Influence of water-cement ratio on the properties of 2-2 cement based piezoelectric composite

Composites with 2-2 connectivity were fabricated from plates of “PMN” ceramic embedded in a sulphoaluminate cement matrix by a cut-filling process. The influences of the water-cement ratio in the matrix on the properties of the composite were analyzed. The results show that when the water-cement ratio is less than 0.4, the piezoelectric stain factor d₃₃ and piezoelectric voltage factor g₃₃ increase smoothly. When the water-cement ratio is larger than 0.4, d₃₃ and g₃₃ increase obviously with increasing the water-cement ratio. This is attributed to a more effective contact between the active and matrix phases. d₃₃ = 322 pc N^− 1 and g₃₃ = 20.9 mV mN^− 1 at a water-cement ratio of 0.45. The planar electromechanical coupling coefficient K_p of the composite is nearly independent of the water-cement ratio. With increasing the water-cement ratio, the thickness electromechanical coupling coefficient K_t of the composite increases, while the mechanical quality factor Q_m exhibits the trend of decrease.     

Shear-horizontal piezoelectric waves in an aluminum nitride film on a silicon substrate

The propagation of shear-horizontal waves in a piezoelectric film of aluminum nitride on a silicon substrate is studied. Three different electrode configurations are considered for thin film acoustic wave resonator application. A theoretical analysis is performed. The equations of linear piezoelectricity and anisotropic elasticity are used for the film and the substrate, respectively. Real and imaginary dispersion curves as well as electromechanical mode shapes are obtained. The effects of electrode configuration on the distribution of the electromechanical fields and the dispersion curves of long thickness-twist waves as well as energy trapping are examined.     

Study of vibratory behavior of interconnected porous PZT by impulse method

Performances in ultrasonic active transducers of interconnected porous lead zirconate titanate (PZT) piezoelectric disks with a porosity ranging from 30 to 70%, and polarized along their axial axis, are investigated. The characterization method used is based on the measurement of the voltage, which appears between the two faces of the piezoelectric element when it is excited by a current impulse. The device used, allows the acquisition of axial and radial vibrations of the transducer, and from these data, electromechanical and acoustic parameters are deduced. One observes that interconnected porosity causes the disappearance of the radial vibrations, and for large porosities the disk vibrates exclusively according to the axial mode. k_t is increased, the acoustic impedance is reduced, and the axial propagation velocity reaches 2500 m s⁻¹ for 30% of porosity. These results show that interconnected porous PZT are suitable for making ultrasonic active transducer, such as biomedical imaging devices.     

Design and control of a dual-stage feed drive

High precision positioning over a large workspace is a fundamental feature of a precision machine. Connecting coarse (large stroke) and fine (high resolution) drive stages, in series, to form a dual-stage feed drive (DSFD) system can provide the desired performance. The DSFD concept has applications that include fast tool servos for the creation of asymmetric surfaces or online chatter suppression, and micro–macro robots for high precision assembly. This paper studies the design of DSFDs for machine tools. The design issues are discussed with special considerations for the dynamics and control of the two drive stages. Two DSFDs, single-axis and two-axis, are designed with piezoelectric actuators (PAs) for the fine stages and linear motors (LMs) for the coarse stages. Both feature flexures for frictionless precision motion that are designed to meet the static and dynamic requirements of a milling process. A model-based control algorithm ensures that the stages work together in a complementary fashion. The single-axis DSFD reduced the tracking error by about 75% in comparison to a similarly controlled LM drive. A second DSFD was built for milling experiments. In sinusoidal profile cutting the maximum tracking error was reduced by 83% and the average magnitude of the error was reduced by 63%. In sharp corner cutting the DSFD reduced the maximum tracking error by 38% and the average magnitude of the error by 39%.     

