PZT陶瓷/橡胶复合材料的压电性能

用PZT压电陶瓷粉末分散在无压电性的橡胶基体中制成压电复合材料。通过压电常数和介电常数测定、扫描电镜、介电谱等手段研究了有关因素对复合材料压电性能的影响。结果表明,复合材料的压电常数d₃₃随PZT体积含量φ和橡胶介电常数ε₁的增加而增大,随PZT介电常数ε₂的增加而减小,符合理论式 d₃₃=15φε₁d₃₃/(1-φ)(2+3φ)ε₂ 橡胶基体的极性基团、极性链节和交联健偶极的转向极化及分子链的柔性对复合材料的极化和压电常数有重要影响。橡胶的极性越大及分子链的柔性越高,则复合材料的压电常数d₃₃越高。      

0-3 PZT/PVDF 压电复合材料的制备及其性能

采用溶液混合法制备PZT/PVDF压电复合材料。首先用水热法制备出适合溶液混合的PZT陶瓷粉末,并根据陶瓷粉末对PVDF的吸收量,选择乙醇作为PVDF的溶剂进行混合,然后烘干制备PZT/PVDF复合粉末,再成型极化。实验结果表明,这种复合方法提高了PZT陶瓷颗粒在PVDF有机基体中的分散度,使材料内部均匀,结构致密,从而提高了PZT/PVDF压电复合材料的压电和介电性能。      

压电陶瓷粒度分布对锆钛酸铅/聚偏氟乙烯复合材料电性能的影响

将不同粒度的锆钛酸铅(PZT)陶瓷粉进行复配,制成不同粒度分布的PZT陶瓷颗粒,然后与聚偏氟乙烯(PVDF)复合制备不同PZT粒度分布的PZT/PVDF复合材料,研究了复合材料的介电性能和压电性能。结果表明,当陶瓷颗粒体积分数高达70%时,双峰分布复合材料的压电系数可达75 pC·N-1。这是由于双峰分布复合材料中大陶瓷颗粒保持了完整的钙钛矿结构,小陶瓷颗粒填充在大颗粒之间,陶瓷颗粒彼此联接,形成了更多的电-力耦合通道,有效地实现了压电效应的传递。大陶瓷颗粒完整的钙钛矿结构以及大、小颗粒的协同堆砌效应,提高了PZT/PVDF复合材料的电性能。     

Study on microstructure, piezoelectric and dielectric properties of 3-3 porous PZT composites

Porous lead zirconate titanate (PZT) composites are used for low frequency hydrophones due to their high hydrostatic figure of merit, and low sound velocity. Porous PZT composite materials manufactured using varied percentage of polymethyl methacrylate (PMMA) as a pore-forming agent was studied, to understand the effect of PMMA on microstructure and dielectric properties. Properties such as the density, porosity, transverse piezoelectric coefficient, dielectric constant, and dielectric loss factor were studied as a function of PMMA. Porous PZT composites (with 30% PMMA) show lower piezoelectric transverse coefficient (−78 pC/N) and dielectric constant (116) as compared to homogeneous PZT. At a frequency of 1 MHz, the dielectric constant decreases and dielectric loss increases with increase in PMMA. This paper describes the effect of polymethyl methacrylate (PMMA) as a pore-forming agent on dielectric properties and microstructure of porous PZT composites.     

Effects of preferred orientation on the piezoelectric properties of Pt/Pb(Zr0.3Ti0.7)O3/Pt thin films grown by sol–gel process

