. The field emission scanning electron microscope (FE-SEM) shows that as prepared PMN-PT nanotubes were hollow with diameter to be about 200 nm. High resolution transmission electron microscope (HRTEM) analysis confirmed that the obtained PMN-PT nanotubes made up of nanoparticles (10-20 nm) which were randomly aligned in the nanotubes. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the stoichiometric 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃. The possible formation mechanism of PMN-PT nanotubes was proposed at the end.     

Thermal and Mechanical Properties of Epoxy/Carbon Fiber Composites Reinforced with Multi-walled Carbon Nanotubes

Multi-scale hybrid composite laminates of epoxy/carbon fiber (CF) reinforced with multi-walled carbon nanotubes (MWCNTs) were fabricated in an autoclave. For laminate fabrication, 0.5 wt% of pristine MWCNTs or silane-functionalized MWNCTs (f-MWCNTs) were dispersed into a diglycidyl ether of bisphenol-A epoxy system and applied on the woven carbon fabric. The neat epoxy/CF composite and the MWCNTs-reinforced epoxy/CF hybrid composites were characterized by thermogravimetric analysis (TGA), thermomechanical analysis (TMA), tensile testing, and field emission scanning electron microscopy (FE-SEM). A significant improvement in initial decomposition temperature and glass transition temperature of epoxy/CF composite was observed when reinforced with 0.5 wt% of f-MWCNTs. The coefficient of thermal expansion (CTE), measured by TMA, diminished by 22% compared to the epoxy/CF composite, indicating an improvement in dimensional stability of the hybrid composite. No significant improvement in tensile properties of either MWCNTs/epoxy/CF composites was observed compared to those of the neat epoxy/CF composite.     

Study of 1-3 PZT fibre/epoxy composite force sensor

Lead zirconate titanate (PZT) fibres were prepared by a powder-based extrusion method. Pre-sintered PZT powder mixed with poly(acrylic acid) was spun in a spinnerette to produce fibres. The fibre of ∼400 μm diameter was used to fabricate 1-3 PZT fibre/epoxy composite discs with different volume fractions (ϕ) of PZT. Since the ceramic fibres are rather brittle, their elastic properties cannot be measured directly. In order to determine the properties of the ceramic fibres, effective properties of the fibres/epoxy 1-3 composite were measured. By using a modified series and parallel model, the properties of 1-3 composites can be calculated. Then, the elastic coefficient s_33,fibre^E, relative permittivity ε_33,fibre^T and piezoelectric strain coefficient d_33,fibre of the ceramic fibre could be found. Ring-shaped PZT fibre/epoxy materials composites with different ϕ were fabricated to be used as the sensing material in force sensor applications. The ring-shape composite with ϕ=0.5 was installed into a housing and the sensor was calibrated by different methods and its sensitivity was found to be 144 pC/N within the frequency range of 0.5–6.4 kHz which is much higher than that of a quartz force sensor with a similar structure. PACS 07.07.Df; 72.80.Tm; 77.84.Dy     

具有大指向性开角及高发射电压响应的发射换能器

应用复合变幅杆及夹心式换能器结构,研制了一种指向性开角较大且发射电压响应较高的发射换能器。应用有限元方法对换能器的工作频率,发射电压响应及指向性进行了理论计算。并与实验结果进行了比较,结果较吻合。本文研制的换能器工作频率为75.6kHz,发射电压响应级达到1 56dB(基准值1V/μPa),-3dB发射指向性开角100°     