Sliding mode control based buck-boost bidirectional converter to drive piezoelectric loads

The present work deals with the development of a converter to drive piezoelectric actuators to be used in automotive and aerospace applications and work under mechanical frequencies up to 2 kHz with rectangular, triangular and sinusoidal reference signals. In order to maximize the field in the piezoelectric ceramic important voltages (up to 2,000 V) are needed. To fulfill such requirements with a limited input voltage a bidirectional buck-boost converter is proposed. Such a converter shows voltage reduction and elevation capability. This advantage overcomes its intrinsic control non-linearity and the drawbacks involved. The converter is controlled by means of a sliding mode control strategy based on two different linked sliding surfaces which are defined as the energy error of the converter for charging and discharging operation modes, so that each surface controls one of the two switches employed. The state-space evolution of the voltage and current is investigated in order to analyze the converter limitations. The proposed converter and control strategy have been simulated and have proved to be appropriate and robust for different voltage references and values of the equivalent capacitance C _P .     

Effects of ZnO on the piezoelectric properties of Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ceramics

Perovskite-type 0.05 Pb(Mn_1/3Sb_2/3)O₃-0.95 Pb(Zr_0.5Ti_0.5)O₃ (PMS-PZT) was synthesized by conventional bulk ceramic processing technique. ZnO as a dopant up to 0.5 mol% was incorporated into the PMS-PZT system, and the effects on piezoelectric properties were investigated. Pyrochlore phase was not detected to form during the synthesis of the PMS-PZT system with 0∼0.5 mol% ZnO addition. The highest density of 7.92 g/cm³ was obtained when sintered at 1200°C for 2 hrs. Piezoelectric properties as a function of ZnO content were evaluated using a gain phase analyzer. Piezoelectric charge constant (d₃₁) and piezoelectric voltage output coefficient (g₃₁) increased up to −130 pC/N and −24.9 × 10³Vm/N, respectively, with increasing ZnO content. Mechanical quality factor (Q _m) was shown to reduce considerably with increasing ZnO content. When 0.3 mol% of ZnO was added into the system, electromechanical coupling factor (k _p) and relative dielectric constant () reached to the maximum of 56% and 1,727, respectively.     

New tools for electromechanical characterisation of piezoceramics

This paper presents three methods that can be used to characterise piezoelectric integrated structures or materials, based on the resolution of an inverse problem. Analytical models that describe the electrical and/or mechanical behaviour of the material or structure as a function of piezoelastic properties are developed, and the appropriate measurements are carried out on the piezoelectric materials. The fitting of these models with experimental data allows the piezoelastic properties to be determined. Three characterisation methods are described. The first one is based on the electrical impedance measurement of piezoelectric integrated structures. The second one, purely acoustic, is based on the measurement of transmission coefficients of a plane wave through a piezoelectric plate. The third method uses the principle of resonance ultrasound spectroscopy of a piezoelectric cube combined with Laser detection.     

A simple and powerful analytical model for MEMS piezoelectric multimorphs

We have developed an analytical model for use in design and modelling of piezoelectric MEMS devices. The model allows for incorporation of any number of device material layers in a multimorph structure including piezoelectric materials. The resulting lumped circuit model fully incorporates the electro-mechanical coupling effects in the piezoelectric layers as well as electrical or mechanical loading of the device structure. Since the model is analytic, and only requires the specification of well-defined material properties, it allows for fast and interactive modelling of a multitude of MEMS device structures incorporating piezoelectric materials. We will demonstrate the capability of the model by presenting results from fitting the model to impedance measurements performed on cantilever structures. This allows for extraction of device and material parameters that are difficult to obtain by other means, such as the piezoelectric coefficient and the mechanical quality factor.     

新型压电化学传感器的理论与应用研究

介绍了近年来在新型压电传感器方面的研究工作。液隔电极式压电传感器具有构造简单、使用寿命长的优点，能传感晶体表面质量及溶液粘度、密度、电导率、介电常数等信息。串联式压电传感器对溶液的电导率和介电常数有高灵敏的频率响应，而且具有极其优异的频率稳定性，其使用寿命可无限期地延长。压电光谱电化学技术可同时现场检测电极中有关电、光、质量三方面的信息。