Tetragonal lead zirconate titanate (PZT) films with different orientations and 200 nm film thicknesses were prepared on platinized silicon substrates. Types of substrate and control of thermal processes, such as layer-by-layer and one-crystallization heat treatments, result in highly (111) or (100)-oriented PZT films. The piezoelectric, dielectric, and ferroelectric properties of polycrystalline PZT films have been investigated as a function of preferred orientation. The property difference between (111) and (100)-oriented films appears to be induced by the effect of ferroelastic domain existence (90° domain in tetragonal composition). From a modified phenomenological equation, the higher electrostrictive coefficient value of 5.6 × 10⁻² m⁴/C² for (100)-oriented PZT may be responsible for the larger piezoelectric coefficients in (100)-oriented polycrystalline PZT films of 44 pm/V in comparison to (111)-oriented PZT films with about 3.1 × 10⁻² m⁴/C² of Q ₃₃ and 40 pm/V of d _33,f . It was also observed that two (100)-oriented films prepared by different heat treatments showed different values in piezoelectric, dielectric, and ferroelectric properties even though only (100) orientation was characterized for both cases. This process-induced difference may also play an important role in determining both intrinsic and extrinsic contribution to the properties, even though these parameters seem to be more responsible for extrinsic components, such as domain wall motion.     

Performance enhancements in poly(vinylidene fluoride)-based piezoelectric films prepared by the extrusion-casting process

The extrusion-casting process can realize large-area and continuous preparation of polymer-based films. In this paper, five different types of polyvinylidene fluoride (PVDF)-based piezoelectric films: PVDF, PVDF/PZT, PVDF/PZT@105, PVDF/PZT/BNNS and PVDF/PZT@105/BNNS were prepared by the extrusion-casting process. The mechanical, dielectric, thermal conductivity and piezoelectric properties were studied. It is found that PZT particles can well improve the dielectric performance and also the mechanical stability under variable temperature conditions. PZT powders modified by titanate coupling reagent (UP-105) can further improve the performance of the PVDF/PZT@105 films by improving the combination and dispersion of organic and inorganic phases. The addition of boron nitride nanosheets (BNNS) can improve the thermal conductivity of the films and the breakdown strength. The piezoelectric coefficient (d₃₃) of PVDF/PZT@105/BNNS composite film can reach 21pC/N, compared with the neat PVDF film (4pC/N) and PZT/PVDF (9pC/N) film realizing great improvement.

     

改性PZT/PVDF体系压电复合材料的介电和压电性能

采用复合材料模压工艺,制备了体积分数不同的改性PZT(含铌的钛锆酸铅)/PVDF(聚偏二氟乙烯)压电复合材料。采用扫描电镜对材料的形貌进行了分析,并利用HP4294A,Z-3A型准静态测试仪等系统地研究了改性PZT体积分数对材料介电、压电性能的影响。结果显示,在改性PZT体积分数为70%时,获得了性能优良的压电复合材料。在压电陶瓷高含量区(>0.5),部分压电陶瓷颗粒相互联接,形成了类似0-3(3-3)型复合连通形式,是复合材料获得优良压电、介电性能的主要原因。     

成型压力对0-3型锆钛酸铅/水泥压电复合材料的影响

以快硬硫铝酸盐水泥为基体,以锆钛酸铅(PZT)为功能相,用压制成型法制备出0-3型PZT/水泥基压电复合材料。分析成型压力对PZT/水泥基压电复合材料的压电性和介电性的影响,结果表明:不同粒径PZT颗粒作为功能相的水泥基压电复合材料,成型压力对其压电性和介电性有不同的影响。在30~90 MPa压力范围内,成型压力越大,PZT/水泥压电复合材料的压电应变常数d33和相对介电常数εr均显著提高,这是由于气孔率随压力增大而减少,而压电电压常数g33的变化则与功能相的粒径有关。机电耦合系数也有着不同的变化趋势,对于6μm和126μm PZT/水泥压电复合材料,其机电耦合系数Kt和Kp随压力增大缓慢下降,而对于430μm PZT/水泥压电复合材料则呈上升趋势。当压力达到150 MPa时,其压电性和介电性均急剧减小。     

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.     