基于PbMg_(1/3)Nb_(2/3)O_3-PbTiO_3压电单晶的磁电复合薄膜材料研究进展

电子信息技术的迅速发展对磁电功能器件的微型化、智能化、多功能化以及灵敏度、可靠性、低功耗等都提出了更高的需求,传统的块体磁电功能材料已日渐不能满足上述需求,而层状磁电复合薄膜材料同时具有铁电性、铁磁性和磁电耦合等多种特性,因此能满足上述需求且有望应用于新一代磁电功能器件.层状磁电复合材料不仅具有非常丰富的物理现象和效应,而且在弱磁探测器、多态存储器、电写磁读存储器、电场可调低功耗滤波器、移相器、天线等微波器件中也具有广阔的应用前景,因而受到材料科学家和物理学家广泛的关注和研究.在层状磁电复合材料中,功能薄膜/铁电单晶异质结因其制备简单、结构设计和材料选择灵活以及电场调控方便和有效,最近十余年引起了越来越多的研究人员的兴趣.目前,以具有优异铁电和压电性能的(1-x)PbMg_(1/3)Nb_(2/3)O_3-PbTiO_3(PMN-PT)单晶作为衬底,构建功能薄膜/PMN-PT异质结已成为国内外多铁性复合薄膜材料研究领域的重要方向之一.相比于其他国家,我国科学家无论在发表的文章数量还是在文章被引用次数方面都处于领先地位,表明我国在功能薄膜/PMN-PT单晶异质结方面的研究卓有成效.迄今为止,研究人员已构建了锰氧化合物/PMN-PT、铁氧体/PMN-PT、铁磁金属/PMN-PT、稀磁半导体/PMN-PT、发光材料/PMN-PT、二维材料/PMN-PT、多层薄膜/PMN-PT、超导薄膜/PMN-PT等多种类型的异质结,在理论研究和实验方面都取得了丰富的研究成果.本文对基于PMN-PT压电单晶的磁电复合薄膜材料的研究进展进行了总结:简要介绍了与功能薄膜/PMN-PT异质结相关的研究论文发表现状;介绍了PMN-PT单晶在准同型相界附近的相图和应变特性;按照功能薄膜材料所属的体系对异质结进行了分类,并选取部分代表性的研究成果,介绍了材料的磁电性能和内涵的物理机制;最后就目前有待解决的问题和未来可能的应用方向进行了总结和展望.     

1-3型压电复合材料非均匀振动换能器的研究

通过调整１－３型压电复合材料换能器中压电相的分布，可以控制换能器辐射面上振动幅度和相位的分布，从而获得具有特殊性能的声场。     

1-3型压电复合材料非均匀振动换能器的研究

通过调整1－3型压电复合材料换能器中压电相的分布，可以控制换能器辐射面上振动幅度和相位的分布，从而获得具有特殊性能的声场．作为辐射源表面振动速度等相位不等幅和等幅不等相位的两种典型情况，本文对边线高斯型换能器和Wesnel聚焦换能器进行了实验研究，讨论了其声场特性．     

Cymbal piezoelectric composite underwater acoustic transducer

The working principle of Cymbal piezoelectric composite underwater acoustic transducer was studied in this paper. PZT-5A piezoelectric ceramic disk was used as piezoelectric phase and brass foil was used as end cap electrode of the Cymbal transducer. The silicon rubber was used as the insulated proof layer of the underwater acoustic transducer. The properties of this transducer used as hydrophone, such as operation frequency, free-field voltage receiving sensitivity and directivity, were investigated. Several kinds of prototype of this transducer were fabricated and the properties of this transducer used as hydrophone were tested. The results show that the properties of this transducer used as hydrophone depend on the dimensions of Cymbal transducer because the piezoelectric properties of this transducer are dependent on the dimensions of Cymbal transducer's end caps. The appropriate dimensions for getting higher free-field voltage receiving sensitivity with -184.7 dB were obtained.     

High-frequency PIN–PMN–PT single crystal ultrasonic transducer for imaging applications

A high-frequency (～60 MHz) ultrasonic transducer with a [001]-oriented 0.27Pb(In_1/2Nb_1/2)O₃–0.45Pb(Mg_1/3Nb_2/3)O₃–0.28PbTiO₃ (PIN–PMN–PT) piezoelectric single crystal as an active element has been fabricated and characterized. The poled PIN–PMN–PT single crystal has thickness mode electromechanical coefficient k _t of 0.56 and piezoelectric constant d ₃₃ of 1550 pC/N. The ?6 dB bandwidth of the transducer is 73 % and the insertion loss at its centre frequency is ?20 dB. With the study as a function of temperature, the PIN–PMN–PT transducer shows better thermal stability than the binary single crystal transducer. Furthermore, the transducer was evaluated using a 30-μm aluminum wire phantom image, in which the ?6 dB axial and lateral resolutions are found to be 26 μm and 127 μm, respectively. Ultrasonic images of fish eyes were obtained with the 60-MHz transducer. It is shown that the high-sensitivity transducer can produce the images with high signal-to-noise ratio and good contrast.