0-3型(PZT,KTN)/P(VDF-TrFE)三相铁电复合材料的电学性能

以偏氟乙烯-三氟乙烯（P（VDF-TrFE））共聚物为基体,锆钛酸铅（PZT）铁电颗粒为功能相,钽铌酸钾（KTN）颗粒为增强相,制备了0-3型（PZT,KTN）/P（VDF-TrFE）三相铁电复合材料。利用SEM及EDAX技术,分析了复合材料的显微结构及PZT和KTN相的分布。测试了具有不同KTN 体积分数的复合材料的电性能。实验结果表明:PZT和KTN相的颗粒分布均匀,存在少量的团聚体;随KTN体积分数的增加,三相复合材料的极化漏电流I、介电常数ε_r和介电损耗tanδ增加,压电系数d₃₃降低,而热释电系数p₃先增加后降低,但其d₃₃和p₃均高于具有相同PZT体积分数的PZT/P（VDF-TrFE）两相复合材料。      

Crystallite structure,microstructure, dielectric,and piezoelectric properties of (Pb1.06−xBax)(Nb0.94Ti0.06)2O6 piezoelectric ceramics prepared using calcined powders with different phases

In an attempt to obtain dense lead metaniobate-based ceramics with improved dielectric and piezoelectric properties, the (Pb_1.06−xBa_x)(Nb_0.94Ti_0.06)₂O₆ (x = 0, 0.04, 0.08, 0.12) piezoelectric ceramics were prepared separately from the two kinds of calcined powders, i.e., the powders with the rhombohedral phase and orthorhombic phase. For obtaining the calcined powders with the different phases, two different calcination temperatures of 900 °C and 1250 °C were chosen. The calcined powders were characterized using X-ray diffraction, scanning electron microscope, laser particle size analyzer and differential scanning calorimetry. Effects of the phase structures of the calcined powders on crystallite structure, microstructure, dielectric and piezoelectric properties of the ceramics were studied in detail. The lattice parameters and grain size of the ceramics are related to the phase structures of the calcined powders. The doping of Ba²⁺ has an influence on the dielectric and piezoelectric properties of the ceramics. The ceramics with x = 0.08 fabricated from the calcined powders with the orthorhombic phase demonstrate the optimum dielectric and piezoelectric properties.     

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.     

Fabrication of Lead Zirconate Titanate Powder Using Ultrasonic Ball Milling Technique

In this research, the ultrasonic ball milling technique has been used to fabricate lead zirconate titanate （PZT） ceramics. PZT with the composition nearly the morphotropic phase boundary （MPB） ： Pb（Zr0.52 Ti0.48 ）03 was studied. The effect of milling time on phase formation of sample powder was examined by X-ray diffraction technique （XRD）. Moreover, the physical, dielectric, piezoelectric properties and microstructure of PZT ceramics were investigated. The present results reveal that the ultrasonic ball milling technique results the homogeneous and small size of PZT powder. Furthermore, there is a significantly change occurs in the size of the particles with the short time of milling process.     

Piezoelectric composites of PZT and some semi-crystalline polymers

Piezoelectric composites of PZT ceramics and several semi-crystalline polymers have been produced by embedding slender PZT rods (4 volume percent) in the polymers. The observed dielectric constants were considerably lower than that of pure PZT. The hydrostatic piezoelectric voltage coefficients of the composites were larger than PZT, even though the composite hydrostatic piezoelectric strain coefficients were lower. Composite figures of merit ranged from one-third to six times that of PZT.     

Electromechanical properties of lead zirconate titanate piezoceramics under the influence of mechanical stresses

In lead zirconate titanate piezoceramics, external stresses can cause substantial changes in the piezoelectric coefficients, dielectric constant, and elastic compliance due to nonlinear effects and stress depoling effects. In both soft and hard PZT piezoceramics, the aging can produce a memory effect that will facilitate the recovery of the poled state in the ceramics from momentary electric or stress depoling. In hard PZT ceramics, the local defect fields built up during the aging process can stabilize the ceramic against external stress depoling that results in a marked increase in the piezoelectric coefficient and electromechanical coupling factor in the ceramic under the stress. Although soft PZT ceramics can be easily stress depoled (losing piezoelectricity), a DC bias electric field, parallel to the original poling direction, can be employed to maintain the ceramic poling state so that the ceramic can be used at high stresses without depoling.     

Sol-gel reaction stability studied: Influence in the formation temperature and properties of ferroelectric thin films

Lead zirconium titanate (PZT) sol-gel solutions were prepared based on distilled lead acetate precursor solutions. A detailed analysis of the distillation effect on the lead precursor and the final PZT solution were carried out by Infrared and Raman techniques. It was found that the increase in the number of distillation steps experienced by the lead precursor solutions removes the constitutional water and increases the lead acetate-2-methoxyethanol interconnectivity; thus improving stability and avoiding the aging effect of the resulting PZT solutions. The thermal decomposition process of the PZT solutions was analyzed based on the thermogravimetric (TG) and differential thermogravimetric analysis (DTA) measurements. It was found that as the number of distillation steps in the lead precursor solutions increases, the decomposition rate increases and the formation temperature of pure perovskite PZT films decreases. X-ray diffraction (XRD) technique was used to study the film phase formation. A pure perovskite phase at 500 °C was found by the XRD analysis after the second distillation step. Scanning electron microscope technique was used to carry out the microstructural analysis. Dense microstructure was found in all analyzed films and an incipient columnar grain growth was revealed in PZT films prepared based on lead precursor solution with more than three distillation steps. The dependence of the dielectric, ferroelectric and piezoelectric properties on the number of distillation steps was revealed and a correlation between the distillation process, film microstructure properties and electrical performance was established.     

Coefficients of thermal expansion for single crystal piezoelectric fiber composites

Piezoelectric fiber composites were developed to overcome drawbacks of typical monolithic piezoceramic (PZT) actuators. Although piezoelectric fiber composites had many improvements over the monolithic PZT, there are still improvements. Thus, the single crystal piezoelectric fiber composite actuator is proposed. Single crystal piezoelectric materials such as PMN-PT have larger piezoelectric strain constants, higher bandwidth and higher energy density than polycrystalline counterparts. Piezoelectric fiber composites can improve the performance of various structures, and can be subject to wide temperature range where the thermoelastic behavior is important. Therefore, this paper studies the coefficients of thermal expansion (CTE) for single crystal piezoelectric fiber composites. The Macro Fiber Composite (MFC) as the piezoelectric fiber composite is considered. To calculate the effective properties of two orthotropic layers of the MFC, PMN-PT(or PZT)/epoxy and copper/epoxy layers, the rule of mixture is adopted. With the effective properties known for each layers, the two CTE of the MFC actuator are obtained from the classical lamination theory considering thermal effects. The difference of the CTE between the single crystal MFC and the standard MFC is studied.     

Electrical properties and chemical compatibility of PZT thick film on Ni substrates

The characteristics of Pb(Zr,Ti)O₃(PZT) thick films that were printed and fired on Ni substrates were studied. The dielectric characteristics of samples sintered at 850°C on Ni substrates could not be measured due to the formation of a NiO layer at the Ni/PZT interface. The scanning electron microscope and energy dispersive X-ray analysis of cross-sections of the PZT thick films on Ni substrates, and of a mixture of PZT and NiO powders, fired at 850°C, did not indicate the formation of secondary phases. However, the transmission electron microscopy showed around 8% solid solubility of NiO in the PZT. A new structure with a prefired, Au thick-film layer was designed in order to prevent the diffusion of the NiO to the PZT layer during sintering. The dielectric properties of the PZT layers printed and fired on the Ni substrates with the prefired Au electrode were significantly better than those of the layers on the uncoated substrate, the dielectric losses decreased from 0.23 to 0.05.     

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.     

PZT-epoxy piezoelectric transducers: A simplified fabrication procedure

Composite piezoelectric transducers have been constructed by partially dicing PZT ceramics and back-filling with epoxy. Composites containing 10 to 70 volume percent PZT were prepared with several different rod diameters. Measured dielectric constants ranged from 200 to 1000, longitudinal piezoelectric coefficients d₃₃ from 200 to 350 pC/N, and hydrostatic piezoelectric coefficients d_h from 40 to 80 pC/N. Piezoelectric properties are compared with solid PZT and with 3-1 composites made by extrusion.